OCR A Level Biology Enzymes

Which inorganic ion can act as a cofactor for amylase?

• OH⁻

• PO₄³⁻

• Cl⁻

• HCO₃⁻

Match the word about enzyme inhibition to its definition.

• Binds to allosteric site

• Reversible

• Binds to active site

• Competitive inhibitor

• Binding of inhibitor can be reversed.

• Inactivator

• Binds irreversibly to active site

• Non-reversible

• Binding of inhibitor cannot be reversed.

• Non-competitive inhibitor

Which of the following factors does not affect the shape of the active site of an enzyme?

• a drop in temperature

• non-competitive inhibitor

• a change in pH

• binding of substrate

Zinc ions are necessary for the enzyme carbonic anhydrase to work.

Which statement correctly describes the nature and function of zinc ions in their interaction with carbonic anhydrase?

• 1. inorganic ions and coenzymes

• 1. vitamins and prosthetic groups

• 1. inorganic ions and prosthetic groups

• 1. vitamins and coenzymes

Amylase activity is increased in the presence of chloride ions.

State the name given to any inorganic ion that increases the activity of an enzyme.

Catalase is an intracellular enzyme with an iron-containing haem group.

1. 
   State the term used to describe an ion that is essential for the enzyme to function.

Catalase is an intracellular enzyme with an iron-containing haem group.

1. 
   Name another conjugated protein that contains a haem group.

Match the vitamin to its derived coenzyme, or inorganic ion to its enzyme.

• Zn²⁺

• Amylase

• Coenzyme A

• Carbonic anyhydrase

• Cl^–

• Nicotinamide B3

• NAD, NADP

• Pantothenate B6

Many enzymes require cofactors, prosthetic groups and coenzymes to function.

Which of the statements is correct?

• Cl^– acts as a coenzyme for amylase

• Cl^– acts as a cofactor for carbonic anhydrase

• Zn²⁺ acts as a prosthetic group for amylase

• Zn²⁺ acts as a prosthetic group for carbonic anhydrase

What is the correct definition of the term coenzyme?

• An inorganic ion that forms the centre of a globular protein.

• A molecule that binds to the enzyme, changing the shape of the active site, preventing an enzyme substrate complex from forming.

• A non-protein organic molecule, not permanently attached to an enzyme, but needed to allow the enzyme to function.

• A metal ion that attaches to the enzyme, changing the shape of the active site, increasing the likelihood of a reaction.