Enzymes IGCSE Biology

What is the specific region of an enzyme where a substrate binds?

• Substrate site

• Binding site

• Active site

• Reaction site

Enzymes are used up in chemical reactions and need to be replaced.

• TRUE

• FALSE

Enzymes are biological __________ that speed up chemical reactions.

• Reactants

• Catalysts

• Products

• Substrates

What is the effect of high temperatures on enzymes?

• They work faster.

• They denature.

• They stop working permanently.

• They remain unaffected.

Which pH value is optimal for most enzymes in the human body?

• 2

• 7

• 9

• 14

What are enzymes made of?

• Lipids

• Carbohydrates

• Proteins

• Nucleic acids

Enzymes work best at specific temperatures and pH levels.

• TRUE

• FALSE

What happens when an enzyme is denatured?

• The substrate no longer fits the active site.

• The enzyme becomes more effective.

• The enzyme is permanently damaged.

• Both A and C.

What is the lock-and-key model of enzyme action?

• Enzymes are identical to their substrates.

• The enzyme's active site and the substrate fit perfectly like a lock and key.

• Enzymes change shape to fit any substrate.

• The substrate unlocks the enzyme permanently.

Enzymes that break down proteins into amino acids are called __________.

• Amylases

• Proteases

• Lipases

• Catalases