Lesson 2.1.4b
2.1.4b Coenzymes, cofactors and enzyme inhibitors Quiz: OCR Biology, Unit 1
20 questions
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Lesson 2.1.4b, Coenzymes, cofactors and enzyme inhibitors: 20 multiple choice questions for the OCR Biology (H020), Unit 1: Foundations in biology, written with Revision Ninja.
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The 20 questions
-
How is a coenzyme best classified in terms of its chemical nature and binding?
- Inorganic and permanent
- Organic and temporary
- Inorganic and temporary
- Protein and permanent
-
Which vitamin group serves as a key biological source of coenzymes such as NAD?
- C vitamins
- D vitamins
- B vitamins
- A vitamins
-
What type of chemical entity is an inorganic cofactor for an enzyme?
- Protein chain
- Metal ion
- Vitamin derivative
- Organic molecule
-
Where do competitive inhibitors bind on an enzyme molecule?
- Allosteric site
- Prosthetic group
- Regulatory site
- Active site
-
Where do non-competitive inhibitors bind on an enzyme molecule?
- Catalytic cleft
- Allosteric site
- Active site
- Substrate site
-
What defines the action of a reversible enzyme inhibitor?
- Permanently alters
- Binds covalently
- Destroys structure
- Detaches easily
-
What process involves the final product of a metabolic pathway inhibiting an earlier enzyme?
- Competitive inhibition
- End-product inhibition
- Enzyme induction
- Substrate activation
-
What effect does adding excess substrate have in the presence of a competitive inhibitor?
- Restores max rate
- Prevents binding
- Stops all reaction
- Denatures enzyme
-
A reaction without inhibitor has rate 50 and with inhibitor has rate 25. What is the percentage inhibition?
- 25%
- 50%
- 75%
- 2%
-
NAD, a coenzyme in respiration, is derived from which vitamin?
- Niacin (vitamin B3)
- Vitamin D
- Vitamin C
- Vitamin K
-
What must happen to restore activity if an irreversible inhibitor binds covalently to an enzyme?
- Add excess substrate
- Wash by dilution
- Change temperature
- New enzyme synthesis
-
What effect does adding a competitive inhibitor have on a rate-substrate graph?
- Shifted left
- Lower maximum rate
- Shifted right
- Steeper gradient
-
Why does a non-competitive inhibitor reduce the maximum rate of an enzyme-catalysed reaction?
- Substrate is destroyed
- Activation energy increases
- Fewer active sites
- Enzyme concentration rises
-
Which enzyme feature makes end-product inhibition possible?
- Allosteric site
- Prosthetic group
- Coenzyme region
- Active site
-
Rate is 60 units/min without an inhibitor and 15 units/min with it. What is the percentage reduction?
- 75%
- 45%
- 15%
- 25%
-
Why does a diet lacking B vitamins reduce cellular enzyme activity?
- Substrates are blocked
- Coenzyme precursors
- Protein synthesis stops
- Active sites denature
-
Evaluate: an inhibitor's effect is reduced at high substrate concentration. Which type is most likely?
- Non-competitive inhibition
- Competitive inhibition
- Allosteric activation
- Irreversible inhibition
-
Why is non-competitive enzyme inhibition not overcome by extra substrate?
- Active site blocked
- Altered active site
- Substrate is used up
- Enzyme denatures fully
-
An inhibitor lowers the rate at low substrate but reaches normal maximum at high substrate. What is it?
- Competitive inhibitor
- Permanent inhibitor
- Non-competitive inhibitor
- Allosteric inhibitor
-
What regulatory mechanism describes an end product inhibiting the first enzyme in its pathway?
- Positive feedback
- Enzyme induction
- Negative feedback
- Competitive binding
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