This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Enzymes – 1”.
1. A __________is a biocatalyst that increases the rate of the reaction without being changed.
a) Aluminum oxide
b) Silicon dioxide
d) Hydrogen peroxide
Explanation: Among these options, an enzyme is an only option which is a biocatalyst that catalyzes the chemical reaction without being changed while all other options are of the catalyst which increases or decrease the rate of reaction based on their concentration.
2. Enzyme increases the rate of reaction by lowering the activation energy.
Explanation: Activation energy is the difference in free energy between the reactants and transition state. To complete a reaction, enzyme lowers the activation energy and crosses the transition state.
3. What is the nature of an enzyme?
Explanation: All enzymes are protein except Catalytic RNA molecule. The native protein conformation of an enzyme defines its catalytic activity. Once the enzyme is denatured, its catalytic activity is also lost.
4. What is an apoenzyme?
a) It is a protein portion of an enzyme
b) It is a non-protein group
c) It is a complete, biologically active conjugated enzyme
d) It is a prosthetic group
Explanation: Removal of cofactor from a conjugated enzymes forms apoenzyme which is a protein component. A cofactor is a non-protein group while a complete conjugated enzyme is known as a holoenzyme.
5. Name the coenzyme of riboflavin (B2)?
a) NAD or NADP
b) FAD and FMN
c) Coenzyme A
d) Thiamine pyrophosphate
Explanation: Riboflavin is a part of vitamin B complex, its coenzyme form is a FAD (Flavin adenine dinucleotide) which involves a redox reaction. NAD is a coenzyme form of nicotinic acid, and thiamine pyrophosphate is a coenzyme of thiamine.
6. Which of this vitamin is associated with the coenzyme Biocytin?
a) Nicotinic acid
Explanation: Biocytin is a coenzyme of biotin which involves in carboxylation reaction while thiamine takes part in decarboxylation reaction.
7. Name the enzyme secreted by pancreas?
d) Alcohol dehydrogenase
Explanation: Trypsin is a proteolytic enzyme, secreted by the pancreas. It is one of the three digestive proteinases along with pepsin and chymotrypsin which breaks down dietary protein molecules into simpler forms.
8. Name the enzyme which catalyzes the oxidation-reduction reaction?
b) Glutamine synthetase
Explanation: Oxidoreductase is a class of enzyme which catalyze the oxidation-reduction reaction. Some of the oxidoreductase enzymes are oxidases, dehydrogenases, peroxidases etc.
9. What is the function of phosphorylase?
a) Transfer inorganic phosphate
b) Transfer a carboxylate group
c) Use H2O2 as the electron acceptor
d) Transfer amino group
Explanation: Phosphorylase is a transferase enzyme which involves a transfer of inorganic phosphate to a substrate while transcarboxylase transfer a carboxylate group and transaminase transfer amino group from amino acid to the keto acid.
10. Mark the CORRECT function of enzyme, Peptidase?
a) Cleave phosphodiester bond
b) Cleave amino bonds
c) Remove phosphate from a substrate
d) Removal of H2O
Explanation: Hydrolases are the enzymes which cleave the bond by adding water. Peptidases belong to hydrolase class and it is used to cleave amide bonds of proteins.
11. Which of the following reaction is catalyzed by Lyase?
a) Breaking of bonds
b) Formation of bonds
c) Intramolecular rearrangement of bonds
d) Transfer of group from one molecule to another
Explanation: Lyase is the class of enzymes which does not involve hydrolysis or oxidation to break the bond. It catalyzes the breaking of C-C, C-O, C-N, C-S bonds by the process of elimination and results in the formation of a double bond.
Sanfoundry Global Education & Learning Series – Life Sciences.
To practice all areas of Life Sciences, here is complete set of 1000+ Multiple Choice Questions and Answers.