The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.
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Metabolism
The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.
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Coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.
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Entropy
A measure of molecular disorder, or randomness.
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Anabolic pathways
A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules.
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Feedback inhibition
A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.
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Chemical energy
Energy available in molecules for release in a chemical reaction; a form of potential energy.
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Allosteric regulation
The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.
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Induced fit
Caused by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate.
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Catabolic pathways
A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules.
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Enzyme
substrate complex
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Cofactors
Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely and reversibly, along with the substrate, during catalysis.
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ATP
An adenine
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Potential energy
The energy that matter possesses as a result of its location or spatial arrangement
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Metabolic pathway
A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway).
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Spontaneous process
A process that occurs without an overall input of energy; a process that is energetically favorable.
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Noncompetitive inhibitors
A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product.
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Free energy
The portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system. The change in free energy of a system (delta G) equals G(final state) minus G(initial state).
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Cooperativity
A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits.
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Endergonic reaction
A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.
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Bioenergetics
(1) The overall flow and transformation of energy in an organism. (2) The study of how energy flows through organisms.q
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First law of thermodynamics
The principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.
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Energy coupling
In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
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Energy
The capacity to cause change, especially to do work (to move matter against an opposing force).
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Phosphorylated intermediate
A molecule (often a reactant) with a phosphate group covalently bound to it, making it more reactive (less stable) than the unphosphorylated molecule.
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Exergonic reaction
A spontaneous chemical reaction, in which there is a net release of free energy.
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Thermodynamics
The study of energy transformations that occur in a collection of matter. See also first law of thermodynamics; second law of thermodynamics.
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Active site
The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.
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Second law of thermodynamics
The principle stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat.
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Enzyme
A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins.
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Substrate
The reactant on which an enzyme works.
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Catalysis
A process by which a chemical agent called a catalyst selectively increases the rate of a reaction without being consumed by the reaction.
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Heat
Thermal energy in transfer from one body of matter to another.
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Competitive inhibitors
A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics.
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