BI134 Foundations of Cell Biology - Enzymes & Enzyme Regulation

Vocabulary flashcards covering enzymes, their function, regulation, and related concepts from lecture notes.

Enzyme

A protein that functions as a catalyst to accelerate chemical reactions by lowering activation energy and regulating cellular activity.

Activation energy

The minimum energy required for a reaction to proceed; enzymes lower this barrier to speed up reactions.

Substrate

The reactant(s) that bind to the enzyme's active site and are converted to product(s).

Active site

The region of the enzyme where the substrate binds; its shape determines specificity.

Enzyme-substrate complex

The temporary complex formed when the substrate binds to the enzyme before product formation.

Product

The molecules produced after the enzymatic reaction.

Specificity

The selective interaction of an enzyme with particular substrates, determined by the active site shape.

Lock-and-key model

A model in which the substrate fits the active site exactly like a key fits a lock.

Induced fit

The enzyme changes shape slightly when the substrate binds, enhancing catalysis.

Amylase

An enzyme that hydrolyzes starch to glucose; does not act on proteins.

Protease

An enzyme that breaks down proteins into amino acids; does not affect starch.

Temperature effect on enzyme activity

Enzyme activity increases with temperature up to an optimum, then declines with excessive heat.

pH effect on enzyme activity

Enzyme activity varies with pH; each enzyme has an optimal pH range.

Allosteric regulation

Regulation by regulatory molecules that bind to sites other than the active site, causing activation or inhibition.

Allosteric site

An alternate regulatory site on an enzyme where activators or inhibitors bind.

Activator

A regulatory molecule that increases enzyme activity by binding to the enzyme (often at an allosteric site).

Inhibitor

A regulatory molecule that decreases enzyme activity by binding and altering enzyme function.

Competitive inhibitor

Binds to the enzyme's active site, blocking substrate binding; effect can be overcome by higher substrate concentration.

Non-competitive inhibitor

Binds to a site other than the active site, changing enzyme shape and reducing activity; cannot be overcome by increases in substrate.

Apoenzyme

The inactive protein portion of an enzyme that requires a cofactor or coenzyme to become active.

Holoenzyme

The active enzyme formed when an apoenzyme binds its cofactor or coenzyme.

Cofactor

A nonprotein molecule required for enzyme activity, often an inorganic ion such as Fe2+ or Mg2+.

Coenzyme

An organic molecule, often a vitamin or vitamin-derived, that activates an apoenzyme.

Compartmentalization

Storing enzymes in specific cellular locations (organelles or membranes) to restrict reactions to particular compartments.

Feedback inhibition

The product of a pathway inhibits an early enzyme, slowing or stopping production when enough product has formed.

Reversible regulation

Regulatory interactions between enzymes and regulators that are reversible; removing the regulator restores the enzyme to its original state.