182-478: Justus Freiherr von Liebig (12 May 1803 – 20 April 1873) was a German scientist who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and biological chemistry ; he is considered one of the principal founders of organic chemistry . As a professor at the University of Giessen , he devised the modern laboratory-oriented teaching method, and for such innovations, he
364-478: A Kaliapparat , to trap the oxidation product of the carbon in the sample following its combustion. Before reaching the Kaliapparat, the combustion gases were conducted through a tube containing hygroscopic calcium chloride , which absorbed and retained the oxidation product of the hydrogen of the sample, namely water vapor. Next, in the Kaliapparat, carbon dioxide was absorbed in a potassium hydroxide solution in
546-525: A last universal common ancestor that lived about 3.5 billion years ago . Geologists have developed a geologic time scale that divides the history of the Earth into major divisions, starting with four eons ( Hadean , Archean , Proterozoic , and Phanerozoic ), the first three of which are collectively known as the Precambrian , which lasted approximately 4 billion years. Each eon can be divided into eras, with
728-440: A lipid bilayer , including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. Cell membranes are semipermeable , allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions . Cell membranes also contain membrane proteins , including integral membrane proteins that go across
910-443: A nucleus , and prokaryotic cells, which do not. Prokaryotes are single-celled organisms such as bacteria , whereas eukaryotes can be single-celled or multicellular. In multicellular organisms , every cell in the organism's body is derived ultimately from a single cell in a fertilized egg . Every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space . A cell membrane consists of
1092-504: A number of shapes , ranging from spheres to rods and spirals . Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats . Bacteria inhabit soil, water, acidic hot springs , radioactive waste , and the deep biosphere of the Earth's crust . Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about 27 percent of
1274-486: A bodyguard of the Grand Duke of Hessen-Darmstadt, for an entire month. He outlined an extremely speculative model of equations in which he attempted to explain how protein degradation might balance within a healthy body and result in pathological imbalances in cases of illness or inappropriate nutrition. This proposed model was justifiably criticized. Berzelius stingingly stated that "this facile kind of physiological chemistry
1456-471: A cell's size, shape, membrane potential , metabolic activity , and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics . With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. Thus, different cells can have very different physical characteristics despite having the same genome . Morphogenesis, or
1638-408: A chemical (e.g., nitrous acid , benzopyrene ) or radiation (e.g., x-ray , gamma ray , ultraviolet radiation , particles emitted by unstable isotopes). Mutations can lead to phenotypic effects such as loss-of-function, gain-of-function , and conditional mutations. Some mutations are beneficial, as they are a source of genetic variation for evolution. Others are harmful if they were to result in
1820-887: A chemical theory of metabolism. The experimental techniques used by Liebig and others often involved controlling and measuring diet, and monitoring and analyzing the products of animal metabolism, as indicators of internal metabolic processes. Liebig saw similarities between plant and animal metabolism, and suggested that nitrogenous animal matter was similar to, and derived from, plant matter. He categorized foodstuffs into two groups, nitrogenous materials which he believed were used to build animal tissue, and non-nitrogenous materials which he believed were involved in separate processes of respiration and generation of heat. French researchers such as Jean-Baptiste Dumas and Jean-Baptiste Boussingault believed that animals assimilated sugars, proteins, and fats from plant materials and that animals could not synthesize complex molecules. Liebig's work suggested
2002-419: A common ability of plants and animals to synthesize complex molecules from simpler ones. His experiments on fat metabolism convinced him that animals must be able to synthesize fats from sugars and starches. Other researchers built upon his work, confirming the abilities of animals to synthesize sugar and build fat. Liebig also studied respiration, at one point measuring the "ingesta and excreta" of 855 soldiers,
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#17328587830902184-592: A common but controversial practice at the time.) Carolina, according to Liebig, thrived on the formula. But other scientists were skeptical. One of them, a French doctor in Paris named Jean-Anne-Henri Depaul, decided to test his formula on four infants whose mothers could not suckle. Liebig himself prepared the first batches of formula. Depaul first gave it to a set of twins , who were born somewhat premature and weighed 2.24 kilograms (4.93 pounds ) and 2.64 kg (5.82 lbs.). Both died within two days. Depaul tried it on
2366-404: A design discovered independently by German chemist Christian Ehrenfried Weigel in 1771, by French scientist, P. J. Poisonnier in 1779, and by Finnish chemist Johan Gadolin in 1791. Although it was not widely adopted until after Liebig's death, when safety legislation finally prohibited the use of mercury in making mirrors , Liebig proposed a process for silvering that eventually became
2548-696: A dissertation be waived and the degree granted in absentia . Liebig left Paris to return to Darmstadt in April 1824. On 26 May 1824, at the age of 21 and with Humboldt's recommendation, Liebig became a professor extraordinarius at the University of Giessen . Liebig's appointment was part of an attempt to modernize the University of Giessen and attract more students. He received a small stipend, without laboratory funding or access to facilities. The presence of existing faculty complicated his situation: Professor Wilhelm Zimmermann (1780–1825) taught general chemistry as part of
2730-454: A double grave at Alter Friedhof cemetery in Giessen. That both died on the same day sparked the myth that they had fought against each other in a duel . However, in 2008 the local newspaper Gießener Allgemeine Zeitung , referencing a 1939 chronicle of the fraternity Corps Teutonia zu Gießen which Karl von Müller co-founded, revealed that both students had died of typhus . Von Müller had contracted
2912-1227: A few archaea have very different shapes, such as the flat and square cells of Haloquadratum walsbyi . Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation . Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes , including archaeols . Archaea use more energy sources than eukaryotes: these range from organic compounds , such as sugars, to ammonia , metal ions or even hydrogen gas . Salt-tolerant archaea (the Haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon , but unlike plants and cyanobacteria , no known species of archaea does both. Archaea reproduce asexually by binary fission , fragmentation , or budding ; unlike bacteria, no known species of Archaea form endospores . The first observed archaea were extremophiles , living in extreme environments, such as hot springs and salt lakes with no other organisms. Improved molecular detection tools led to
3094-403: A final electron acceptor, which is usually the oxidized form of NADP , which is reduced to NADPH, a process that takes place in a protein complex called photosystem I (PSI). The transport of electrons is coupled to the movement of protons (or hydrogen) from the stroma to the thylakoid membrane, which forms a pH gradient across the membrane as hydrogen becomes more concentrated in the lumen than in
3276-458: A grant obtained for him by Kastner from the Hessian government. He worked in the private laboratory of Joseph Louis Gay-Lussac and was also befriended by Alexander von Humboldt and Georges Cuvier (1769–1832). Liebig's doctorate from Erlangen was conferred on 23 June 1823, a considerable time after he left, as a result of Kastner's intervention on his behalf. Kastner pleaded that the requirement of
3458-438: A group of carbon, hydrogen, and oxygen atoms could behave like an element, take the place of an element, and can be exchanged for elements in chemical compounds . This laid the foundation for the doctrine of compound radicals , which can be seen as an early step in the development of structural chemistry. The 1830s were a period of intense investigation of organic compounds by Liebig and his students, and of vigorous debate about
3640-516: A hollow sphere of cells , the blastula , during embryonic development . Over 1.5 million living animal species have been described —of which around 1 million are insects —but it has been estimated there are over 7 million animal species in total. They have complex interactions with each other and their environments, forming intricate food webs . University of Giessen University of Giessen , official name Justus Liebig University Giessen (German: Justus-Liebig-Universität Gießen ),
3822-759: A loss of function of genes needed for survival. Gene expression is the molecular process by which a genotype encoded in DNA gives rise to an observable phenotype in the proteins of an organism's body. This process is summarized by the central dogma of molecular biology , which was formulated by Francis Crick in 1958. According to the Central Dogma, genetic information flows from DNA to RNA to protein. There are two gene expression processes: transcription (DNA to RNA) and translation (RNA to protein). The regulation of gene expression by environmental factors and during different stages of development can occur at each step of
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#17328587830904004-613: A manufacturing process for beef extracts , and with his consent a company, called Liebig Extract of Meat Company , was founded to exploit the concept; it later introduced the Oxo brand beef bouillon cube . He popularized an earlier invention for condensing vapors, which came to be known as the Liebig condenser . Justus Liebig was born in Darmstadt into the middle-class family of Johann Georg Liebig and Maria Caroline Möser in early May 1803. His father
4186-417: A more successful evolutionary theory based on natural selection ; similar reasoning and evidence led Alfred Russel Wallace to independently reach the same conclusions. The basis for modern genetics began with the work of Gregor Mendel in 1865. This outlined the principles of biological inheritance. However, the significance of his work was not realized until the early 20th century when evolution became
4368-457: A new cycle. In contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of DNA replication followed by two divisions. Homologous chromosomes are separated in the first division ( meiosis I ), and sister chromatids are separated in the second division ( meiosis II ). Both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. Both are believed to be present in
4550-471: A new era of medicine. Liebig's ideas stimulated medical research, led to the development of better techniques for testing experimental models of metabolism, and pointed to chemistry as fundamental to the understanding of health and disease. In 1850, Liebig investigated spontaneous human combustion , dismissing the simplistic explanations based on ethanol due to alcoholism. Liebig drew upon his work in plant nutrition and plant and animal metabolism to develop
4732-740: A number of persons as possible by the extension of the manufacture, and consequently a reduction in the cost". Production was not economically feasible in Europe, where meat was expensive, but in Uruguay and New South Wales , meat was an inexpensive byproduct of the leather industry. In 1865, Liebig partnered with Belgian engineer George Christian Giebert , and was named scientific director of Liebig's Extract of Meat Company , located in Fray Bentos in Uruguay. Other companies also attempted to market meat extracts under
4914-409: A process known as allopatric speciation . A phylogeny is an evolutionary history of a specific group of organisms or their genes. It can be represented using a phylogenetic tree , a diagram showing lines of descent among organisms or their genes. Each line drawn on the time axis of a tree represents a lineage of descendants of a particular species or population. When a lineage divides into two, it
5096-408: A region of deoxyribonucleic acid (DNA) that carries genetic information that controls form or function of an organism. DNA is composed of two polynucleotide chains that coil around each other to form a double helix . It is found as linear chromosomes in eukaryotes , and circular chromosomes in prokaryotes . The set of chromosomes in a cell is collectively known as its genome . In eukaryotes, DNA
5278-541: A role in the synthesis and packaging of proteins, respectively. Biomolecules such as proteins can be engulfed by lysosomes , another specialized organelle. Plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. Eukaryotic cells also have cytoskeleton that
5460-436: A separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. Like groupings such as algae , invertebrates , or protozoans , the protist grouping is not a formal taxonomic group but is used for convenience. Most protists are unicellular; these are called microbial eukaryotes. Plants are mainly multicellular organisms , predominantly photosynthetic eukaryotes of
5642-539: A short time and the impact of his own work. At a time when many chemists such as Jöns Jakob Berzelius still insisted on a hard and fast separation between the organic and inorganic, Liebig asserted: "The production of all organic substances no longer belongs just to living organisms. It must be seen as not only probable, but as certain, that we shall be able to produce them in our laboratories. Sugar, salicin, and morphine will be artificially produced. Of course, we do not yet know how to do this, because we do not yet know
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5824-423: A single carbon atom can form four single covalent bonds such as in methane , two double covalent bonds such as in carbon dioxide (CO 2 ), or a triple covalent bond such as in carbon monoxide (CO). Moreover, carbon can form very long chains of interconnecting carbon–carbon bonds such as octane or ring-like structures such as glucose . The simplest form of an organic molecule is the hydrocarbon , which
6006-558: A single, coherent field. For instance, all organisms are made up of at least one cell that processes hereditary information encoded in genes , which can be transmitted to future generations. Another major theme is evolution , which explains the unity and diversity of life. Energy processing is also important to life as it allows organisms to move , grow, and reproduce . Finally, all organisms are able to regulate their own internal environments . Biologists are able to study life at multiple levels of organization , from
6188-446: A specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts —they allow a reaction to proceed more rapidly without being consumed by it—by reducing the amount of activation energy needed to convert reactants into products . Enzymes also allow
6370-489: A theory of nutrition, which had implications for cookery. In his Researches on the Chemistry of Food (1847) Liebig argued that eating not only meat fibre, but also meat juices, which contained various inorganic chemicals, was important. These vital ingredients would be lost during conventional boiling or roasting in which cooking liquids were discarded. For optimum nutritional quality, Liebig advised that cooks should either sear
6552-449: A third baby, born full-term at 3.37 kg (7.43 lbs.); it soon began passing green " starvation stools " and died within three days. A fourth child, weighing 2.76 kg, also developed green stools and died within four days. At this point, Depaul stopped the experiment. Biology Biology is the scientific study of life . It is a natural science with a broad scope but has several unifying themes that tie it together as
6734-420: A time. He lived in a cramped apartment with his wife and children on the floor above. Liebig was one of the first chemists to organize a laboratory in its present form, engaging with students in empirical research on a large scale through a combination of research and teaching. His methods of organic analysis enabled him to direct the analytical work of many graduate students. Liebig's students were from many of
6916-399: A unified theory as the modern synthesis reconciled Darwinian evolution with classical genetics . In the 1940s and early 1950s, a series of experiments by Alfred Hershey and Martha Chase pointed to DNA as the component of chromosomes that held the trait-carrying units that had become known as genes . A focus on new kinds of model organisms such as viruses and bacteria, along with
7098-421: A varied mix of traits, and reproduction is able to increase any population, Darwin argued that in the natural world, it was nature that played the role of humans in selecting for specific traits. Darwin inferred that individuals who possessed heritable traits better adapted to their environments are more likely to survive and produce more offspring than other individuals. He further inferred that this would lead to
7280-492: A water molecule again. In pure water , the number of hydrogen ions balances (or equals) the number of hydroxyl ions, resulting in a pH that is neutral. Organic compounds are molecules that contain carbon bonded to another element such as hydrogen. With the exception of water, nearly all the molecules that make up each organism contain carbon. Carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. For example,
7462-444: Is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. Two aspects of sexual reproduction , meiotic recombination and outcrossing , are likely maintained respectively by the adaptive advantages of recombinational repair of genomic DNA damage and genetic complementation which masks
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7644-641: Is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. A hydrocarbon backbone can be substituted by other elements such as oxygen (O), hydrogen (H), phosphorus (P), and sulfur (S), which can change the chemical behavior of that compound. Groups of atoms that contain these elements (O-, H-, P-, and S-) and are bonded to a central carbon atom or skeleton are called functional groups . There are six prominent functional groups that can be found in organisms: amino group , carboxyl group , carbonyl group , hydroxyl group , phosphate group , and sulfhydryl group . In 1953,
7826-650: Is a large public research university in Giessen , Hesse , Germany . It is one of the oldest institutions of higher education in the German-speaking world . It is named after its most famous faculty member, Justus von Liebig , the founder of modern agricultural chemistry and inventor of artificial fertiliser. It covers the areas of arts/humanities, business, dentistry, economics, law, medicine, science, social sciences and veterinary medicine. Its university hospital , which has two sites, Giessen and Marburg (the latter of which
8008-564: Is a qualitative version of the principles used for determining the application of fertilizer in modern agriculture. Organic Chemistry was not intended as a guide to practical agriculture. Liebig's lack of experience in practical applications, and differences between editions of the book, fueled considerable criticism. Nonetheless, Liebig's writings had a profound impact on agriculture, spurring experiment and theoretical debate in Germany, England, and France. One of his most recognized accomplishments
8190-480: Is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen (H) atoms to one oxygen (O) atom (H 2 O). Because the O–H bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. This polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive . Surface tension results from
8372-918: Is a term of convenience as not all algae are closely related. Algae comprise several distinct clades such as glaucophytes , which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of Plantae. Unlike glaucophytes, the other algal clades such as red and green algae are multicellular. Green algae comprise three major clades: chlorophytes , coleochaetophytes , and stoneworts . Fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. Many fungi are also saprobes , feeding on dead organic matter, making them important decomposers in ecological systems. Animals are multicellular eukaryotes. With few exceptions, animals consume organic material , breathe oxygen , are able to move , can reproduce sexually , and grow from
8554-403: Is catalyzed by lactate dehydrogenase in a reversible reaction. Lactate can also be used as an indirect precursor for liver glycogen. During recovery, when oxygen becomes available, NAD attaches to hydrogen from lactate to form ATP. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation . The ATP generated in this process
8736-507: Is created at the writing table". Some of the ideas that Liebig had enthusiastically incorporated were not supported by further research. The third and last edition of Animal Chemistry (1846) was substantially revised and did not include the equations. The third area discussed in Animal Chemistry was fermentation and putrefaction. Liebig proposed chemical explanations for processes such as eremacausis (organic decomposition), describing
8918-441: Is made by substrate-level phosphorylation , which does not require oxygen. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism's metabolic activities via cellular respiration. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. In most cases, oxygen
9100-535: Is made up of microtubules , intermediate filaments , and microfilaments , all of which provide support for the cell and are involved in the movement of the cell and its organelles. In terms of their structural composition, the microtubules are made up of tubulin (e.g., α-tubulin and β-tubulin ) whereas intermediate filaments are made up of fibrous proteins. Microfilaments are made up of actin molecules that interact with other strands of proteins. All cells require energy to sustain cellular processes. Metabolism
9282-526: Is mainly in the cell nucleus . In prokaryotes, the DNA is held within the nucleoid . The genetic information is held within genes, and the complete assemblage in an organism is called its genotype . DNA replication is a semiconservative process whereby each strand serves as a template for a new strand of DNA. Mutations are heritable changes in DNA. They can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as
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#17328587830909464-399: Is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction , it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. Sugar in
9646-407: Is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. Growth of a new cell wall begins to separate the bacterium (triggered by FtsZ polymerization and "Z-ring" formation). The new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. The new daughter cells have tightly coiled DNA rods, ribosomes , and plasmids . Meiosis
9828-419: Is regarded as one of the most outstanding chemistry teachers of all time. He has been described as the "father of the fertilizer industry" for his emphasis on nitrogen and minerals as essential plant nutrients , and his popularization of the law of the minimum , which states that plant growth is limited by the scarcest nutrient resource, rather than the total amount of resources available. He also developed
10010-399: Is released as a waste product. Most plants, algae , and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth. Photosynthesis has four stages: Light absorption , electron transport, ATP synthesis, and carbon fixation . Light absorption is
10192-412: Is represented as a fork or split on the phylogenetic tree. Phylogenetic trees are the basis for comparing and grouping different species. Different species that share a feature inherited from a common ancestor are described as having homologous features (or synapomorphy ). Phylogeny provides the basis of biological classification. This classification system is rank-based, with the highest rank being
10374-486: Is the development of nitrogen -based fertilizer . In the first two editions of his book (1840, 1842), Liebig reported that the atmosphere contained insufficient nitrogen, and argued that nitrogen-based fertilizer was needed to grow the healthiest possible crops. Liebig believed that nitrogen could be supplied in the form of ammonia , and recognized the possibility of substituting chemical fertilizers for natural ones (animal dung, etc.) He later became convinced that nitrogen
10556-468: Is the process by which genes and traits are passed on from parents to offspring. It has several principles. The first is that genetic characteristics, alleles , are discrete and have alternate forms (e.g., purple vs. white or tall vs. dwarf), each inherited from one of two parents. Based on the law of dominance and uniformity , which states that some alleles are dominant while others are recessive ; an organism with at least one dominant allele will display
10738-485: Is the set of chemical reactions in an organism. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to monomer building blocks; and the elimination of metabolic wastes . These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolic reactions may be categorized as catabolic —the breaking down of compounds (for example,
10920-410: Is the study of chemical processes within and relating to living organisms . Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. Life arose from the Earth's first ocean, which formed some 3.8 billion years ago. Since then, water continues to be
11102-734: Is the teaching hospital of the University of Marburg ), is the only private university hospital in Germany. The University of Giessen is among the oldest institutions of higher educations in the German-speaking world. It was founded in 1607 as a Lutheran university in the city of Giessen in Hesse-Darmstadt because the all-Hessian Landesuniversität (the nearby University of Marburg ( Philipps-Universität Marburg ) in Marburg , Hesse-Kassel (or Hesse-Cassel)) had become Reformed (that is, Calvinist ). Louis V, Landgrave of Hesse-Darmstadt , whence
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#173285878309011284-493: Is to store, transmit, and express hereditary information. Cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division . Most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope . There are generally two types of cells: eukaryotic cells, which contain
11466-629: The Cambrian explosion . During the Permian period, synapsids , including the ancestors of mammals , dominated the land, but most of this group became extinct in the Permian–Triassic extinction event 252 million years ago. During the recovery from this catastrophe, archosaurs became the most abundant land vertebrates; one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods. After
11648-495: The Cretaceous–Paleogene extinction event 66 million years ago killed off the non-avian dinosaurs, mammals increased rapidly in size and diversity . Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. Bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms . Typically a few micrometers in length, bacteria have
11830-535: The Miller–Urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early Earth , thus suggesting that complex organic molecules could have arisen spontaneously in early Earth (see abiogenesis ). Macromolecules are large molecules made up of smaller subunits or monomers . Monomers include sugars, amino acids, and nucleotides. Carbohydrates include monomers and polymers of sugars. Lipids are
12012-492: The Precambrian about 1.5 billion years ago and can be classified into eight major clades : alveolates , excavates , stramenopiles , plants, rhizarians , amoebozoans , fungi , and animals. Five of these clades are collectively known as protists , which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor ), protists by themselves do not constitute
12194-513: The University of Erlangen , Liebig followed him. Liebig left Erlangen in March 1822, in part because of his involvement with the radical Korps Rhenania (a nationalist student organization), but also because of his hopes for more advanced chemical studies. The circumstances are clouded by possible scandal. Some scholars argue that he fled to Paris because of his involvement in radical student groups. In late October 1822, Liebig went to Paris to study on
12376-727: The activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. Negative regulation occurs when another transcription factor called a repressor binds to a DNA sequence called an operator , which is part of an operon, to prevent transcription. Repressors can be inhibited by compounds called inducers (e.g., allolactose ), thereby allowing transcription to occur. Specific genes that can be activated by inducers are called inducible genes , in contrast to constitutive genes that are almost constantly active. In contrast to both, structural genes encode proteins that are not involved in gene regulation. In addition to regulatory events involving
12558-585: The bacterial phyla have species that can be grown in the laboratory. Archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom ), a term that has fallen out of use. Archaeal cells have unique properties separating them from the other two domains , Bacteria and Eukaryota . Archaea are further divided into multiple recognized phyla . Archaea and bacteria are generally similar in size and shape, although
12740-404: The cell . In 1838, Schleiden and Schwann began promoting the now universal ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics of life, although they opposed the idea that (3) all cells come from the division of other cells, continuing to support spontaneous generation . However, Robert Remak and Rudolf Virchow were able to reify
12922-403: The cell membrane of another cell or located deep inside a cell. There are generally four types of chemical signals: autocrine , paracrine , juxtacrine , and hormones . In autocrine signaling, the ligand affects the same cell that releases it. Tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self-division. In paracrine signaling,
13104-416: The circulatory systems of animals or vascular systems of plants to reach their target cells. Once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. For instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. Other types of receptors include protein kinase receptors (e.g., receptor for
13286-461: The cycling of nutrients and energy through their biophysical environment . The earliest of roots of science, which included medicine, can be traced to ancient Egypt and Mesopotamia in around 3000 to 1200 BCE . Their contributions shaped ancient Greek natural philosophy . Ancient Greek philosophers such as Aristotle (384–322 BCE) contributed extensively to the development of biological knowledge. He explored biological causation and
13468-528: The domain followed by kingdom , phylum , class , order , family , genus , and species . All organisms can be classified as belonging to one of three domains : Archaea (originally Archaebacteria), bacteria (originally eubacteria), or eukarya (includes the fungi, plant, and animal kingdoms). The history of life on Earth traces how organisms have evolved from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and all life on Earth, both living and extinct, descended from
13650-481: The duplication of its DNA and some of its organelles , and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division . In eukaryotes (i.e., animal, plant, fungal , and protist cells), there are two distinct types of cell division: mitosis and meiosis . Mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which
13832-403: The kingdom Plantae, which would exclude fungi and some algae . Plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. The first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which
14014-423: The microscope . It was then that scholars discovered spermatozoa , bacteria, infusoria and the diversity of microscopic life. Investigations by Jan Swammerdam led to new interest in entomology and helped to develop techniques of microscopic dissection and staining . Advances in microscopy had a profound impact on biological thinking. In the early 19th century, biologists pointed to the central importance of
14196-412: The mitochondrial cristae . Oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from NADH and FADH 2 that is coupled to the pumping of protons (hydrogen ions) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force . Energy from
14378-445: The molecular biology of a cell to the anatomy and physiology of plants and animals, and evolution of populations. Hence, there are multiple subdisciplines within biology , each defined by the nature of their research questions and the tools that they use. Like other scientists, biologists use the scientific method to make observations , pose questions, generate hypotheses , perform experiments, and form conclusions about
14560-546: The phenotype of that dominant allele. During gamete formation, the alleles for each gene segregate, so that each gamete carries only one allele for each gene. Heterozygotic individuals produce gametes with an equal frequency of two alleles. Finally, the law of independent assortment , states that genes of different traits can segregate independently during the formation of gametes, i.e., genes are unlinked. An exception to this rule would include traits that are sex-linked . Test crosses can be performed to experimentally determine
14742-497: The regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells. Cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions , which break large molecules into smaller ones, releasing energy. Respiration
14924-567: The " Oxo " trademark. Oxo was trademarked worldwide in 1899 and in the United Kingdom in 1900. Originally a liquid, Oxo was released in cubed solid form in 1911. Liebig studied other foods, as well. He promoted the use of baking powder to make lighter bread, studied the chemistry of coffee-making and oatmeal . He is considered to have made possible the invention of Marmite , because of his discovery that yeast could be concentrated to form yeast extract . Infant Formula Liebig produced some of
15106-525: The Faculty of Economics, new practical subjects were brought together ( veterinary medicine , forestry , and cameral sciences ), which the university was supposed to make "expedient" and "profitable". (One of the earliest courses of study in forestry in Europe.) After finishing studies in this Faculty, a number of these youths were able to gain recognition in the Faculties of Medicine and Philosophy. They established
15288-555: The German states, as well as Britain and the United States. They helped create an international reputation for their Doktorvater. His laboratory became renowned as a model institution for the teaching of practical chemistry. It was also significant for its emphasis on applying discoveries in fundamental research to the development of specific chemical processes and products. In 1833, Liebig convinced chancellor Justin von Linde to include
15470-475: The Phanerozoic eon that began 539 million years ago being subdivided into Paleozoic , Mesozoic , and Cenozoic eras. These three eras together comprise eleven periods ( Cambrian , Ordovician , Silurian , Devonian , Carboniferous , Permian , Triassic , Jurassic , Cretaceous , Tertiary , and Quaternary ). The similarities among all known present-day species indicate that they have diverged through
15652-519: The Rutherford atomic model 's creator, studied in Giessen. Alumnus William Schlich founded Oxford University 's forestry program. Ruth Kajander was a psychiatrist who pioneered use of chlorpromazine as a treatment for schizophrenia. Carl A. Schenck , who received his PhD in forestry from Giessen, founded the Biltmore Forest School , the first such school in the United States. Fitsum Assefa
15834-690: The Veterinary Faculty. Recent alumni in the area of politics include current President of Germany and former Vice Chancellor and Minister for Foreign Affairs Frank-Walter Steinmeier and Brigitte Zypries , current Federal Minister of Economic Affairs and Energy and former Federal Minister of Justice. Notable alumni of the university include organic chemist August Kekulé , X-ray physicist Simone Techert , health sociologist Thomas Abel , romantic dramatist and revolutionary Georg Büchner , literary and political historian Georg Gottfried Gervinus and botanist Johann Jacob Dillenius . Ernest Rutherford ,
16016-696: The accumulation of favorable traits over successive generations, thereby increasing the match between the organisms and their environment. A species is a group of organisms that mate with one another and speciation is the process by which one lineage splits into two lineages as a result of having evolved independently from each other. For speciation to occur, there has to be reproductive isolation . Reproductive isolation can result from incompatibilities between genes as described by Bateson–Dobzhansky–Muller model . Reproductive isolation also tends to increase with genetic divergence . Speciation can occur when there are physical barriers that divide an ancestral species,
16198-463: The basis of modern mirror-making. In 1835, he reported that aldehydes reduce silver salts to metallic silver. After working with other scientists, Carl August von Steinheil approached Liebig in 1856 to see if he could develop a silvering technique capable of producing high-quality optical mirrors for use in reflecting telescopes . Liebig developed blemish-free mirrors by adding copper to ammoniated silver nitrate and sugar. An attempt to commercialize
16380-541: The biological N fixation. [1] Nitrogen fertilizers are now widely used throughout the world, and their production is a substantial segment of the chemical industry. Liebig's work on applying chemistry to plant and animal physiology was especially influential. By 1842, he had published Chimie organique appliquée à la physiologie animale et à la pathologie , published in English as Animal Chemistry, or, Organic Chemistry in its Applications to Physiology and Pathology , presenting
16562-586: The body plan and the number, identity, and pattern of body parts. Among the most important toolkit genes are the Hox genes . Hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. Evolution is a central organizing concept in biology. It is the change in heritable characteristics of populations over successive generations . In artificial selection , animals were selectively bred for specific traits. Given that traits are inherited, populations contain
16744-450: The breaking down of glucose to pyruvate by cellular respiration ); or anabolic —the building up ( synthesis ) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy. The chemical reactions of metabolism are organized into metabolic pathways , in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by
16926-410: The cohesive force due to the attraction between molecules at the surface of the liquid. Water is also adhesive as it is able to adhere to the surface of any polar or charged non-water molecules. Water is denser as a liquid than it is as a solid (or ice). This unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from
17108-433: The cold air above. Water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol . Thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor . As a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into
17290-428: The company emphasized its convenience and flavor, marketing it as a comfort food. The Liebig company worked with popular cookery writers in various countries to popularize their products. German cookery writer Henriette Davidis wrote recipes for Improved and Economic Cookery and other cookbooks. Katharina Prato wrote an Austro-Hungarian recipe book, Die Praktische Verwerthung Kochrecepte (1879). Hannah M. Young
17472-501: The cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids . In addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. These organelles include the cell nucleus , which contains most of the cell's DNA, or mitochondria , which generate adenosine triphosphate (ATP) to power cellular processes. Other organelles such as endoplasmic reticulum and Golgi apparatus play
17654-455: The cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. Fermentation oxidizes NADH to NAD so it can be re-used in glycolysis. In the absence of oxygen, fermentation prevents the buildup of NADH in the cytoplasm and provides NAD for glycolysis. This waste product varies depending on
17836-418: The development of body form, is the result of spatial differences in gene expression. A small fraction of the genes in an organism's genome called the developmental-genetic toolkit control the development of that organism. These toolkit genes are highly conserved among phyla , meaning that they are ancient and very similar in widely separated groups of animals. Differences in deployment of toolkit genes affect
18018-440: The developmental fate of a cell, which becomes more restrictive during development. Differentiation is the process by which specialized cells arise from less specialized cells such as stem cells . Stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. Cellular differentiation dramatically changes
18200-411: The discovery of archaea in almost every habitat , including soil, oceans, and marshlands . Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life . They are part of the microbiota of all organisms. In the human microbiome , they are important in the gut , mouth, and on
18382-420: The discovery of the double-helical structure of DNA by James Watson and Francis Crick in 1953, marked the transition to the era of molecular genetics . From the 1950s onwards, biology has been vastly extended in the molecular domain. The genetic code was cracked by Har Gobind Khorana , Robert W. Holley and Marshall Warren Nirenberg after DNA was understood to contain codons . The Human Genome Project
18564-542: The disease while nursing his sick friend. The Corps buried both students after a torch-lit funeral procession. According to the 2024 QS World University Rankings , the university was placed 396th globally and 22nd nationally. In the Times Higher Education (THE) World University Rankings for 2023, it fell within the 351–400 bracket internationally and ranked between 34th and 36th at the national level. The 2023 Academic Ranking of World Universities (ARWU) placed
18746-594: The diversity of life. His successor, Theophrastus , began the scientific study of plants. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz (781–869), Al-Dīnawarī (828–896), who wrote on botany, and Rhazes (865–925) who wrote on anatomy and physiology . Medicine was especially well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew heavily on Aristotelian thought. Biology began to quickly develop with Anton van Leeuwenhoek 's dramatic improvement of
18928-616: The earliest terrestrial ecosystems , at least 2.7 billion years ago. Microorganisms are thought to have paved the way for the inception of land plants in the Ordovician period. Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event . Ediacara biota appear during the Ediacaran period, while vertebrates , along with most other modern phyla originated about 525 million years ago during
19110-422: The edition accordingly. Liebig's idea that " searing meat seals in the juices", though still widely believed, is not true. Building on his theories of the nutritional value of meat fluids, and seeking an inexpensive nutrition source for Europe's poor, Liebig developed a formula for producing beef extract. The details were published in 1847 so that "the benefit of it should ... be placed at the command of as large
19292-473: The expression of deleterious recessive mutations . The beneficial effect of genetic complementation, derived from outcrossing (cross-fertilization) is also referred to as hybrid vigor or heterosis. Charles Darwin in his 1878 book The Effects of Cross and Self-Fertilization in the Vegetable Kingdom at the start of chapter XII noted “The first and most important of the conclusions which may be drawn from
19474-460: The first time included in the student body were women, who since 1900 were admitted as guest students and starting in 1908 were admitted for regular study. After the different Hessian states were (re-)united in 1929, both universities became public universities of that German state. The University of Giessen now has almost 23,000 students and 8,500 employees, which together with the Giessen students of Technische Hochschule Mittelhessen , makes Giessen
19656-402: The first time. In the years 2019 to 2021 the student number was about 28,300, with a decrease to 27,400 students in the winter term 2021/2022 (probably due to COVID restrictions). Although the university has no defined campus, buildings and facilities are grouped together according to their subject areas and situated in various locations around Giessen. Philosophikum II, for example is an area on
19838-455: The form of glucose is the main nutrient used by animal and plant cells in respiration. Cellular respiration involving oxygen is called aerobic respiration, which has four stages: glycolysis , citric acid cycle (or Krebs cycle), electron transport chain , and oxidative phosphorylation . Glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates , with two net molecules of ATP being produced at
20020-454: The four common faculties (theology, law, medicine, and philosophy). The instruction was reasonable, with about 20 to 25 professors teaching several hundred students, the latter of which were mostly "Landeskinder". In the 18th century came gradual modernization of the curricula and reforms in the instruction, which were definitively influenced by the local lordly court in Darmstadt. The example for
20202-521: The global famine that ensued, and the experience is said to have shaped Liebig's later work. Due in part to Liebig's innovations in fertilizers and agriculture, the 1816 famine became known as "the last great subsistence crisis in the Western world". Liebig attended grammar school at the Ludwig-Georgs-Gymnasium in Darmstadt, from the ages of 8 to 14. Leaving without a certificate of completion, he
20384-426: The hormone insulin ) and G protein-coupled receptors . Activation of G protein-coupled receptors can initiate second messenger cascades. The process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction . The cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. These events include
20566-576: The idea of isomers , substances that are defined not simply by the number and kind of atoms in the molecule, but also by the arrangement of those atoms. In 1832, Liebig and Friedrich Wöhler published an investigation of the oil of bitter almonds. They transformed pure oil into several halogenated compounds, which were further transformed in other reactions. Throughout these transformations, "a single compound" (which they named benzoyl ) "preserves its nature and composition unchanged in nearly all its associations with other bodies." Their experiments proved that
20748-582: The idea that chemistry could revolutionize agricultural practice, increasing yields and lowering costs. It was widely translated, vociferously critiqued, and highly influential. Liebig's book discussed chemical transformations within living systems, both plant and animal, outlining a theoretical approach to agricultural chemistry. The book's first part focused on plant nutrition; the second was on chemical mechanisms of putrefaction and decay. Liebig's awareness of both synthesis and degradation led him to become an early advocate of conservation , promoting ideas such as
20930-599: The importance of De Saussures' findings, and used them to critique humus theories, while regretting the limitations of De Saussure's experimental techniques. Using more precise methods of measurement as a basis for estimation, he pointed out contradictions such as the inability of existing soil humus to provide enough carbon to support the plants growing in it. By the late 1830s, researchers such as Karl Sprengel were using Liebig's methods of combustion analysis to assess manures, concluding that their value could be attributed to their constituent minerals. Liebig synthesized ideas about
21112-418: The importance of minerals in the soil, he argued that plants feed on nitrogen compounds derived from the air. This assertion was a source of contention for many years, and turned out to be true for legumes, but not for other plants. Liebig also popularized Carl Sprengel's "theorem of minimum" (known as the law of the minimum ), stating that plant growth is not determined by the total resources available, but by
21294-414: The initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes . The absorbed light energy is used to remove electrons from a donor (water) to a primary electron acceptor, a quinone designated as Q. In the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach
21476-452: The institute within the university. In 1839, he obtained government funds to build a lecture theatre and two separate laboratories designed by architect Paul Hofmann . The new chemistry laboratory featured innovative glass-fronted fume cupboards and venting chimneys. By 1852, when he left Giessen for Munich, more than 700 students of chemistry and pharmacy had studied with Liebig. A significant challenge facing 19th-century organic chemists
21658-417: The institution in the 601–700 range globally, and between 37th and 40th nationally. Next to Liebig, famous professors at the university included the physician Georg Haas (who carried out the world's first human hemodialysis in Giessen in 1924), the theologian Adolf von Harnack , the lawyer Rudolf von Jhering , the economist and statistician Etienne Laspeyres , the physicist Wilhelm Conrad Röntgen ,
21840-406: The last eukaryotic common ancestor. Prokaryotes (i.e., archaea and bacteria) can also undergo cell division (or binary fission ). Unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. Before binary fission, DNA in the bacterium is tightly coiled. After it has uncoiled and duplicated, it
22022-459: The lawyer Rudolf von Jhering , the theologian Adolf von Harnack , the mathematician Moritz Pasch and the physicist Wilhelm Conrad Röntgen . At the turn of the 20th century, the Ludoviciana began to expand into a modern university. During this period, new clinics in human and veterinary medicine were established, and the university library received its first proper building. With the creation of
22204-405: The ligand diffuses to nearby cells and affects them. For example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell . In juxtacrine signaling, there is direct contact between the signaling and responding cells. Finally, hormones are ligands that travel through
22386-472: The mathematicians Moritz Pasch and Alfred Clebsch , the gestalt psychologist Kurt Koffka , the philologist and archaeologist Friedrich Gottlieb Welcker , the orientalists Friedrich Schwally , Paul E. Kahle and Eberhard Schrader , and the president of Hebrew University of Jerusalem Benjamin Mazar . From 1901 to 1918 Hermann Friedrich Gmeiner was the first Professor for veterinary internal medicine at
22568-480: The meat initially to retain fluids, or retain and use cooking liquids (as in soups or stews). Liebig was acclaimed in The Lancet for revealing "the true principles of cookery", and physicians promoted "rational diets" based on his ideas. Well-known British cookery writer Eliza Acton responded to Liebig by modifying the cookery techniques in the third edition of her Modern Cookery for Private Families , and subtitling
22750-444: The membrane serving as membrane transporters , and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. Cell membranes are involved in various cellular processes such as cell adhesion , storing electrical energy , and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall , glycocalyx , and cytoskeleton . Within
22932-461: The method's accuracy of measurement. Liebig's assistant, Carl Ettling, perfected glass-blowing techniques for producing the Kaliapparat and demonstrated them to visitors. Liebig's kaliapparat simplified the method of quantitative organic analysis and rendered it routine. Brock suggests that the availability of a superior technical apparatus was one reason why Liebig was able to attract so many students to his laboratory. His method of combustion analysis
23114-442: The mineral theory of plant nutrition and added his own conviction that inorganic materials could provide nutrients as effectively as organic sources. In his theory of mineral nutrients, Liebig identified the chemical elements of nitrogen (N), phosphorus (P), and potassium (K) as essential to plant growth. He reported that plants acquire carbon (C) and hydrogen (H) from the atmosphere and from water (H 2 O). In addition to emphasizing
23296-403: The mitotic phase of an animal cell cycle—the division of the mother cell into two genetically identical daughter cells. The cell cycle is a vital process by which a single-celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells , and some internal organs are renewed. After cell division, each of the daughter cells begin the interphase of
23478-437: The most abundant molecule in every organism. Water is important to life because it is an effective solvent , capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution . Once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. In terms of its molecular structure , water
23660-462: The most student-dominated German city. In December 2019 the university shut down all of its IT-servers after a "serious IT security incident". Hess State Prosecution Office investigated the case of a suspected hacker-attack. Following is the growth in the student population of University of Giessen In the 2014/2015 winter semester the student population exceeded the mark of more than a total of 28,000 students and 7,000 first-semester students for
23842-439: The name "Liebig's Extract of Meat". In Britain, a competitor's right to use the name was successfully defended on the grounds that the name had fallen into general use and become a generic term before the creation of any particular company. The judge asserted that "Purchasers must use their eyes", and considered the presentation of the products to be sufficiently different to enable the discriminating consumer to determine which of
24024-446: The nitrogen content of bases; the study of chlorination and the isolation of chloral (1832); the identification of the ethyl radical (1834); the oxidation of alcohol and formation of aldehyde (1835); the polybasic theory of organic acids (1838); and the degradation of urea (1837). Writing about the analysis of urine, a complex organic product, he made a declaration that reveals both the changes that were occurring in chemistry over
24206-441: The observations given in this volume, is that generally cross-fertilisation is beneficial and self-fertilisation often injurious, at least with the plants on which I experimented.” Genetic variation , often produced as a byproduct of sexual reproduction, may provide long-term advantages to those sexual lineages that engage in outcrossing . Genetics is the scientific study of inheritance. Mendelian inheritance , specifically,
24388-517: The only class of macromolecules that are not made up of polymers. They include steroids , phospholipids , and fats, largely nonpolar and hydrophobic (water-repelling) substances. Proteins are the most diverse of the macromolecules. They include enzymes , transport proteins , large signaling molecules, antibodies , and structural proteins . The basic unit (or monomer) of a protein is an amino acid . Twenty amino acids are used in proteins. Nucleic acids are polymers of nucleotides . Their function
24570-404: The organism. In skeletal muscles, the waste product is lactic acid . This type of fermentation is called lactic acid fermentation . In strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by NADH. During anaerobic glycolysis, NAD regenerates when pairs of hydrogen combine with pyruvate to form lactate. Lactate formation
24752-436: The outskirts of the city bordering the city forest. A number of faculty buildings and lecture theaters are located there, including Audimax, a building containing several lecture halls whose atrium is often the venue for concerts and disco nights, locally known as "Uni-Party". Two law students of University of Giessen, Karl Siegfrieden (4 June 1822 – 10 March 1840) and Karl von Müller (10 June 1799 – 10 March 1840), are buried in
24934-587: The philosophy faculty, leaving medical chemistry and pharmacy to Professor Philipp Vogt in the medical faculty. Vogt was happy to support a reorganization in which pharmacy was taught by Liebig and became the responsibility of the faculty of arts, rather than the faculty of medicine. Zimmermann found himself competing unsuccessfully with Liebig for students and their lecture fees. He refused to allow Liebig to use existing space and equipment and finally committed suicide on 19 July 1825. The deaths of Zimmermann and Professor Blumhof, who taught technology and mining, opened
25116-428: The possibility of common descent . Serious evolutionary thinking originated with the works of Jean-Baptiste Lamarck , who presented a coherent theory of evolution. The British naturalist Charles Darwin , combining the biogeographical approach of Humboldt , the uniformitarian geology of Lyell , Malthus's writings on population growth, and his own morphological expertise and extensive natural observations, forged
25298-404: The precursors from which these compounds arise, but we shall come to know them." Liebig's arguments against any chemical distinction between living (physiological) and dead chemical processes proved a great inspiration to several of his students and others who were interested in materialism . Though Liebig distanced himself from the direct political implications of materialism, he tacitly supported
25480-451: The process and "drive out mercury mirror-making and its injurious influence on workers' health" was unsuccessful. Liebig's mirrors struggled commercially due to poor glass, which produced an off-color, greenish-yellow reflection. Rudely, Liebig commented that Frenchwomen especially hated his mirrors because Frenchwomen already looked yellow and sickly, and the mirrors just reminded them how ugly they were. One of Liebig's frequent collaborators
25662-907: The process of evolution from their common ancestor. Biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria , archaea , and eukaryotes . Microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean eon and many of the major steps in early evolution are thought to have taken place in this environment. The earliest evidence of eukaryotes dates from 1.85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism . Later, around 1.7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. Algae-like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed
25844-539: The process such as transcription , RNA splicing , translation , and post-translational modification of a protein. Gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the DNA sequence close to or at a promoter. A cluster of genes that share the same promoter is called an operon , found mainly in prokaryotes and some lower eukaryotes (e.g., Caenorhabditis elegans ). In positive regulation of gene expression,
26026-456: The products bore Liebig's signature and was supported by Liebig himself. Liebig's company initially promoted their "meat tea" for its curative powers and nutritional value as a cheap, nutritious alternative to real meat. But such claims did not hold up to scrutiny. In 1868 the German physiologist Edward Kemmerich ran an experiment involving feeding the extract to dogs, every one of which died. After claims of its nutritional value were questioned,
26208-517: The promoter, gene expression can also be regulated by epigenetic changes to chromatin , which is a complex of DNA and protein found in eukaryotic cells. Development is the process by which a multicellular organism (plant or animal) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. There are four key processes that underlie development: Determination , differentiation , morphogenesis , and growth. Determination sets
26390-406: The proton motive force drives the enzyme ATP synthase to synthesize more ATPs by phosphorylating ADPs . The transfer of electrons terminates with molecular oxygen being the final electron acceptor . If oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation . The pyruvate is not transported into the mitochondrion but remains in
26572-518: The real world of agriculture was more complex than was at first realized. By the publication of the seventh German edition of Agricultural Chemistry he had moderated some of his views, admitting some mistakes and returning to the position that nitrogen-based fertilizers were beneficial or even necessary.He was instrumental in the use of guano for nitrogen. In 1863 he published the book "Es ist ja die Spitze meines lebens" in which he revised his early perceptions, now appreciating soil life and in particular
26754-530: The rearrangement of atoms as a result of unstable "affinities" reacting to external causes such as air or already decaying substances. Liebig identified the blood as the site of the body's "chemical factory", where he believed processes of synthesis and degradation took place. He presented a view of disease in terms of chemical process, in which healthy blood could be attacked by external contagia; secreting organs sought to transform and excrete such substances; and failure to do so could lead to their elimination through
26936-625: The recycling of sewage . Liebig argued against prevalent theories about role of humus in plant nutrition, which held that decayed plant matter was the primary source of carbon for plant nutrition. Fertilizers were believed to act by breaking down humus, making it easier for plants to absorb. Associated with such ideas was the belief that some sort of "vital force" distinguished reactions involving organic as opposed to inorganic materials. Early studies of photosynthesis had identified carbon, hydrogen, oxygen, and nitrogen as important, but disagreed over their sources and mechanisms of action. Carbon dioxide
27118-508: The reforms were both of the "model universities of the Enlightenment", the University of Halle, founded in 1694, and more still Georgia Augusta, founded in Göttingen in 1734/37. Indeed, all attempts at reform were from the start limited by the limited finances of Hesse-Darmstadt. The noteworthy creation of a Faculty of Economics (1777–1785) was ultimately born out of this financial hardship. In
27300-505: The revolutionary spirit of this decade. With the appointment of the 21-year-old Justus von Liebig in 1824 through the Grand Duchy—against the will of the university on the recommendation of Alexander von Humboldt —a new era in the natural sciences began, not only in Giessen. Young, promising scientists created a new impulse in their respective areas of knowledge; among these scientists were the antiquarian Friedrich Gottlieb Welcker ,
27482-449: The same time. Each pyruvate is then oxidized into acetyl-CoA by the pyruvate dehydrogenase complex , which also generates NADH and carbon dioxide. Acetyl-CoA enters the citric acid cycle, which takes places inside the mitochondrial matrix. At the end of the cycle, the total yield from 1 glucose (or 2 pyruvates) is 6 NADH, 2 FADH 2 , and 2 ATP molecules. Finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in
27664-408: The scarcest available resource. A plant's development is limited by the one essential mineral that is in the relatively shortest supply. This concept of limitation can be visualized as "Liebig's barrel", a metaphorical barrel in which each stave represents a different element. A nutrient stave that is shorter than the others will cause the liquid contained in the barrel to spill out at that level. This
27846-676: The second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate (RuBP) in a sequence of light-independent (or dark) reactions called the Calvin cycle . Cell signaling (or communication) is the ability of cells to receive, process, and transmit signals with its environment and with itself. Signals can be non-chemical such as light, electrical impulses , and heat, or chemical signals (or ligands ) that interact with receptors , which can be found embedded in
28028-460: The skin, lungs, and other organs, potentially spreading contagion. Again, although the world was much more complicated than his theory, and many of his individual ideas were later proved wrong, Liebig managed to synthesize existing knowledge in a way that had implications for doctors, sanitarians, and social reformers. The English medical journal The Lancet reviewed Liebig's work and translated his chemical lectures as part of its mission to establish
28210-553: The skin. Their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles: carbon fixation; nitrogen cycling; organic compound turnover; and maintaining microbial symbiotic and syntrophic communities, for example. Eukaryotes are hypothesized to have split from archaea, which was followed by their endosymbioses with bacteria (or symbiogenesis ) that gave rise to mitochondria and chloroplasts, both of which are now part of modern-day eukaryotic cells. The major lineages of eukaryotes diversified in
28392-476: The stroma. This is analogous to the proton-motive force generated across the inner mitochondrial membrane in aerobic respiration. During the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the ATP synthase is coupled to the synthesis of ATP by that same ATP synthase. The NADPH and ATPs generated by the light-dependent reactions in
28574-505: The theoretical implications of their results. Liebig published on a wide variety of topics, personally averaging 30 papers per year between 1830 and 1840. Liebig not only isolated individual substances, but also studied their interrelationships and the ways in which they degraded and metamorphosed into other substances, looking for clues to the understanding of both chemical composition and physiological function. Other significant contributions by Liebig during this time include his examination of
28756-471: The third tenet, and by the 1860s most biologists accepted all three tenets which consolidated into cell theory . Meanwhile, taxonomy and classification became the focus of natural historians. Carl Linnaeus published a basic taxonomy for the natural world in 1735, and in the 1750s introduced scientific names for all his species. Georges-Louis Leclerc, Comte de Buffon , treated species as artificial categories and living forms as malleable—even suggesting
28938-504: The three lower bulbs and used to measure the weight of carbon in the sample. For any substance consisting only of carbon, hydrogen, and oxygen, the percentage of oxygen was found by subtracting the carbon and hydrogen percentages from 100%; the remainder must be the percentage of oxygen. A charcoal furnace (a sheet steel tray in which the combustion tube was laid) was used for the combustion. Weighing carbon and hydrogen directly, rather than estimating them volumetrically, significantly increased
29120-439: The total number of chromosomes is maintained. In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA is replicated) and is often followed by telophase and cytokinesis ; which divides the cytoplasm , organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis all together define
29302-431: The underlying genotype of an organism with a dominant phenotype. A Punnett square can be used to predict the results of a test cross. The chromosome theory of inheritance , which states that genes are found on chromosomes, was supported by Thomas Morgans 's experiments with fruit flies , which established the sex linkage between eye color and sex in these insects. A gene is a unit of heredity that corresponds to
29484-536: The university got its original name "Ludoviciana", founded his own institution of higher education in Giessen, which as a Lutheran institution had the primary function of ensuring the education of pastors and civil servants. Endowed with a charter issued by Rudolf II, Holy Roman Emperor , on 19 May 1607, the university was allowed to proceed with instruction in October 1607. During the Thirty Years' War , when Hesse-Darmstadt
29666-433: The university's central building (inaugurated 1880) and the adjacent newly constructed facilities for chemistry and physics a new cultural centre was established on what was then the border of the city. The decisive backer of this project was the last Grand Duke Ernst Ludwig, to whom the university bestowed out of thankfulness the honorary title of "Rector Magnificentissimus". In 1902 the student body surpassed one thousand. For
29848-416: The university. From 1825 to 1835, the laboratory was housed in the guardroom of a disused barracks on the edge of town. The main laboratory space was about 38 m (410 sq ft) in size and included a small lecture room, a storage closet, and a main room with ovens and work tables. An open colonnade outside could be used for dangerous reactions. Liebig could work there with eight or nine students at
30030-506: The unusually diverse course offerings that continue to exist to the modern day at the University of Giessen. The University of Giessen weathered the transition from the 18th to the 19th century unscathed and was still the only university of an enlarged territory, the Grand Duchy of Hesse . Alongside Jena, Giessen was the prototype for the politicized Vormärz university, and the "Giessener Schwarzen" with Karl Follen and Georg Büchner , marked
30212-559: The way for Liebig to apply for a full professorship. Liebig was appointed to the Ordentlicher chair in chemistry on 7 December 1825, receiving a considerably increased salary and a laboratory allowance. Liebig married Henriette "Jettchen" Moldenhauer (1807–1881), the daughter of a state official, in May 1826. They had five children: Georg (1827–1903), Agnes (1828–1862), Hermann (1831–1894), Johanna (1836–1925), and Marie (1845–1920). Although Liebig
30394-410: The work of Carl Vogt (1817–1895), Jacob Moleschott (1822–1893), and Ludwig Büchner (1824–1899). By the 1840s, Liebig was attempting to apply theoretical knowledge from organic chemistry to real-world problems of food availability. His book Die organische Chemie in ihrer Anwendung auf Agricultur und Physiologie ( Organic Chemistry in its Application to Agriculture and Physiology ) (1840) promoted
30576-429: The world around them. Life on Earth, which emerged more than 3.7 billion years ago, is immensely diverse. Biologists have sought to study and classify the various forms of life, from prokaryotic organisms such as archaea and bacteria to eukaryotic organisms such as protists , fungi, plants, and animals. These various organisms contribute to the biodiversity of an ecosystem , where they play specialized roles in
30758-409: The world's first infant formula , a breast-milk substitute for babies who could not breast-feed. However, the product proved controversial, even though Liebig did not make any royalties off it. Liebig first came up with the idea based on the struggles of his favorite daughter, Johanna, who struggled to breastfeed her daughter, Carolina, who was born in 1864. (Johanna did not want to seek a wet-nurse ,
30940-568: Was Friedrich Wöhler . They met in 1826 in Frankfurt, after independently reporting on the preparation of two substances, cyanic acid and fulminic acid , that apparently had the same composition, but very different characteristics. The silver fulminate investigated by Liebig, was explosive, whereas the silver cyanate found by Wöhler, was not. After reviewing the disputed analyses together, they agreed that both were valid. The discovery of these and other substances led Jöns Jacob Berzelius to suggest
31122-506: Was Lutheran and Jettchen Catholic, their differences in religion appear to have been resolved amicably by bringing their sons up in the Lutheran faith and their daughters as Catholics. Liebig and several associates proposed to create an institute for pharmacy and manufacturing within the university. The Senate, however, uncompromisingly rejected their idea, stating that training "apothecaries, soapmakers, beer-brewers, dyers and vinegar-distillers"
31304-472: Was a drysalter and hardware merchant who compounded and sold paints, varnishes, and pigments , which he developed in his own workshop. From childhood, Justus was fascinated with chemistry . At the age of 13, Liebig lived through the year without a summer , when the majority of food crops in the Northern Hemisphere were destroyed by a volcanic winter . Germany was among the hardest-hit nations in
31486-452: Was able to take the area around Marburg for itself, the University of Giessen ceased instruction and was moved back to its more long-standing location in Marburg (1624/25). The Peace of Westphalia led to the restoration of the old location and in 1650 to the relocation of the university to Giessen. In the 17th and 18th centuries the Ludoviciana was a typical small state university that then had
31668-511: Was apprenticed for several months to the apothecary Gottfried Pirsch (1792–1870) in Heppenheim before returning home, possibly because his father could not afford to pay his indentures (a legal contract that reflects or covers a debt or purchase obligation). He worked with his father for the next two years, then attended the University of Bonn , studying under Karl Wilhelm Gottlob Kastner , his father's business associate. When Kastner moved to
31850-514: Was commissioned in England to write Practical Cookery Book for the Liebig Company. In the United States, Maria Parloa extolled the benefits of Liebig's extract. Colorful calendars and trading cards were also marketed to popularize the product. The company also worked with British chemist Henry Enfield Roscoe to develop a related product, which it registered some years after Liebig's death, under
32032-505: Was known to be taken in and oxygen released during photosynthesis, but researchers suggested that oxygen was obtained from carbon dioxide, rather than from water. Hydrogen was believed to come primarily from water. Researchers disagreed about whether sources of carbon and nitrogen were atmospheric or soil-based. Nicolas-Théodore de Saussure 's experiments, reported in Recherches Chimiques sur la Végétation (1804), suggested that carbon
32214-434: Was launched in 1990 to map the human genome . All organisms are made up of chemical elements ; oxygen , carbon , hydrogen , and nitrogen account for most (96%) of the mass of all organisms, with calcium , phosphorus , sulfur , sodium , chlorine , and magnesium constituting essentially all the remainder. Different elements can combine to form compounds such as water, which is fundamental to life. Biochemistry
32396-511: Was not the university's task. As of 17 December 1825, they ruled that any such institution would have to be a private venture. This decision worked to Liebig's advantage. As an independent venture, he could ignore university rules and accept matriculated and unmatriculated students. Liebig's institute was widely advertised in pharmaceutical journals and opened in 1826. Its classes in practical chemistry and laboratory procedures for chemical analysis were taught in addition to Liebig's formal courses at
32578-462: Was obtained from atmospheric rather than soil-based sources. It also indicated that water was a likely source of hydrogen. He also studied the absorption of minerals by plants, and observed that mineral concentrations in plants tended to reflect their presence in the soil in which the plants were grown. However, the implications of De Saussure's results for theories of plant nutrition were neither clearly discussed nor easily understood. Liebig reaffirmed
32760-440: Was sufficiently supplied by precipitation of ammonia from the atmosphere, and argued vehemently against the use of nitrogen-based fertilizers for many years. An early commercial attempt to produce his own fertilizers was unsuccessful, due to lack of nitrogen in the mixtures. When tested in a farmer's field, Liebig's manure was found to have no appreciable effect. Liebig's difficulties in reconciling theory and practice reflected that
32942-441: Was the lack of instruments and methods of analysis to support accurate, replicable analyses of organic materials. Many chemists worked on the problem of organic analysis, including French Joseph Louis Gay-Lussac and Swedish Jöns Jacob Berzelius , before Liebig developed his version of an apparatus for determining the carbon, hydrogen, and oxygen content of organic substances in 1830. It involved an array of five glass bulbs, called
33124-412: Was used pharmaceutically, and certainly made possible many contributions to organic, agricultural and biological chemistry. Liebig also popularized the use of a counter-current water-cooling system for distillation, still referred to as a Liebig condenser . Liebig himself attributed the vapor condensation device to German pharmacist Johann Friedrich August Gottling , who had made improvements in 1794 to
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