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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241. A chemical substance that can react with an enzyme but not transform into a product is called a/an:
- A. Substrate
- B. Product
- C. Inhibitor
- D. Allosteric regulator
Explanation: An inhibitor is a chemical substance that can bind to an enzyme and disrupt its activity, thereby preventing or reducing the rate of a…
Correct answer: Inhibitor- A. Decrease in activation energy of the reaction
- B. Increase in enzyme concentration
- C. Change in overall enthalpy of the reaction
- D. Increase in pH of the reaction
Explanation: A. Decrease in activation energy of the reaction (Incorrect): This would enhance the reaction rate, but it won't cause loss of enzymatic…
Correct answer: Increase in pH of the reaction- A. 1
- B. 3
- C. 2
- D. 4
Explanation: In an enzyme activity, the substrate must bind with the enzyme to become a catalyst of a chemical reaction.
Correct answer: 1- A. Change in ionization of amino acids at the active site of the enzyme
- B. Change in the ionization of the substrate
- C. Increase in the rate of reaction
- D. Denaturation of the enzymes
Explanation: Enzymes are affected by changes in pH. The most favorable pH value - the point where the enzyme is most active - is known as the optimum…
Correct answer: Denaturation of the enzymes- A. Noncompetitive
- B. Uncompetitive
- C. Allosteric
- D. Competitive
Explanation: Competitive inhibitors bind to the active site of the enzyme. Therefore, increasing the amount of substrate increases the chance of…
Correct answer: Competitive- A. Enzymes
- B. Carbohydrates
- C. Vitamins
- D. Proteins
Explanation: This is the correct option. Irreversible modifications in cells often require the synthesis of new proteins, which can be structural…
Correct answer: Proteins- A. Inhibitors
- B. Polypeptide chains
- C. Active sites
- D. Temperature
Explanation: Important property of allosteric enzymes is that it also contains many polypeptide chains with multiple active and allosteric sites.
Correct answer: Polypeptide chains- A. Splitting of two molecules
- B. Oxidation of molecules
- C. Joining of molecules
- D. Both Options A and B are correct
Explanation: This option is correct. Ligase enzymes are specifically involved in catalyzing the joining or ligation of two molecules.
Correct answer: Joining of molecules- A. Can be reduced by inhibitors
- B. Is constant under standard conditions
- C. Cannot be measured
- D. Decreases as the substrate concentration increases
Explanation: Enzyme inhibitors are molecules that interact with enzymes (temporary or permanent) in some way and reduce the rate of an enzyme-catalyzed…
Correct answer: Can be reduced by inhibitors- A. Apoenzyme
- B. Null enzyme
- C. Zymogen
- D. Inhibitor
Explanation: Option A: Apoenzyme or apoprotein is an enzymatically inactive protein part of an enzyme, which requires a cofactor for its…
Correct answer: Zymogen- A. Fe3+
- B. Mn2+
- C. Co2+
- D. Mg2+
Explanation: Mg2+ is the cofactor used in the conversion of glucose to glucose-6-phosphate during glycolysis.
Correct answer: Mg2+- A. They are sensitive to heat
- B. They consist of proteins or without a non-proteins part
- C. They change the rate of catalyzed reaction
- D. They are non-specific in their action
Explanation: Enzymes are highly specific in their action.
Correct answer: They are non-specific in their action- A. Irreversible Inhibitor
- B. Reversible Inhibitor
- C. Non-competitive Inhibitor
- D. Competitive Inhibitor
Explanation: Malonic acid (also called malonate) competitively inhibits the activity of the enzyme succinate dehydrogenase during the Krebs cycle.
Correct answer: Competitive Inhibitor- A. mitochondria
- B. nucleus
- C. ribosomes
- D. chloroplast
Explanation: Glycolytic enzymes are present in the cytoplasm while the enzymes of the Krebs cycle are located in the mitochondrial matrix.
Correct answer: mitochondria- A. Allosterically
- B. Active site
- C. Doesn't bind on the enzyme
- D. Binds on the substrate
Explanation: Mixed inhibition is a type of enzyme inhibition in which the inhibitor may bind to the enzyme whether or not the enzyme has already bound…
Correct answer: Allosterically- A. Crystalline
- B. Disorganized
- C. Functional
- D. Both A and C
Explanation: Globular proteins are primarily distinguished by their functional versatility and ability to form compact, spherical structures.
Correct answer: Both A and C- A. Decrease
- B. Increase
- C. Remains same
- D. Both A and B
Explanation: If the active sites is altered, the substrate cannot fit into the active site of the enzyme and the rate of reaction will decrease.
Correct answer: Decrease- A. The enzymes get denatured at higher substrate concentration
- B. The rate of reaction is indirectly proportional to substrate concentration at this point
- C. All the active sites on enzyme molecules are occupied
- D. All of these options are correct
Explanation: When enzyme concentration is kept constant and the concentration of substrate is gradually increased, a point will come when all the…
Correct answer: All the active sites on enzyme molecules are occupied259. Which of the following strategies of enzymatic inhibition is used by noncompetitive inhibitors?
- A. Bind to substrate so that it cannot bind to the active site
- B. Target the enzyme for destruction using a protease
- C. Bind to the active site and prevent substrate from binding
- D. Bind to an allosteric site to cause a conformational shift in the enzyme
Explanation: . Option D is correct since non-competitive inhibitors bind to a site on the enzyme away from the active site, called the allosteric site.
Correct answer: Bind to an allosteric site to cause a conformational shift in the enzyme- A. Relative specificity
- B. Size specificity
- C. Group specificity
- D. None of these options are correct
Explanation: OPTION A: Bond specificity is the ability of an enzyme to bind with a particular type of substrate that has similar structures and similar…
Correct answer: Relative specificity