biological reactions are regulated by enzymes

How does temperature affect enzyme activity?

Activity increases with temperature as particles gain kinetic energy, but above the optimum, enzymes denature as bonds break

What does “denaturation” mean?

A permanent change in an enzyme’s tertiary structure, causing the active site to lose its specific shape.

How does pH affect enzyme activity?

Changes in pH alter charges on amino acids, disrupting hydrogen and ionic bonds — the active site shape is altered and substrate binding is reduced.

What happens when the enzyme or substrate concentration increases?

The rate of reaction increases until a limiting factor is reached — eventually, the rate plateaus when all active sites are occupied.

What is an enzyme inhibitor?

A substance that decreases or stops enzyme activity by interfering with substrate binding or catalysis.

What is competitive inhibition?

A molecule similar in shape to the substrate competes for the active site — inhibition can be overcome by increasing substrate concentration.

What is non-competitive inhibition?

The inhibitor binds to an allosteric site (not the active site), changing the enzyme’s shape so the substrate can no longer bind — cannot be overcome by more substrate.

What is end-product inhibition?

When the final product of a metabolic pathway inhibits an enzyme earlier in the pathway, preventing overproduction.

What is a cofactor?

A non-protein substance that helps an enzyme function properly — can be inorganic ions or organic molecules

What are coenzymes?

Organic cofactors that temporarily bind to the enzyme and transfer chemical groups between reactions (e.g. NAD⁺, FAD).

What is a prosthetic group?

A tightly bound cofactor that forms a permanent part of the enzyme (e.g. Zn²⁺ in carbonic anhydrase)

Give an example of how cofactors assist enzymes

Cl⁻ ions act as cofactors for amylase, allowing the enzyme to maintain its correct shape.

What is a metabolic pathway?

A series of enzyme-controlled reactions where the product of one reaction becomes the substrate for the next

Why are metabolic pathways regulated?

To control the rate of product formation and maintain balance in the cell’s chemistry (homeostasis).

How are enzymes used in industrial processes?

They catalyse reactions under mild conditions, saving energy and increasing efficiency in industries like brewing and biotechnology

What are immobilised enzymes?

Enzymes fixed to a solid support or trapped in a gel, allowing reuse and easier separation from the reaction mixture.

What are advantages of immobilised enzymes?

Increased stability, reusability, and easy product purification.

Give an example of an immobilised enzyme used commercially.

Lactase, used to break down lactose in milk for lactose-intolerant individuals.

What variables must be controlled in enzyme experiments?

Temperature, pH, substrate concentration, and enzyme concentration.

How is enzyme activity commonly measured?

By recording the rate of product formation or substrate disappearance over time.

What is the initial rate of reaction?

The fastest rate observed at the start of a reaction when substrate concentration is highest