57 Key Terms

activation energy
energy necessary for reactions to occur
active site
enzyme’s specific region to which the substrate binds
allosteric inhibition
inhibition by a binding event at a site different from the active site, which induces a conformational change and reduces the enzyme’s affinity for its substrate
anabolic
(also, anabolism) pathways that require an energy input to synthesize complex molecules from simpler ones
ATP
adenosine triphosphate, the cell’s energy currency
bioenergetics
study of energy flowing through living systems
catabolic
(also, catabolism) pathways in which complex molecules break down into simpler ones
chemical energy
potential energy in chemical bonds that releases when those bonds are broken
coenzyme
small organic molecule, such as a vitamin or its derivative, which is required to enhance an enzyme’s activity
cofactor
inorganic ion, such as iron and magnesium ions, required for optimal enzyme activity regulation
competitive inhibition
type of inhibition in which the inhibitor competes with the substrate molecule by binding to the enzyme’s active site
denature
process that changes a substance’s natural properties
endergonic
describes chemical reactions that require energy input
energy coupling
process during which energy released by one reaction is used to drive another reaction
enthalpy
a system’s total energy
entropy (S)
measure of randomness or disorder within a system
enzyme
proteins, comprised of amino acid chains, that perform the critical task of lowering the activation energies of chemical reactions inside the cell
exergonic
describes chemical reactions that release free energy
feedback inhibition
a product’s effect of a reaction sequence to decrease its further production by inhibiting the first enzyme’s activity in the pathway that produces it
free energy
Gibbs free energy is the usable energy, or energy that is available to do work
heat
energy transferred from one system to another that is not work (energy of the molecules’ motion or particles)
heat energy
total bond energy of reactants or products in a chemical reaction
induced fit
dynamic fit between the enzyme and its substrate, in which both components modify their structures to allow for ideal binding
kinetic energy
energy type that takes place with objects or particles in motion
metabolism
all the chemical reactions that take place inside cells, including anabolism and catabolism
phosphoanhydride bond
bond that connects phosphates in an ATP molecule
potential energy
energy type that has the potential to do work; stored energy
substrate
molecule on which the enzyme acts
thermodynamics
study of energy and energy transfer involving physical matter
transition state
high-energy, unstable state (an intermediate form between the substrate and the product) occurring during a chemical reaction

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