Free Enzymes MCQs with Answers
633 Enzymes MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Enzymes are biological catalysts that lower activation energy without being consumed, and their specificity is explained by the lock and key and induced fit models. Work includes the effects of temperature, pH and substrate concentration on reaction rate, plus competitive and non-competitive inhibition and how these differ.
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Read the Enzymes notesFree MDCAT chapter notes with key terms633 questions · page 6 of 32
- A. Never changes
- B. Forms no chemical bond with substrate
- C. Determined by structure and the specificity of the enzyme
- D. They are non specific in their action
Explanation: The active site's shape and chemical groups arise from the enzyme's three-dimensional structure, giving the enzyme specificity for…
Correct answer: Determined by structure and the specificity of the enzyme- A. Specific enzyme can transform only a specific substrate
- B. Active site of an enzyme is a non flexible structure
- C. Active site does not change before during or even after the reaction
- D. It explains the mechanism of every chemical reaction
Explanation: The lock-and-key model proposes a relatively rigid active site and specificity between an enzyme and its substrate, but it does not…
Correct answer: It explains the mechanism of every chemical reaction- A. Active site
- B. Binding site
- C. Catalytic site
- D. Allosteric site
Explanation: The active site is the three-dimensional region of an enzyme with a specific shape and chemical environment that binds the substrate and…
Correct answer: Active site- A. Change in pH of the surroundings.
- B. Formation of Enzyme Susstrate complex.
- C. Change in the charge of the active site.
- D. Change in temperature
Explanation: When an enzyme-substrate complex forms, interactions between the substrate and active site can produce induced fit, positioning catalytic…
Correct answer: Formation of Enzyme Susstrate complex.- A. Emil Fischer
- B. Koshland
- C. Robin Williams
- D. Rudolph Virchow
Explanation: Emil Fischer proposed the lock-and-key model, in which the substrate has a shape complementary to the enzyme's relatively rigid active…
Correct answer: Emil Fischer- A. derived from vitamins.
- B. composed of amino acids.
- C. loosely attached to enzymes.
- D. covalently attached to enzymes.
Explanation: Prosthetic groups are non-protein molecules that are covalently attached to an enzyme, making them a permanent part of the enzyme's…
Correct answer: covalently attached to enzymes.107. The enzymes which catalyse the non-hydrolytic removal of a chemical group from a substrate are:
- A. Lyases
- B. Ligases
- C. Isomerases
- D. Transferases
Explanation: Lyases are a class of enzymes that catalyze the non-hydrolytic removal or addition of groups to substrates, often resulting in the…
Correct answer: Lyases- A. Lyases
- B. Ligases
- C. Hydrolases
- D. Isomerases
Explanation: The correct answer is ligases. RNA polymerase catalyzes the formation of phosphodiester bonds between RNA nucleotides, which is…
Correct answer: Ligases- A. oxidoreductases
- B. Hydrolases
- C. Transferases
- D. lyases
Explanation: These enzymes catalyze the transfer of specific functional group other than hydrogen from one substrate to another.
Correct answer: Transferases- A. Substrate
- B. Coenzyme
- C. Apoenzyme
- D. Holoenzyme
Explanation: An activated enzyme made of a polypeptide chain and a cofactor is referred to as a "holoenzyme." The holoenzyme is the complete…
Correct answer: Holoenzyme- A. Isoenzyme
- B. Coenzyme
- C. Holoenzyme
- D. Apoenzyme
Explanation: The correct term for an organic substance bound to an enzyme and essential for its activity is a "coenzyme." A coenzyme is a non-protein…
Correct answer: Coenzyme- A. Coenzyme
- B. Prosthetic group
- C. Holoenzyme
- D. Activator
Explanation: The detachable cofactor is known as an activator if it is an inorganic ion.
Correct answer: Activator- A. Prosthetic group
- B. Activator
- C. Coenzyme
- D. Inhibitor
Explanation: Some enzymes use metal ions as cofactors like Mg2+,Fe2+,Cu2+,Zn2+ etc. The detachable cofactor is known as an activator if it is an…
Correct answer: Activator- A. Hydrogen, Ionic
- B. Hydrogen, Covalent
- C. Ionic, Hydrogen
- D. Covalent, Ionic
Explanation: Enzymes are proteins in nature, and different types of bonds (Hydrogen and Ionic) maintain their structure.
Correct answer: Hydrogen, Ionic- A. activate the enzymes
- B. alter the rate of reactions
- C. minimize the energy efficiency
- D. regulate the amount of product
Explanation: Feedback inhibition is a regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme involved early in the…
Correct answer: regulate the amount of product- A. allosteric inhibitor
- B. irreversible inhibitor
- C. competitive inhibitor
- D. non-competitive inhibitor
Explanation: Malonate is a competitive inhibitor, which means it competes with the substrate for the active site of the enzyme.
Correct answer: competitive inhibitor- A. X: substrate, Y: non-competitive inhibitor Z: enzyme
- B. X: non-competitive inhibitor Y: enzyme Z: substrate
- C. X: substrate Y: competitive inhibitor Z: enzyme
- D. X: competitive inhibitor Y: non-competitive inhibitor Z: substrate
Explanation: In an enzyme-controlled reaction, the substrate (X) is the molecule upon which the enzyme (Z) acts.
Correct answer: X: substrate, Y: non-competitive inhibitor Z: enzyme- A. Reversible and Competitive inhibitor
- B. Irreversible and Competitive inhibitor
- C. Reversible and Non-competitive inhibitor
- D. Irreversible and Non-competitive inhibitor
Explanation: Inhibitors that do not change Vmax are typically competitive inhibitors. Non-competitive inhibitors always lower the apparent Vmax.
Correct answer: Reversible and Competitive inhibitor- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: In the lock and key model, a competitive inhibitor competes with the substrate for the active site of the enzyme.
Correct answer: Option B- A. Reversible inhibitor
- B. Competitive inhibitor
- C. Non-competitive inhibitor
- D. Irreversible inhibitor
Explanation: The reversible non-competitive inhibitors inactivate the enzyme temporarily while irreversible non-competitive inhibitors denature the…
Correct answer: Irreversible inhibitor