Free Mode of Enzyme Action MCQs with Answers
22 Mode of Enzyme Action MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Enzyme action depends on the active site forming a temporary enzyme substrate complex, then converting substrate into products with lower activation energy. The lock and key and induced fit models explain specificity and binding, while cofactors and changes in enzyme shape can affect catalysis.
Last updated
22 questions · page 1 of 2
- A. raising the temperature of the reaction mixture
- B. lowering the activation energy of the reaction
- C. changing the equilibrium position in favour of the products
- D. supplying the energy the reaction needs
Explanation: An enzyme provides an alternative route with a lower activation energy, so a much larger fraction of molecules has enough energy to react…
Correct answer: lowering the activation energy of the reaction- A. is already an exact complement of the substrate before binding
- B. changes shape slightly as the substrate binds
- C. plays no part in catalysis
- D. binds any substrate regardless of shape
Explanation: Koshland's induced fit model replaced the rigid lock and key picture: the active site is flexible and moulds itself around the substrate…
Correct answer: changes shape slightly as the substrate binds- A. Koshland
- B. Emil Fischer
- C. Michaelis
- D. James Sumner
Explanation: Fischer suggested in 1894 that the substrate fits the active site as a key fits a lock, which explained specificity but treated the site…
Correct answer: Emil Fischer- A. the total number of amino acids in the molecule
- B. the temperature at which it works
- C. the shape and charge distribution of its active site
- D. the concentration of the substrate available
Explanation: Only a substrate whose shape and charges are complementary to the active site can bind, which is why sucrase acts on sucrose but not on…
Correct answer: the shape and charge distribution of its active site- A. released when the products are formed
- B. stored in the bonds of the substrate
- C. needed to bring the reactants to the transition state so the reaction can proceed
- D. used by the enzyme to bind the substrate
Explanation: Even an energetically favourable reaction needs an initial input to break existing bonds and reach the unstable transition state, and that…
Correct answer: needed to bring the reactants to the transition state so the reaction can proceed- A. The entire enzyme surface
- B. A specific region where substrate binds
- C. The coenzyme binding site
- D. Where allosteric regulators bind
Explanation: The active site is a specific pocket or cleft on the enzyme where the substrate binds and catalysis occurs.
Correct answer: A specific region where substrate binds- A. The active site is rigid
- B. The enzyme changes shape to fit the substrate
- C. The substrate is unchanged
- D. No conformational changes occur
Explanation: Koshland's induced fit model proposes that the enzyme's active site is flexible and changes shape to better accommodate the substrate.
Correct answer: The enzyme changes shape to fit the substrate- A. Rigid and specific
- B. Flexible and specific
- C. Rigid and non specific
- D. Flexible and non specific
Explanation: Fischer's lock and key model treats the active site as a pre formed rigid shape that only the matching substrate fits, which explains…
Correct answer: Rigid and specific- A. Endonuclease
- B. Exonuclease
- C. S 1 nuclease
- D. Deoxyribonuclease
Explanation: Exonucleases remove nucleotides one at a time from the free ends of DNA or RNA strands.
Correct answer: Exonuclease- 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. The active site is rigid in nature
- B. The active site is complementary to substrate
- C. The enzyme can react with specific substrates only
- D. The enzyme can react with a wide range of substrates
Explanation: In the lock and key model of enzyme action, the enzyme's active site is specifically shaped to fit only its corresponding substrate, much…
Correct answer: The enzyme can react with a wide range of substrates- A. A
- B. B
- C. C
- D. D
Explanation: B is marked on the graph for an enzyme catalyzed reaction. It represents the transition state wher Subtrate molecules are highly unstable.
Correct answer: B- A. The binding of the active site to the substrate causes the enzyme to change shape
- B. The substrate and active site have complementary shapes that form temporary bonds
- C. The substrate causes a change in enzymes shape so the active site can bind
- D. The substrate changes shape so it can bind to the active site
Explanation: a) The binding of the active site to the substrate causes the enzyme to change shape:This option describes the induced fit model…
Correct answer: The binding of the active site to the substrate causes the enzyme to change shape- A. Koshland
- B. Robin Williams
- C. Rudolph Virchow
- D. Emil Fischer
Explanation: The lock and key model was proposed by Emil Fischer who was a german scientist and receiver of the nobel prize in chemistry.
Correct answer: Emil Fischer- A. Reactants
- B. Enzymes
- C. Products
- D. All of these
Explanation: The substrate bind to the enzyme which acts as catalysts in the conversion of the substrate to the product.
Correct answer: Products- A. Change in pH of enzyme
- B. Formation of ES complex
- C. Change in the shape of substrate
- D. Change in temperature
Explanation: B is correct .Formation of Enzyme Substrate complex is the step causes activation of catalytic site of an enzyme.
Correct answer: Formation of ES complexMode of Enzyme Action MCQs: common questions
Are these Mode of Enzyme Action MCQs free?
Yes. All Mode of Enzyme Action MCQs from Biology are free on TestUstad, with unlimited attempts and no account needed. Nothing on this page is a sample or a trial.
How many Mode of Enzyme Action MCQs are on this page?
There are 22 Mode of Enzyme Action MCQs in the Biology bank, shown 20 to a page with the correct answer and an explanation on each.
Does every Mode of Enzyme Action MCQ have an explanation?
Yes. Each Mode of Enzyme Action question shows the correct option and a written explanation of why it is correct, so a wrong answer teaches you something rather than just being marked wrong.
Can I take a timed Mode of Enzyme Action test?
Yes. The practice button on this page starts a free Mode of Enzyme Action test drawn from the Biology bank. It marks each answer instantly, gives you a score at the end, and can be retaken as many times as you like.