Cell Biology Multiple Choice Questions on “Bioenergetics”.
1. Reactions that lose heat are termed as _____________
A. endothermic
B. exothermic
C. chemical
D. physical
Answer: B
Clarification: 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
Answer: A
Clarification: 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.
A. True
B. False
Answer: B
Clarification: 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?
A. Physical
B. Mechanical
C. Endergonic
D. Exergonic
Answer: D
Clarification: 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.
A. True
B. False
Answer: A
Clarification: 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?
A. Carbohydrates
B. ADP
C. Nucleic acids
D. Enzymes
Answer: A
Clarification: 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
Answer: A
Clarification: 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 ___________
A. enzymes
B. cofactors
C. amino acids
D. nucleosides
Answer: B
Clarification: 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
B. speed
C. thermodynamics
D. completion time
Answer: C
Clarification: 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