Question 1

Which of the following best describes how enzymes affect the activation energy of a chemical reaction?

Accepted Answer

Enzymes lower the activation energy, allowing reactions to proceed more rapidly at biological temperatures.

Question 2

A scientist observes that an enzyme-catalyzed reaction rate decreases sharply when the pH is changed from 7 to 3. What is the most likely explanation for this observation?

Accepted Answer

The enzyme denatures due to the acidic environment, altering its active site.

Question 3

Which equation correctly represents the Gibbs Free Energy change ($\Delta G$) for a chemical reaction?

Accepted Answer

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

Question 4

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the active site, preventing substrate binding.

Question 5

During cellular respiration, which organelle is primarily responsible for ATP production in eukaryotic cells?

Accepted Answer

Mitochondrion

Question 6

Which of the following statements about the effect of temperature on enzyme activity is correct?

Accepted Answer

Enzyme activity increases with temperature up to an optimal point, then decreases due to denaturation.

Question 7

Which process occurs in the stroma of the chloroplast?

Accepted Answer

The Calvin cycle (light-independent reactions)

Question 8

If a protein is denatured by heat, which of the following best describes what happens to its function?

Accepted Answer

The protein loses its specific shape and cannot function properly.

Question 9

Which of the following is a product of the light-dependent reactions of photosynthesis?

Accepted Answer

ATP

Question 10

A noncompetitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to an allosteric site, changing the enzyme's shape and reducing activity.

Question 11

Which of the following statements about glycolysis is TRUE?

Accepted Answer

Glycolysis is performed by all living organisms.

Question 12

Which of the following best explains why living organisms require a constant input of energy?

Accepted Answer

To maintain order and power cellular processes, as required by the laws of thermodynamics.

Question 13

Which of the following is a direct result of energy coupling in cellular metabolism?

Accepted Answer

Exergonic reactions drive endergonic reactions, allowing cells to perform work.

Question 14

Which of the following is the correct sequence for the flow of electrons during the light-dependent reactions of photosynthesis?

Accepted Answer

Water $\rightarrow$ Photosystem II $\rightarrow$ Photosystem I $\rightarrow$ NADPH

Question 15

A mutation causes an enzyme's active site to change shape. What is the most likely effect on the enzyme's function?

Accepted Answer

The enzyme may lose its ability to bind substrates, reducing or eliminating its activity.

Question 16

Which of the following statements about the second law of thermodynamics is correct in the context of living systems?

Accepted Answer

Living systems maintain order by increasing entropy in their surroundings.

Question 17

Which of the following is a key structural feature of the chloroplast that allows for efficient photosynthesis?

Accepted Answer

Stacked thylakoid membranes (grana) to maximize light absorption.

Question 18

Which of the following is TRUE regarding oxidative phosphorylation?

Accepted Answer

It is conserved across all domains: Archaea, Bacteria, and Eukarya.

Question 19

A student adds more substrate to an enzyme-catalyzed reaction and observes that the reaction rate increases, then levels off. What is the most likely explanation for this observation?

Accepted Answer

All enzyme active sites are saturated, so adding more substrate does not increase the rate further.

Question 20

Which of the following best describes the role of NADPH in photosynthesis?

Accepted Answer

NADPH acts as an electron donor in the Calvin cycle, helping to reduce carbon dioxide to glucose.

General Biology Study Guide: Enzymes, Cellular Energy, Photosynthesis, and Cellular Respiration

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