Question

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Question 1. A reaction in an anabolic pathway in a cell has a AG of +2.5 kcal/mol. Which of the following is true regarding this reaction? A. It will occur spontaneously. B. The product of the reaction has a lower free energy than the reactants. C. It can occur if it is coupled to ATP hydrolysis. D. It is an exergonic reaction. E. It is breaking a polymer into its monomers. Question 2. Which of the following correctly characterizes the action of enzymes? A. Enzymes are consumed by the reactions they catalyze. B. Enzymes catalyze catabolic reactions only. C. Enzymes decrease the amount of energy that must be absorbed to allow a reaction to occur. D. Enzymes lower the AG of a reaction. E. All humans enzymes function best at near neutral pH. Question 3. What is the role of oxygen in aerobic cellular respiration? A. It is involved in substrate level phosphorylation. B. It accepts electrons from the oxidation of NADH. C. It oxidizes NAD to NADH. D. It reduces glucose to carbon dioxide. E. It reduces carbon dioxide to a sugar. Question 4. Which of the following is not produced in glycolysis? A. ATP B. NADH C. Pyruvate D. Carbon dioxide E. Water Question 5. Enzyme complexes of the electron transport chain move protons from the to the A. Intermembrane space, mitochondrial matrix B. Mitochondrial matrix, intermembrane space C. Cytosol, mitochondrial matrix D. Mitochondrial matrix, cytosol E. Thylakoid space, stroma

Answer 1

Question 1: Answer C

Please note in a given question, delta G is +2.5 kcal/mol. A positive value of delta G indicates that reaction is endothermic. Energy needs to be provided in the form of ATP to the reaction to occur. Therefore, C is the correct answer.

The reaction cannot occur spontaneously due to positive delta G. Reaction product will have lower free energy only if delta G is negative. Degradation of the polymer always releases the energy in the form of ATP or NADPH, and hence delta G would be negative.

Question 2: Answer C

Enzyme catalyzes the reactions by lowering the activation energy. Enzymes decrease the amount of energy requires to proceed with the reaction, which is defined as lowering the activation energy. Enzyme is not consumed during chemical reaction, neither has it undergo chemical modification. Enzyme catalyzes both, catabolic as well as anabolic reactions. The enzyme does not change the ∆G value of a given reaction. Different enzymes have different optimum pH, such as pepsin optimally functions at acidic pH (1.3), lipase (pancreas) optimally functions at pH 8.0, and trypsin optimally functions at (7.8- 8.7 ).

Question 3: Answer B

Electron transport chain plays an essential role during aerobic cellular respiration. In aerobic respiration, oxygen accepts the electron from NADH (and FADH) via a series of biochemical events. Upon acceptance of electron, water split in half and chemically combined with H+, which results in the formation of water molecules. Oxygen does not play a role in substrate levels phosphorylation. Reduction of glucose and CO2 does not occur during aerobic cellular respiration. In fact glucose oxidizes to CO2 during aerobic cellular respiration.

Question 4: Answer D and E

Glycolysis results in the formation of four ATP, two NADH, and two pyruvate molecules from one glucose molecule. Water and carbon dioxide form in a citric acid cycle, not during glycolysis.