Question 1

Which of the following best explains why the hydrolysis of ATP to ADP and inorganic phosphate ($$P_i) is $$highly exergonic under cellular conditions?

Accepted Answer

Because the products (ADP and $$P_i) $$are stabilized by resonance and have increased entropy compared to ATP.

Question 2

A red blood cell is placed in a solution containing 0.25 M sucrose. The cell begins to swell and eventually bursts. Which of the following best explains this observation?

Accepted Answer

The cell has sucrose carrier proteins, allowing sucrose to enter and increase internal osmolarity, drawing in water.

Question 3

Which of the following statements about the Na$$^+/K$^+$$ pump (Na/K ATPase) is CORRECT?

Accepted Answer

It moves three Na$$^+$$ ions out of the cell and two K$$^+$$ ions into the cell per ATP hydrolyzed.

Question 4

A patient is given a drug that specifically inhibits the Na$$^+/K$^+$$ ATPase. Which of the following processes would be most directly affected in intestinal epithelial cells?

Accepted Answer

Active transport of glucose into the cell via the Na$$^+/$$glucose symporter.

Question 5

Which of the following equations correctly describes the free energy change ($$\Delta G) $$for the inward transport of an uncharged solute S from outside to inside the cell?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[S]_{in}}{[S]_{out}} \right)$$

Question 6

A cell is exposed to a toxin that makes its inner mitochondrial membrane highly permeable to protons. What is the most immediate effect on cellular respiration?

Accepted Answer

Electron transport and oxygen consumption will continue, but ATP synthesis will decrease dramatically.

Question 7

Which of the following best describes the role of coenzyme Q (ubiquinone) in the mitochondrial electron transport chain?

Accepted Answer

It acts as a mobile electron and proton carrier within the inner mitochondrial membrane.

Question 8

A plant mutant is found to have a defective triose phosphate/phosphate translocator in the chloroplast inner membrane. Which of the following is a likely consequence?

Accepted Answer

The plant will be unable to export triose phosphates to the cytosol for sucrose synthesis.

Question 9

Which of the following statements about the Calvin cycle is TRUE?

Accepted Answer

It requires both ATP and NADPH to reduce 3-phosphoglycerate to glyceraldehyde-3-phosphate.

Question 10

Which of the following best explains why C$$_4$$ plants are more efficient than C$$_3$$ plants in hot, arid environments?

Accepted Answer

C$$_4$$ plants spatially separate initial CO$$_2$$ fixation from the Calvin cycle, concentrating CO$$_2$$ around rubisco and minimizing photorespiration.

Question 11

Which of the following is a key difference between simple diffusion and facilitated diffusion across biological membranes?

Accepted Answer

Facilitated diffusion exhibits saturation kinetics due to the limited number of transport proteins.

Question 12

A researcher measures the rate of glucose uptake in erythrocytes and finds that it follows a hyperbolic curve when plotted against external glucose concentration. What does this suggest about the transport mechanism?

Accepted Answer

Glucose is transported by a carrier protein exhibiting saturation kinetics.

Question 13

Which of the following best describes the function of the oxygen-evolving complex in photosystem II?

Accepted Answer

It catalyzes the splitting of water to provide electrons for P680 and releases O$$_2 as a $$byproduct.

Question 14

Which of the following is a direct result of cyclic electron flow around photosystem I in chloroplasts?

Accepted Answer

ATP is synthesized without the production of NADPH or O$$_2.$$

Question 15

Which of the following best explains why the actual ATP yield from aerobic respiration in eukaryotic cells is often less than the theoretical maximum of 38 ATP per glucose?

Accepted Answer

Some of the proton gradient is used for other transport processes and the inner mitochondrial membrane is slightly leaky to protons.

Question 16

A mutation in a plant prevents the reduction of ferredoxin in the chloroplast. Which process would be most directly impaired?

Accepted Answer

The reduction of NADP$$^+ to $$NADPH during the light reactions.

Question 17

Which of the following statements about the binding change model of ATP synthesis by $$F_1F_0-$$ATP synthase is CORRECT?

Accepted Answer

Rotation of the gamma ($$\gamma) $$subunit induces conformational changes in the $$\beta$$ subunits, cycling them through open, loose, and tight states.

Question 18

Which of the following best describes the effect of high concentrations of ATP on the activity of phosphofructokinase-1 (PFK-1) in glycolysis?

Accepted Answer

ATP acts as an allosteric inhibitor, decreasing the enzyme's activity.

Question 19

Which of the following is a key regulatory mechanism that prevents futile cycling between glycolysis and gluconeogenesis in liver cells?

Accepted Answer

Reciprocal allosteric regulation of key enzymes by metabolites such as AMP, ATP, and fructose-2,6-bisphosphate.

Cell Biology Study Guide: Membrane Transport, Glycolysis, Aerobic Respiration, and Photosynthesis

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