This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Bioenergetics”.
1. Reactions that lose heat are termed as _____________
Explanation: Energy can neither be created nor be destroyed. It is only transduced from one form into another. Heat is also a form of energy; reactions in which heat is lost to the surroundings are termed as exothermic reactions and those in which heat is gained from the system are termed as endothermic reactions.
2. According to laws of thermodynamics, the energy of the Universe is _________ whereas the entropy ______________
a) constant, increases
b) constant, decreases
c) increases, remains constant
d) decreases, remains constant
Explanation: According to the first and second laws of thermodynamics, the energy of the universe remains constant however the entropy increases owing to the randomness.
3. Exergonic processes are thermodynamically unfavorable.
Explanation: The processes having negative Gibbs free energy (-ΔG) are termed as exergonic; are thermodynamically favored and are spontaneous in nature. Processes having +ΔG are endergonic, thermodynamically unfavorable and non-spontaneous.
4. Hydrolysis of ATP is which type of reaction?
Explanation: Hydrolysis of ATP is the most important chemical reaction in a living cell. It is highly favorable and exergonic with a standard free energy (ΔG⁰’) between reactants and products equal to -7.3 kcal/mol.
5. Cellular metabolism is a non-equilibrium metabolism.
Explanation: Cellular metabolism is essentially a non-equilibrium metabolism; that is the ratio of reactants to products is maintained in a non-equilibrium state. This makes most of the reactions irreversible.
6. Which of the following are responsible virtually for every reaction that takes place inside a cell?
c) Nucleic acids
Explanation: Enzymes are the catalysts responsible for virtually everything that takes place inside a cell. Without these catalysts the cellular metabolism and bioenergetics would be imperceptible.
7. Protein catalysts are called __________ and RNA catalysts are called _____________
a) enzymes, ribozymes
b) ribozymes, enzymes
c) enzymes, ribosomes
d) ribosomes, enzymes
Explanation: RNA catalysts are called ribozymes whereas protein catalysts are called enzymes. Most of the catalysts are enzymes made of proteins.
8. The non-protein constituents of conjugated proteins are called ___________
c) amino acids
Explanation: The non-protein constituents of conjugated proteins (that act as enzymes) are called cofactors. These cofactors can be inorganic metals or organic coenzymes.
9. Enzymes have no effect on which of the following, in a chemical reaction?
a) activation energy
d) completion time
Explanation: Enzymes are responsible for catalyzing reactions by reducing the activation energy. However there is no effect on the thermodynamic aspect of the given reaction.
10. What will happen if heat is applied to an enzyme mediated reaction?
a) Rate will increase
b) pH will increase
c) pH will decrease
d) Denaturation of enzyme
Explanation: The rate of an enzymatic reaction will increase with temperature but only upto a certain limit. Too much heat energy causes the enzyme to denature. This rate varies among different enzymes.
11. Chymotrypsin is a ___________
Explanation: Chymotrypsin is an enzyme that digests food proteins within the small intestine. The active site of this enzyme contains partial positive and partial negative charges.
12. Induced fit in an enzyme refers to ____________________
c) conformational change
d) torsional change
Explanation: Induced fit of an enzyme refers to the conformational change that arises when a substrate molecule comes and binds to an enzyme. As these conformational changes arise, mechanical work is performed the enzyme exerts physical force on certain bonds within the substrate. This has an effect of destabilizing the enzyme, causing it to adopt a transition state in which this strain is relieved.
13. Allosteric site is same as enzyme’s active site.
Explanation: Allosteric site is spatially different from enzyme’s active site. It is the site where a compound can bind and lead to inhibition or activation of an enzyme.
14. Feedback inhibition is cell’s mechanism to _____________ the process of anabolism.
Explanation: Feedback inhibition acts as a check point. If the formation of products is too much, the product itself acts as the inhibitor of the enzyme thus causing the reaction to stop. Feedback inhibition loop is found in most of the cell’s anabolic and catabolic processes.
15. What is the process of synthesis of glucose by the liver is referred to as?
Explanation: The anabolic pathway that leads to the formation of glucose is referred to as gluconeogenesis. A cell can synthesize glucose at the same it is utilizing glucose as the source of chemical energy.
Sanfoundry Global Education & Learning Series – Cell Biology.
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