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Probably the most important proteins, however, are the enzymes. Virtually every reaction in a living cell requires an enzyme to lower the activation energy of the reaction. These molecules recognize specific reactant molecules called substrates; they then catalyze the reaction between them.
Enzymes serve a wide variety of functions inside living organisms. They are indispensable for signal transduction and cell regulation, often via kinases and phosphatases . [ 84 ] They also generate movement, with myosin hydrolyzing adenosine triphosphate (ATP) to generate muscle contraction , and also transport cargo around the cell as part of ...
Manganese is also important in photosynthetic oxygen evolution in chloroplasts in plants. The oxygen-evolving complex (OEC) is a part of photosystem II contained in the thylakoid membranes of chloroplasts; it is responsible for the terminal photooxidation of water during the light reactions of photosynthesis , and has a metalloenzyme core ...
Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthesis) serve as enzyme substrates, with conversion by the living organism either into simpler or more complex ...
Biomolecules are an important element of living organisms. They are often endogenous, [2] i.e. produced within the organism, [3] but organisms usually also need exogenous biomolecules, for example certain nutrients, to survive. Biomolecules and their reactions are studied in biology and its subfields of biochemistry and molecular biology.
Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life. Growth: maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
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, the breaking down of glucose to pyruvate by cellular respiration ); or anabolic —the building up ( synthesis ...
It has the distinction of being the heaviest element commonly needed by living organisms as well as the second-heaviest known to be used by any form of life (only tungsten, a component of a few bacterial enzymes, has a higher atomic number and atomic weight). It is a component of biochemical pathways in organisms from all biological kingdoms ...