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Enzymes MCQs for MDCAT Practice

Biology section, Enzymes chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

The bank has 889 active questions on this chapter. Your first 500 practice attempts are free, and every attempt includes a worked explanation.

  1. Question 1
    In competitive Inhibition, two things attached to enzyme’s active site are:
    • Inhibitor
    • Substrate
    • Both A and B (correct answer)
    • None of these
    Correct answer: C
    Competitive inhibition involves both the substrate and inhibitor vying for the enzyme's active site, impacting enzyme kinetics.
  2. Question 2
    The competitive inhibitors have structural similarity with:
    • Active site
    • Binding site
    • Substrate (correct answer)
    • Coenzyme
    Correct answer: C
    Competitive inhibitors mimic substrates, binding to the enzyme's active site and blocking substrate access, thus affecting enzyme kinetics.
  3. Question 3
    Ribozyme is:
    • Antibiotic
    • RNA enzyme (correct answer)
    • Protein enzyme
    • Hormone
    Correct answer: B
    Ribozymes are RNA molecules with catalytic activity, challenging the traditional view of enzymes as solely protein-based catalysts. This MCQ tests your understanding of enzyme composition and function.
  4. Question 4
    Feedback inhibition is an example of which type of enzyme inhibition?
    • Competitive inhibition
    • Non competitive inhibition (correct answer)
    • Uncompetitive inhibition
    • Irreversible inhibition
    Correct answer: B
    Feedback inhibition, a crucial metabolic control, involves a final product allosterically inhibiting an early enzyme, illustrating non-competitive inhibition.
  5. Question 5
    Enzymes which are involved in transfer of electrons are known as:
    • Oxidases
    • Dehydrogenases
    • Hydrolases
    • Both A and B (correct answer)
    Correct answer: D
    Enzymes mediating electron transfer are oxidases (oxygen as acceptor) & dehydrogenases (other acceptors). Both fit the broad category.
  6. Question 6
    The Inhibitor which may destroy the Globular structure of Enzyme is:
    • Competitive
    • Non-competitive
    • Reversible
    • Irreversible (correct answer)
    Correct answer: D
    Irreversible inhibitors bind enzymes covalently, permanently altering their structure and function by destroying the globular conformation.
  7. Question 7
    Which of the following is an inactive enzyme without its cofactor?
    • Coenzyme
    • Apoenzyme (correct answer)
    • Holoenzyme
    • Denatured enzyme
    Correct answer: B
    Understand enzyme structure: apoenzymes are inactive protein components needing cofactors to become holoenzymes and function.
  8. Question 8
    Enzymes that are involved in the control and regulation of biological processes are?
    • Allosteric enzymes
    • Inhibitors
    • Regulators (correct answer)
    • None of these
    Correct answer: C
    Biological processes are controlled by regulators, which can be enzymes. Allosteric enzymes are a type of regulator, but not all regulators are allosteric enzymes.

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Read the full Enzymes chapter notes: Enzymes notes. Or browse every chapter.