Chapter 6: Metabolism

activation energy

energy necessary for reactions to occur

active site

specific region of the enzyme 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 affinity of the enzyme for its substrate

anabolic

(also, anabolism) pathways that require an input of energy 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 are broken down into simpler ones

chemical energy

potential energy in chemical bonds that is released when those bonds are broken

coenzyme

small organic molecule, such as a vitamin or its derivative, which is required to enhance the activity of an enzyme

cofactor

inorganic ion, such as iron and magnesium ions, required for optimal regulation of enzyme activity

competitive inhibition

type of inhibition in which the inhibitor competes with the substrate molecule by binding to the active site of the enzyme

denature

process that changes the natural properties of a substance

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

total energy of a system

entropy (S)

measure of randomness or disorder within a system

exergonic

describes chemical reactions that release free energy

feedback inhibition

effect of a product of a reaction sequence to decrease its further production by inhibiting the activity of the first enzyme 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 motion of molecules or particles)

heat energy

total bond energy of reactants or products in a chemical reaction

in vitro

taking place in a test tube, culture dish, or elsewhere outside a living organism

induced fit

dynamic fit between the enzyme and its substrate, in which both components modify their structures to allow for ideal binding

kinetic energy

type of energy associated 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

type of energy 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