chapter 8

The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules.

An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.

(1) The overall flow and transformation of energy in an organism. (2) The study of how energy flows through organisms.

A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules.

A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

Energy available in molecules for release in a chemical reaction; a form of potential energy.

An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.

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.

A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics.

A nonspontaneous chemical reaction in which free energy is absorbed from the surroundings.

In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.

A measure of molecular disorder, or randomness.

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.

A temporary complex formed when an enzyme binds to its substrate molecule(s).

A spontaneous chemical reaction in which there is a net release of free energy.

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

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 (ΔG) is calculated by the equation ΔG = ΔH - TΔS, where ΔH is the change in enthalpy (in biological systems, equivalent to total energy), ΔT is the absolute temperature, and ΔS is the change in entropy.

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.

The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.

A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway).

The totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.

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.

A molecule (often a reactant) with a phosphate group covalently bound to it, making it more reactive (less stable) than the unphosphorylated molecule.

The energy that matter possesses as a result of its location or spatial arrangement (structure).

The reactant on which an enzyme works.

Kinetic energy due to the random motion of atoms and molecules; energy in its most random form. See also heat.