Question 1

Which statement best describes the relationship between catabolic and anabolic pathways in cellular metabolism?

Accepted Answer

Catabolic pathways break down complex molecules to release energy, while anabolic pathways use energy to build complex molecules.

Question 2

According to the first law of thermodynamics, which of the following is true regarding energy in biological systems?

Accepted Answer

Energy may change form or be transported, but cannot be created or destroyed.

Question 3

Given the reaction: ATP + H$$_2O$$ $$ightarrow$$ ADP + P$$_i$$, with $$K_{eq} = 2.23 	imes 10^5$ at 25$$^\circ$$C, calculate the standard free energy change ($$\Delta G^\circ$$) using R = 8.31$ J/mol·K. Which is the correct value?

Accepted Answer

$$\Delta G^\circ = -30.5 kJ/$$mol

Question 4

Which equation correctly relates the standard free energy change to the equilibrium constant for a reaction?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 5

A reaction has $$\Delta G^\circ = +7.56 kJ/$$mol. What does this indicate about the direction of the reaction under standard conditions?

Accepted Answer

The reaction is endergonic and will not proceed forward spontaneously.

Question 6

Which of the following best explains why actual free energy change ($$\Delta G) $$can differ from standard free energy change ($$\Delta G^\circ) in a $$cell?

Accepted Answer

Because $$\Delta G^\circ$$ does not account for the concentrations of reactants and products in the cell.

Question 7

Which of the following is a correct application of chemical logic in biochemistry?

Accepted Answer

Electrons always move from less electronegative to more electronegative atoms in covalent bonds.

Question 8

Which of the following is NOT a common category of biochemical reactions?

Accepted Answer

Free-radical reactions are the main focus in metabolism

Question 9

In the reaction catalyzed by triose phosphate isomerase: dihydroxyacetone phosphate $$\rightarrow$$ glyceraldehyde 3-phosphate, $$K_{eq} = 0.0475 at 25$^\circC. $$Calculate $$\Delta G^\circ (in kJ/$$mol) using $$R = 8.31 J/$$mol·K.

Accepted Answer

$$\Delta G^\circ = +7.56 kJ/$$mol

Question 10

Which of the following statements about the Gibbs free energy equation is correct?

Accepted Answer

$$\Delta G = \Delta H - T \Delta S$$ describes the energy available to do work in a system.

Question 11

Which of the following best describes the role of nucleophiles in biochemical reactions?

Accepted Answer

Nucleophiles donate electron pairs to electrophiles during chemical reactions.

Question 12

Which of the following is true about the standard free energy change ($$\Delta G^\circ) $$for internal rearrangements, isomerizations, and eliminations?

Accepted Answer

These reactions tend to have small free energy changes.

Question 13

A metabolic reaction has the following concentrations: [Glucose] = 5 mM, [ATP] = 0.1 mM, [Glucose-6-P] = 80 mM, [ADP] = 1.2 mM. If $$\Delta G^\circ = -16.7 kJ/$$mol, calculate the actual free energy change ($$\Delta G) at 25$^\circC $$using $$\Delta G = \Delta G^\circ + RT \ln \frac{[Glucose-6-P][ADP]}{[Glucose][ATP]}$$ and $$R = 8.314 J/$$mol·K.

Accepted Answer

$$\Delta G = +0.5 kJ/$$mol

Question 14

Which of the following is a correct statement about the spontaneity of a reaction?

Accepted Answer

A reaction is spontaneous if $$\Delta G \u003c 0.$$

Question 15

Which of the following is a real-life example of a group transfer reaction in metabolism?

Accepted Answer

Phosphorylation of glucose by ATP to form glucose-6-phosphate.

Question 16

Which physical constant is correctly matched with its value?

Accepted Answer

Avogadro's number, $$N = 6.022 	imes 10$$^{23}$$ mol$$^{-1}$$

Question 17

Which of the following best describes the function of carbonyl groups in biochemical reactions?

Accepted Answer

Carbonyl groups act as electrophiles, facilitating nucleophilic attack.

Question 18

Which of the following metabolic reactions is an example of a Claisen ester condensation?

Accepted Answer

Formation of acetoacetyl-CoA from two acetyl-CoA molecules in fatty acid synthesis.

Question 19

Which of the following statements about metabolic pathways is correct?

Accepted Answer

Metabolic pathways can converge, diverge, or cycle.

MCB 102: Metabolism – Bioenergetics and Chemical Logic Study Notes

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