Energy, Enzymes, and Biological Reactions

Flashcards about energy, enzymes, and biological reactions.

Exergonic reaction

Reaction that releases free energy; ΔG is negative because the products contain less free energy than the reactants.

Endergonic reaction

Reactants must gain free energy from the surroundings to form the products; ΔG is positive because the products contain more free energy than the reactants.

Metabolic pathway

A series of reactions in which the products of one reaction are used immediately as the reactants for the next reaction in the series.

Catabolic pathway

Energy is released by the breakdown of complex molecules to simpler compounds; overall ΔG is negative.

Anabolic pathway

Energy is used to build complicated molecules from simpler ones; overall ΔG is positive.

Adenosine triphosphate (ATP)

Consists of the five-carbon sugar ribose linked to the nitrogenous base adenine and a chain of three phosphate groups.

Hydrolysis of ATP

The breakdown of ATP which results in the formation of adenosine diphosphate (ADP) and a molecule of inorganic phosphate (Pi).

Activation energy (Ea)

Small amount of energy added for a reaction to start.

Catalyst

A chemical agent that accelerates (catalyzes) the rate of a reaction without being changed by the reaction.

Enzymes

Proteins which increase the rate of reaction by lowering the activation energy of the reaction.

Substrate

The reactant that an enzyme acts on.

Active site

A small pocket or groove in the enzyme molecule where the substrate interacts.

Cofactor

A nonprotein group that binds to the enzyme, for catalytic activity.

Coenzymes

Small organic molecules (cofactors) which are often derived from vitamins.

Enzyme inhibitors

Nonsubstrate molecules that bind to an enzyme and decrease its activity.

Competitive inhibition

Inhibitors bind to the active site, blocking access for the normal substrate – slowing or stopping the reaction.

Noncompetitive inhibition

Inhibitors bind at a location other than the active site – reducing the ability of the active site to bind substrate.