B.2 Models of Enzyme Activity

Enzyme

A large molecule usually comprised of over a hundred amino acids that catalyzes biochemical reactions.

Active Site

The specific location where a substrate binds to an enzyme.

Lock and Key Model

An analogy that illustrates how enzymes and substrates fit together perfectly, like a key fitting into a lock.

E-S Complex

The combined arrangement of an enzyme and its substrate during a reaction.

Induced Fit Hypothesis

An extension of the Lock and Key Model, stating that the active site of the enzyme changes shape slightly to accommodate the substrate.

Apoenzyme

The protein component of an enzyme, which requires cofactors to be functional.

Holoenzyme

The entire enzyme complex, consisting of the apoenzyme and its cofactors.

Cofactor

A non-protein substance that assists an enzyme in its function.

Coenzyme, type of cofactor

Organic cofactors, often derived from vitamins, that assist enzymes in reactions.

NAD

Nicotinamide adenine dinucleotide, a coenzyme that acts as a hydrogen carrier in biochemical reactions.

Coenzyme A

A coenzyme derived from a B vitamin that plays a critical role in ATP generation.

Inhibitor

A substance that occupies the active site, blocking the substrate from binding and preventing a reaction.

Emil Fischer, 1894

who created the lock and key analogy

Metal ion activator

type of cofactor, which stable the electron distribution