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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- A. Some of them consist solely of protein with no non protein part.
- B. They catalyze a chemical reaction without being utilized.
- C. All enzymes are fibrous Proteins.
- D. They without their cofactor are called apoenzyme.
Explanation: Enzymes are generally globular proteins, not fibrous proteins, because their folded three-dimensional structure creates the active site.
Correct answer: All enzymes are fibrous Proteins.- A. Prosthetic group
- B. Coenzyme
- C. Activator
- D. Cofactor
Explanation: A detachable inorganic ion that assists enzyme activity is called an activator, such as Mg2+ or Zn2+.
Correct answer: Activator- A. Cofactor
- B. Coenzymes
- C. Activator
- D. Enzymes
Explanation: Enzymes are biological catalysts, usually proteins, that speed biochemical reactions by lowering activation energy and remain chemically…
Correct answer: Enzymes- A. Vitamins
- B. Carbohydrates
- C. Proteins
- D. Metals
Explanation: Many coenzymes are derived from vitamins, especially B-group vitamins, which are converted into active coenzyme forms that carry electrons…
Correct answer: Vitamins- A. Increases
- B. Decreases
- C. Does not effect
- D. Increases or decreases depending upon individual enzyme
Explanation: Enzymes decrease activation energy by providing an alternative reaction pathway, allowing more molecules to react at a given temperature.
Correct answer: Decreases- A. bio catalyst
- B. hormone
- C. Gland
- D. None of these
Explanation: An enzyme is a biological catalyst, meaning it speeds up a biochemical reaction by lowering its activation energy without being…
Correct answer: bio catalyst- A. Co-enzyme
- B. Blocker
- C. Inhibitor
- D. Cofactor
Explanation: An inhibitor is a substance that reduces enzyme activity by binding to the enzyme; a competitive inhibitor can occupy the active site and…
Correct answer: Inhibitor- A. Irreversible inhibitor
- B. Reversible inhibitor
- C. Competitive inhibitor
- D. Non-competitive inhibitor
Explanation: A competitive inhibitor resembles the substrate and binds to the enzyme's active site, preventing the substrate from forming products.
Correct answer: Competitive inhibitor- A. Competitive inhibitors.
- B. Non-competitive inhibitors
- C. Irreversible inhibitors.
- D. Both a and b
Explanation: Weak, non-covalent bonds usually produce reversible inhibition, and both competitive and non-competitive inhibitors can act reversibly.
Correct answer: Both a and b- A. Irreversible inhibitor
- B. Reversible inhibitor
- C. Competitive inhibitor
- D. Non-competitive inhibitor
Explanation: Malonic acid resembles succinic acid and competes with it for the active site of succinate dehydrogenase, so it is a competitive…
Correct answer: Competitive inhibitor- A. Irreversible inhibitor
- B. Reversible inhibitor
- C. Competitive inhibitor
- D. Non-competitive inhibitor
Explanation: Irreversible inhibitors permanently alter an enzyme, often by forming strong covalent bonds with amino acids needed for its structure or…
Correct answer: Irreversible inhibitor- A. Substrate
- B. Co-factor
- C. Inhibitor
- D. Promotor
Explanation: An inhibitor binds to an enzyme without being converted into the normal product and can block the active site, preventing substrate…
Correct answer: Inhibitor- A. 6
- B. 7
- C. 8
- D. 9
Explanation: Salivary amylase is suited to the nearly neutral pH of the mouth and loses its functional shape in strongly alkaline conditions, such as…
Correct answer: 9- A. increase in concentration of enzyme
- B. increase in concentration of substrate
- C. increase in pH
- D. increase in temperature
Explanation: When pH and temperature are already optimal and enzyme concentration is limiting, adding more enzyme provides more active sites and…
Correct answer: increase in concentration of enzyme- A. Activate
- B. Unaffected
- C. Denatured
- D. None of these
Explanation: Excessive heat disrupts the weak bonds that maintain an enzyme's three-dimensional shape, changing the active site and causing…
Correct answer: Denatured- A. Saturation
- B. Denaturation
- C. Composition
- D. Inhibition
Explanation: When adding more substrate no longer increases the reaction rate, the enzyme's active sites are saturated and are already occupied by…
Correct answer: Saturation- A. Enzymes get denatured at higher substrate conc
- B. Rate of reaction is indirectly proportional to substrate concentration at this point
- C. All the active sites on enzyme molecule are occupied
- D. None of these
Explanation: With a fixed enzyme concentration, increasing substrate eventually occupies all available active sites, so the enzymes are working at…
Correct answer: All the active sites on enzyme molecule are occupied- A. Increase in enzyme molecule increases the available active sites.
- B. This relation is for unlimited time period with unlimited enzyme concentration
- C. If the concentration is doubled the rate will become two fold.
- D. None of these.Chemistry
Explanation: The rate is approximately directly proportional to enzyme concentration only when sufficient substrate is available and other conditions…
Correct answer: This relation is for unlimited time period with unlimited enzyme concentration- A. There is probably more substrate present than there is enzyme.
- B. There is probably more enzayme available than there is substrate.
- C. There is probably more product present than there is either substrate or enzyme.
- D. The enzyme substrate complex is probably failing to form during the reaction
Explanation: If adding substrate increases the rate, the original reaction had substrate below the level needed to occupy all available active sites…
Correct answer: There is probably more enzayme available than there is substrate.- 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