Enzyme Structure and Function Review

A complete set of vocabulary practice flashcards reviewing enzyme structure, catalytic activity, activation energy, regulation, and factors affecting enzyme-catalyzed reactions.

What are the monomer building blocks that cells use to synthesize enzymes?

Amino acids

How do biological catalysts accelerate metabolic chemical reactions in cells?

By lowering the activation energy ($E_A$) required for the reaction to proceed.

The specific physical pocket or cleft on an enzyme where the substrate binds

Active site

The reactant molecule that binds specifically to an enzyme's active site

Substrate

The temporary molecular structure formed when a reactant binds to an enzyme's active site

Enzyme-substrate complex

The model describing how an enzyme subtly shifts its 3D shape around the substrate upon binding to produce a tighter fit

Induced fit model

What happens to the structure and function of an enzyme once it finishes a catalytic cycle?

It remains chemically unchanged and can immediately be reused to catalyze another reaction.

Why does an enzyme lose its catalytic function when exposed to temperatures far above its optimum?

Excess heat breaks weak hydrogen and ionic bonds, causing the protein to unfold and denature, which permanently destroys the active site.

Why does an enzyme-catalyzed reaction occur much more slowly at near-freezing temperatures?

Molecules have low kinetic energy and move slowly, leading to a drastic decrease in the frequency of collisions between enzyme and substrate.

Why does reaction rate plateau when substrate concentration is increased continuously while enzyme concentration remains constant?

Enzyme saturation occurs; all available active sites are continuously occupied, capping the rate at maximum velocity.

Type of enzyme regulation where an inhibitor molecule directly blocks the catalytic active site

Competitive inhibition (which can be overcome by adding more substrate)

Type of enzyme regulation where an inhibitor binds to an allosteric site away from the active pocket, causing the active site to change shape

Noncompetitive inhibition

Non-protein organic helper molecules, often derived from dietary B vitamins, that assist enzymes during catalysis

Coenzymes

Which cellular enzyme rapidly breaks down harmful hydrogen peroxide into water and oxygen gas ($2H_2O_2 \rightarrow 2H_2O + O_2$)?

Catalase

Why does a cell need thousands of distinct enzymes rather than using a single general enzyme for all metabolic pathways?

Enzyme specificity; the precise tertiary shape and chemical properties of each active site only complement one specific substrate.

A metabolic reaction that releases energy to the surroundings and has a negative change in free energy ($\Delta G < 0$)

Exergonic reaction

A metabolic reaction that absorbs energy from the surroundings and has a positive change in free energy ($\Delta G > 0$)

Endergonic reaction