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. Active site
- B. Binding site
- C. Catalytic site
- D. Allosteric site
Explanation: Feedback inhibition is usually accomplished through something called an "allosteric site" - a site on an enzyme, that changes the shape of…
Correct answer: Allosteric site- A. Active sites
- B. Binding site
- C. Catalytic groups
- D. Allosteric sites
Explanation: The correct answer is Allosteric sites. These are sites on an enzyme other than the active site where molecules can bind to regulate the…
Correct answer: Allosteric sites- A. Irreversible inhibition
- B. Competitive inhibition
- C. Non-competitive inhibition
- D. Reversible inhibition
Explanation: Non-competitive inhibition occurs when an inhibitor binds to another part of an anzyme, denatures the active site, and inhibits the…
Correct answer: Non-competitive inhibition- A. Apoenzyme
- B. Co-factor
- C. Holoenzyme
- D. Coenzyme
Explanation: A holoenzyme is the complete, active form of an enzyme. comprising the apoenzyme and its co-factor.
Correct answer: Holoenzyme- A. 37 degrees Celsius
- B. 49 degrees Celsius
- C. 25 degrees Celsius
- D. 10 degrees Celsius
Explanation: Optimum body temprature for the enzyme to act at a maximum rate for human body is 37°
Correct answer: 37 degrees Celsius- A. Product
- B. Inhibitor
- C. Substrate
- D. Activator
Explanation: The substrate is the initial molecule upon which an enzyme acts. Here succinic acid is converted by the enzyme into fumaric acid, making…
Correct answer: Substrate- A. Oxidation of amino acid
- B. Atomization of amino acids
- C. Reduction of amino acid
- D. Ionization of amino acids
Explanation: The ionization state of amino acids is directly affected by pH. Both acidic and basic groups in amino acids can gain or lose protons based…
Correct answer: Ionization of amino acids- A. Enzyme concentration
- B. Substrate concentration
- C. Light intensity
- D. Temperature
Explanation: Light intensity does not directly affect enzyme activity because enzymes are not influenced by light.
Correct answer: Light intensity- A. Fixed temperature
- B. Optimum temperature
- C. Controlled temperature
- D. Active temperature
Explanation: The optimum temperature is the specific temperature at which an enzyme's activity is at its maximum.
Correct answer: Optimum temperature- A. Neutral
- B. Slightly alkaline
- C. Highly acidic
- D. Highly alkaline
Explanation: Enterokinase (also called enteropeptidase) functions best in a slightly alkaline environment, typically around pH 7.5-8.0, which is…
Correct answer: Slightly alkaline- A. 1
- B. 2
- C. 3
- D. 4
Explanation: Allosteric enzymes have two major sites:1. Active site where the substrate binds and the chemical reaction takes place2.
Correct answer: 2- A. Feedback inhibition
- B. Feedback regulation
- C. Positive Feedback
- D. Enzyme activation
Explanation: Feedback inhibition is a specific type of regulation where the end product of a metabolic pathway acts to decrease its own production.
Correct answer: Feedback inhibition- A. Arginase
- B. Pancreatic enzyme
- C. Catalase
- D. Chymotrypsin
Explanation: Arginase operates optimally at a pH of around 9.7. It is involved in the urea cycle, converting arginine into ornithine and urea.
Correct answer: Arginase134. Malonate is a/an:
- A. Inhibitor
- B. Product
- C. Substrate
- D. Co-factor
Explanation: Succinate dehydrogenase that catalyzes the formation of fumarate from succinate is competitively inhibited by malonate.
Correct answer: Inhibitor- A. Potential energy
- B. Radiant energy
- C. Solar energy
- D. Kinetic energy
Explanation: Heat energy increases the kinetic energy of molecules, causing them to move faster and collide more effectively, thereby activating a…
Correct answer: Kinetic energy- A. Cofactor
- B. Catalytic site
- C. Coenzyme
- D. Binding site
Explanation: The catalytic site is part of the enzyme's active site that facilitates the conversion of the ES complex into products.
Correct answer: Catalytic site- A. Transient and unstable
- B. Permanent and stable
- C. Transient but stable
- D. Permanent but unstable
Explanation: The transition state is a fleeting, highly unstable intermediate that occurs during the conversion of substrate to product, characterized…
Correct answer: Transient and unstable- A. Digestion
- B. Cellular respiration
- C. Photosynthesis
- D. Breathing
Explanation: Enzymes catalyze processes like digestion, cellular respiration, and photosynthesis, but they do not catalyze breathing, as it is a…
Correct answer: Breathing- A. Fibrous proteins
- B. No effect on end product
- C. Consumed in reaction
- D. Non-specific
Explanation: The Enzymes do not change the end product of a reaction; they only speed up the process without being consumed.
Correct answer: No effect on end product- A. Enzymes are more specific in action than catalysts
- B. Catalysts are required in larger quantities than enzymes
- C. Catalysts are generally inorganic while enzymes are organic and protein-based
- D. Enzymes require specific pH conditions, whereas catalysts do not
Explanation: Enzymes are organic molecules, primarily proteins, whereas most catalysts are inorganic substances.
Correct answer: Catalysts are generally inorganic while enzymes are organic and protein-based