|
Pasteur Point
The Pasteur point is a level of oxygen (about 0.3% by volume which is less than 1% of Present Atmospheric Level or PAL) above which facultative aerobic microorganisms and facultative anaerobes adapt from fermentation to aerobic respiration. It is also used to mark the level of oxygen in the early atmosphere of the Earth that is believed to have led to major evolutionary changes. It is named after Louis Pasteur, the French microbiologist who studied anaerobic microbial fermentation, and is related to the Pasteur effect. It was once supposed that about 400 million years ago, in the Cambrian period, the level of oxygen in the atmosphere rose from 0.1 to 1 percent of present atmospheric level. Supposedly, this led to many organisms adapting from fermentation to respiration, leading to organisms evolving photosynthesis and what is termed the Cambrian explosion of species. It has also been suggested that this increased oxygen level reduced the influence of ultraviolet radiation.Berkner, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facultative Anaerobic Organism
A facultative anaerobic organism is an organism that makes Adenosine triphosphate, ATP by aerobic respiration if oxygen is present, but is capable of switching to Fermentation (biochemistry), fermentation if oxygen is absent. Some examples of facultatively anaerobic bacteria are ''Staphylococcus'' Species, spp., ''Escherichia coli'', ''Salmonella'', ''Listeria'' spp., ''Shewanella oneidensis'' and ''Yersinia pestis''. Certain eukaryotes are also facultative anaerobes, including fungi such as ''Saccharomyces cerevisiae'' and many aquatic invertebrates such as Nereid (worm), nereid polychaetes. See also * Aerobic respiration * Anaerobic respiration * Fermentation * Obligate aerobe * Obligate anaerobe * Microaerophile References External links Facultative Anaerobic Bacteria {{Bacteria Anaerobic respiration Cellular respiration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fermentation (biochemistry)
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology. In microorganisms, fermentation is the primary means of producing adenosine triphosphate (ATP) by the degradation of organic nutrients anaerobically. Humans have used fermentation to produce foodstuffs and beverages since the Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid found in such sour foods as pickled cucumbers, kombucha, kimchi, and yogurt, as well as for producing alcoholic beverages such as wine and beer. Fermentation also occurs within the gastrointestinal tracts of all an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerobic Respiration
Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be described as a set of metabolic reactions and processes that take place in the cells of organisms 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 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 is an unusual one because of the slow, controlled release of energy from the series of reactions. Nutrients that are commonly used by animal and pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Pasteur
Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization, the latter of which was named after him. His research in chemistry led to remarkable breakthroughs in the understanding of the causes and preventions of diseases, which laid down the foundations of hygiene, public health and much of modern medicine. His works are credited to saving millions of lives through the developments of vaccines for rabies and anthrax. He is regarded as one of the founders of modern bacteriology and has been honored as the "father of bacteriology" and the "father of microbiology" (together with Robert Koch; the latter epithet also attributed to Antonie van Leeuwenhoek). Pasteur was responsible for disproving the doctrine of spontaneous generation. Under the auspices of the French Academy of Sciences, his experiment demonstrated that in sterilized ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pasteur Effect
The Pasteur effect describes how available oxygen inhibits ethanol fermentation, driving yeast to switch toward aerobic respiration for increased generation of the energy carrier adenosine triphosphate (ATP). Discovery The effect was described by Louis Pasteur in 1857 in experiments showing that aeration of yeasted broth causes cell growth to increase while the fermentation rate decreases, based on lowered ethanol production. Explanation Yeast fungi, being facultative anaerobes, can either produce energy through ethanol fermentation or aerobic respiration. When the O2 concentration is low, the two pyruvate molecules formed through glycolysis are each fermented into ethanol and carbon dioxide. While only 2 ATP are produced per glucose, this method is utilized under anaerobic conditions because it oxidizes the electron shuttle NADH into NAD+ for another round of glycolysis and ethanol fermentation. If the concentration of oxygen increases, pyruvate is instead converted to acety ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Period
The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water – hence the name ''photosynthesis'', from the Greek ''phōs'' (), "light", and ''synthesis'' (), "putting together". Most plants, algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis 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. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centers that contain green chlorophyll (and other colored) pigments/chromoph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Explosion
The Cambrian explosion, Cambrian radiation, Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately in the Cambrian Period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well. Before early Cambrian diversification, most organisms were relatively simple, composed of individual cells, or small multicellular organisms, occasionally organized into colonies. As the rate of diversification subsequently accelerated, the variety of life became much more complex, and began to resemble that of today. Almost all present-day animal phyla appeared during this period, including the earliest chordates. A 2019 paper suggests that the timing should be expanded back to include the late Ediacaran, rather than just the n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet Radiation
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For hum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Oxygenation Event
The Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxygen Catastrophe, the Oxygen Revolution, the Oxygen Crisis, or the Oxygen Holocaust, was a time interval during the Paleoproterozoic era when the Earth's atmosphere and the shallow ocean first experienced a rise in the amount of oxygen. This began approximately 2.460–2.426 Ga (billion years) ago, during the Siderian period, and ended approximately 2.060 Ga, during the Rhyacian. Geological, isotopic, and chemical evidence suggests that biologically-produced molecular oxygen (dioxygen, O2) started to accumulate in Earth's atmosphere and changed it from a weakly reducing atmosphere practically free of oxygen into an oxidizing atmosphere containing abundant oxygen, with oxygen levels being as high as 10% of their present atmospheric level by the end of the GOE. The sudden injection of toxic oxygen into an anaerobic biosphere may have caused the extinction of many existing anaerobic species o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian Events
The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution Of The Biosphere
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evolution by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Great Oxygenation Event")
