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. Metallic ions
- B. Organic molecules
- C. Inorganic molecules
- D. Radicals
- E. A, B and C
Explanation: Inorganic cofactors are activators while organic cofactors may be coenzymes or prosthetic groups.
Correct answer: A, B and C562. Three of the following statements about enzymes are correct and one is wrong. Which one is wrong?
- A. Enzymes require optimum pH for maximal activity
- B. Enzymes are denatured at high temperatures but in certain exceptional organisms, they are effective even at temperatures such as 80° and 90°C
- C. Enzymes are highly specific
- D. Most enzymes are proteins but some are lipids
Explanation: Enzymes are mostly proteins but some are RNA (ribozymes). No lipid which works as an enzyme is known.
Correct answer: Most enzymes are proteins but some are lipids- A. A
- B. B
- C. C
- D. D
Explanation: Every enzyme work best at its optimum pH. Pepsin optimum pH is 2. In the pH above 2 pepsin will be denatured.
Correct answer: D- A. Hydrogen, Ionic
- B. Hydrogen, Covalent
- C. Ionic, Hydrogen
- D. Covalent, lonic
Explanation: Enzymes are protein in nature and different types of bonds (Hydrogen and Ionic) maintain their structure.
Correct answer: Hydrogen, Ionic- A. Fibrous proteins
- B. No effect on end product
- C. Use in reaction
- D. Non-specific
Explanation: Ezymes are globular proteins, which act as biocatalyst and speed up biochemical reactions and their presence does not affect the nature of…
Correct answer: No effect on end product- A. Substrate
- B. Prosthetic Group
- C. Coenzymes
- D. Co-factors
Explanation: Co-factors are molecules that bind to enzymes, aiding in their function by altering the enzyme's shape, and are essential for catalytic…
Correct answer: Co-factors- A. Amylopsin
- B. Bain H1
- C. Arginase
- D. Peptidyl transferase
Explanation: Peptidyl transferase is an enzyme that is not protein in nature. It is a ribozyme, a catalytic RNA molecule found in the ribosome.
Correct answer: Peptidyl transferase- A. Enzymes are sharp in action than catalyst
- B. Catalysts used in large amount than enzymes
- C. Catalysts are inorganic while enzymes are organic in nature
- D. Enzymes need pH 1 while catalysts do not
Explanation: While catalysts can be organic or inorganic in nature, enzymes are only organic in nature.
Correct answer: Catalysts are inorganic while enzymes are organic in nature- A. All enzymes require co-factors for proper functioning
- B. Only small amount of enzymes is required.
- C. They work in vitro as well as in vivo conditions
- D. They lower activation energy
Explanation: Co-factors are non-protein parts that are required for proper functioning of enzyme but some enzymes such as pepsin do not require…
Correct answer: All enzymes require co-factors for proper functioning570. With the increase of enzyme concentration in a reaction, more_is/are available for the substrate.
- A. Binding sites
- B. Products
- C. Active site
- D. Activation energy
Explanation: When enzyme molecules increase there will be more active sites available for the binding of more substrates, due to which reaction rate…
Correct answer: Active site- A. Increase in rate of reaction
- B. Decrease in rate of reaction
- C. First increase then decrease in rate of reaction
- D. First increase then become constant
Explanation: The optimum temperature for the enzymes in human body is 37°C, When the temperature is increased from 30°C, the rate of reaction is also…
Correct answer: First increase then decrease in rate of reaction- A. Ionic bonds
- B. Disulphide bonds
- C. Hydrogen bond
- D. Peptide Bond
Explanation: Hydrogen bond will have affected due to increasein temperature than optimum value, while change in pH will affects ionic bond.
Correct answer: Ionic bonds- A. Peptide bonds
- B. Disulphide bridges
- C. Hydrogen bonds
- D. Ionic bonds
Explanation: Heavy metals bind to the thiol (-SH) group of amino acids and break the disulphide brides between the amino acids.
Correct answer: Disulphide bridges- A. Lyases
- B. Ligase
- C. Hydrolases
- D. None of the above
Explanation: Lyases and ligases are enzymes involved in catalyzing biochemical reactions.
Correct answer: Hydrolases- A. α-ketoglutarate
- B. Malonate
- C. Pyruvate
- D. Oxaloacetate
Explanation: Malonate or oxaloacetate resemble succinate in structure and inhibit the activity of succinate dehydrogenase.
Correct answer: Malonate- A. Increasing Temperature
- B. Decreasing pH
- C. Decreasing Activation energy
- D. Increasing Activation energy
Explanation: Minimum amount of energy required to start a biochemical reaction is called activation energy.
Correct answer: Decreasing Activation energy- A. Binding site
- B. Active site
- C. Catalyst site
- D. Inhibition site
Explanation: An enzyme and its specific substrate react with each other through a definite charge-bearing site of an enzyme called the active site.
Correct answer: Active site- A. The contact between the substrate and the enzyme causes a change in the shape of the active site
- B. The shape of the substrate and the shape of the active site are complementary to each other
- C. The substrate fits into the active site and forms bonds with the amino acids at the active site
- D. All of the above options are correct
Explanation: Options B and C are common to both lock-and-key hypothesis and induced fit model.
Correct answer: The contact between the substrate and the enzyme causes a change in the shape of the active site- A. Concentration of enzyme
- B. Concentration of substrate
- C. Concentration of ES complex
- D. Concentration of inhibitor
Explanation: Non-competitive inhibitors don't bind to the active site of the enzyme; therefore, the concentration of enzyme, substrate, or ES complex…
Correct answer: Concentration of inhibitor580. 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 allosteric site to cause a conformational shift in the enzyme
Explanation: As summed up by the diagram, the binding of noncompetitive inhibitor causes alteration in the bonding of active site, as a result…
Correct answer: Bind to allosteric site to cause a conformational shift in the enzyme