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. Changing the shape of the enzyme
- B. Merging with the substrate instead
- C. Blocking the active site of the enzyme
- D. Combining with the product of the reaction
Explanation: Blocking the active site of the enzyme: Correct answer-Competitive inhibitors block the active site by binding to it, preventing the…
Correct answer: Blocking the active site of the enzyme- A. Speed up reaction
- B. Remain unchanged after reaction
- C. Increase the activation energy
- D. Possess the active site
Explanation: Option C is correct.Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy of the reaction.
Correct answer: Increase the activation energy- A. 20°C
- B. 30°C
- C. 40°C
- D. 50°C
Explanation: Option C is correct. Enzymes in mammals typically work best at around 40°C, closely correlating with their normal body temperature of…
Correct answer: 40°C- A. Insecticides
- B. Sulphonamide
- C. Cyanide
- D. Metal ions
Explanation: Option B is correct.An example of a competitive inhibitor molecule is sulfonamide.
Correct answer: Sulphonamide- A. 4.0-5.0
- B. 1.5-1.6
- C. 8.0
- D. 6.1-6.8
Explanation: Option C is correct. The optimal pH of lipase (pancreas) is 8.0. This is the pH at which the enzyme is most active and can most…
Correct answer: 8.0- A. Reversible inhibition
- B. Competitive inhibition
- C. Non-Competitive inhibition
- D. Uncompetitive inhibition
Explanation: The correct answer is Uncompetitive inhibition. This type of inhibition specifically involves the inhibitor binding to the…
Correct answer: Uncompetitive inhibition- A. Amylase
- B. HCl
- C. Glucokinase
- D. Entrokinase
Explanation: Trypsinogen is a zymogen (inactive enzyme precursor) that requires activation to become trypsin, an active enzyme essential for protein…
Correct answer: Entrokinase- A. 2.0
- B. 7.2
- C. 8.5
- D. 9.0
Explanation: Pepsin is an enzyme found in the stomach that breaks down proteins. It works optimally in an acidic environment, with a pH around 2.0.
Correct answer: 2.0- A. Enzymes are restricted to one reaction type
- B. Enzymes are flexible and can catalyze multiple reactions
- C. Enzymes are non-specific and can bind to any substrate
- D. Enzymes are always active
Explanation: This is the correct answer. The lock-and-key model proposed by Emil Fischer suggests that enzymes are highly specific and can only…
Correct answer: Enzymes are restricted to one reaction type- A. Cofactors
- B. Other enzymes
- C. Proteins
- D. Both a and c
Explanation: Cofactors are non-protein chemical compounds or metallic ions that bind to an enzyme and are essential for the enzyme's activity.
Correct answer: Cofactors- A. Transmethylase
- B. Oxygenase
- C. Peroxidases
- D. Phosphatase
Explanation: Hydrolases are a class of enzymes that catalyze the cleavage of chemical bonds using water.
Correct answer: Phosphatase- A. Catalyst
- B. Coenzyme
- C. Cofactor
- D. Enzyme
Explanation: Flavin adenine dinucleotide (FAD) is a coenzyme, a non-protein molecule that assists enzymes in catalyzing various biochemical reactions.
Correct answer: Coenzyme- A. When few enzyme molecules are left unsaturated.
- B. When the substrate cools down.
- C. When the substrate heats up.
- D. When many enzyme molecules remain unsaturated.
Explanation: The rate of an enzyme-catalysed reaction increases with substrate concentration only until all the enzyme's active sites are occupied.
Correct answer: When few enzyme molecules are left unsaturated.- A. Maximum Temperature
- B. Minimun Temperature
- C. Favourable Temperature
- D. Optimum Temperature
Explanation: Correct, as it is the temperature at which an enzyme shows maximum activity and can regain function after temporary inactivation.
Correct answer: Optimum Temperature- A. Changing conditions within the active site
- B. Changing conditions within the protein framework
- C. Rearranging the fatty acids in the active site
- D. Distorting the molecules in the allosteric site
Explanation: Changing conditions within the active site - Correct. Enzymes reduce activation energy by stabilizing the transition state within the…
Correct answer: Changing conditions within the active site- A. Inorganic
- B. Reused
- C. Derived from vitamins
- D. Globular proteins
Explanation: Reused - Correct. Enzymes and coenzymes are not consumed in reactions and can be used repeatedly.
Correct answer: Reused- A. Prosthetic group
- B. Coenzyme
- C. Cofactor
- D. Activator
Explanation: Prosthetic group - Correct. Cyanide binds to the iron in cytochrome oxidase, a prosthetic group, inhibiting respiration
Correct answer: Prosthetic group- A. 5
- B. 1
- C. 2
- D. 3
- E. 4
Explanation: The exact percentage of coenzyme composition can vary depending on the specific enzyme and coenzyme involved, it is generally estimated…
Correct answer: 1- A. Calcium and Potassium
- B. Substrate and activators
- C. Hexokinase and glucose
- D. Magnesium and manganese
- E. Pesticides DDT and parathione
Explanation: The correct answer is E Pesticides DDT and parathione. Pesticides such as DDT (dichlorodiphenyltrichloroethane) and parathion are known to…
Correct answer: Pesticides DDT and parathione- A. Quantity of enzyme
- B. pH of enzyme
- C. Shape of enzymes
- D. Temperature of enzyme
- E. Nature of enzyme
Explanation: Exposure to UV, high-energy, and ionizing radiation, such as X-rays and gamma rays, can cause damage to enzymes and other biomolecules.
Correct answer: Shape of enzymes