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By lowering the activation energy, the enzyme speeds up that reaction by a rate of 10 11 or more; a reaction that would normally take over 3,000 years to complete spontaneously might take less than a second with an enzyme. The enzyme itself is not used up in the process and is free to catalyze the same reaction with a new set of substrates.
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Response to stimuli: a response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.
Some argued that the beginning of biochemistry may have been the discovery of the first enzyme, diastase (today called amylase), in 1833 by Anselme Payen, [2] while others considered Eduard Buchner's first demonstration of a complex biochemical process alcoholic fermentation in cell-free extracts to be the birth of biochemistry.
The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH 2) 2 CO from ammonia (NH 3). Animals that use this cycle, mainly amphibians and mammals, are called ureotelic. The urea cycle converts highly toxic ammonia to urea for excretion. [1]
In animals, the processes of alternating cycles of biochemical reactions of ATP synthesis and cleavage occur automatically. Moreover, the processes of alternating cycles of biochemical reactions at the levels of organs, systems and the whole organism, for example, respiration , heart contractions and others occur with different periods and ...
The basic unit of the Reactome database is a reaction; reactions are then grouped into causal chains to form pathways [115] The Reactome data model allows us to represent many diverse processes in the human system, including the pathways of intermediary metabolism, regulatory pathways, and signal transduction, and high-level processes, such as ...
In biochemical reactions, the redox reactions are sometimes more difficult to see, such as this reaction from glycolysis: P i + glyceraldehyde-3-phosphate + NAD + → NADH + H + + 1,3-bisphosphoglycerate. In this reaction, NAD + is the oxidant (electron acceptor), and glyceraldehyde-3-phosphate is the reductant (electron donor).