Q: A scientist is studying a reaction with $$\Delta H = -200 kJ/$$mol and $$\Delta S = +0.5 kJ/($$mol·K)$$. At T = 300$ K, what is the value of $$\Delta G$ and is the reaction spontaneous?

$$\Delta G = -200 - (300 \times 0.5) = -200 - 150 = -350 kJ/$$mol; the reaction is spontaneous.

Question 1

Which of the following statements best explains why only reactions with a negative $$\Delta G$$ are considered spontaneous in biological systems?

Accepted Answer

Because a negative $$\Delta G$$ means the reaction releases free energy, making it energetically favorable.

Question 2

A scientist is studying a reaction with $$\Delta H = -200 kJ/$$mol and $$\Delta S = +0.5 kJ/($$mol·K)$$. At T = 300$ K, what is the value of $$\Delta G$ and is the reaction spontaneous?

Accepted Answer

$$\Delta G = -200 - (300 	imes 0.5) = -200 - 150 = -350 kJ/$$mol; the reaction is spontaneous.

Question 3

Which of the following best describes the role of ATP in cellular metabolism?

Accepted Answer

ATP couples exergonic and endergonic reactions by providing energy for cellular work.

Question 4

During the hydrolysis of ATP, which of the following occurs?

Accepted Answer

A phosphate group is removed from ATP, forming ADP and releasing energy.

Question 5

Which of the following equations correctly represents the relationship between free energy, enthalpy, and entropy?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 6

A glow-in-the-dark necklace emits light after being snapped, causing a chemical reaction. This reaction is best described as:

Accepted Answer

Exergonic, because it releases energy in the form of light.

Question 7

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy barrier, allowing reactions to proceed faster.

Question 8

A patient has a genetic mutation that causes their enzymes to denature at 37°C, rather than the normal 40°C. What is the most likely effect on their metabolism at normal body temperature?

Accepted Answer

Their metabolic reactions will slow down due to loss of enzyme activity.

Question 9

Which of the following best explains why enzymes are specific to their substrates?

Accepted Answer

The active site of an enzyme has a unique shape and chemical environment that matches only specific substrates.

Question 10

Which of the following is true regarding the difference between aerobic respiration and fermentation?

Accepted Answer

Aerobic respiration produces more ATP per glucose molecule than fermentation.

Question 11

In the following redox reaction, which compound is oxidized and which is reduced? $$C_6H_{12}O_6$ + NAD^+ \rightarrow 6CO_2 + NADH + H^+$$

Accepted Answer

$$C_6H_{12}O_6$ is oxidized; $$NAD^+$$ is reduced.

Question 12

Which of the following best describes substrate-level phosphorylation?

Accepted Answer

ATP is produced directly by transferring a phosphate group from an organic substrate to ADP.

Question 13

During strenuous exercise, muscle cells switch to lactic acid fermentation. What is the primary purpose of this metabolic shift?

Accepted Answer

To regenerate NAD$$^+ so $$glycolysis can continue in the absence of oxygen.

Question 14

Which of the following statements about the electron transport chain in cellular respiration is correct?

Accepted Answer

It transfers electrons from NADH to oxygen, releasing energy used to pump protons and drive ATP synthesis.

Question 15

A yeast cell is moved from an aerobic to an anaerobic environment. If it must maintain the same rate of ATP production, what will happen to its rate of glucose consumption?

Accepted Answer

It will increase because fermentation yields less ATP per glucose.

Question 16

Which of the following is a correct statement about the ATP cycle in cells?

Accepted Answer

ATP is regenerated from ADP and inorganic phosphate using energy from exergonic reactions.

Question 17

Which of the following best explains why enzymes do not alter the $$\Delta G of a $$reaction?

Accepted Answer

Enzymes only lower the activation energy, not the overall free energy change.

Question 18

Which of the following environmental changes is most likely to decrease the rate of an enzyme-catalyzed reaction in the human body?

Accepted Answer

Decreasing the pH from 7.4 to 2 for an enzyme with optimal pH 7.4.

Question 19

Which of the following best describes the fate of the energy released from glucose during cellular respiration?

Accepted Answer

Some is stored as ATP, and the rest is released as heat.

Section 5: Metabolism – Energy, Enzymes, and Cellular Respiration

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