Question 1

A researcher is studying the movement of a small, uncharged, hydrophobic molecule across a cell membrane. Which of the following best describes how this molecule will cross the membrane?

Accepted Answer

It will diffuse directly through the lipid bilayer without the need for a protein or energy input.

Question 2

Which of the following statements correctly distinguishes between channels and pumps in membrane transport?

Accepted Answer

Channels allow substances to move down their concentration gradient without energy input, while pumps use ATP to move substances against their gradient.

Question 3

A cell is placed in a solution where the concentration of solute is higher outside the cell than inside. What will happen to the water movement across the membrane?

Accepted Answer

Water will move out of the cell by osmosis.

Question 4

Which of the following best explains why the Na+/K+ ATPase pump is important for secondary active transport in animal cells?

Accepted Answer

It establishes a sodium gradient that can be used by transporters to move other substances against their concentration gradients.

Question 5

A hydrophobic signaling molecule is released into the bloodstream. Where would you expect to find its receptor?

Accepted Answer

Inside the cytoplasm or nucleus of the target cell.

Question 6

Which of the following correctly orders the stages of cellular signaling?

Accepted Answer

Reception → Signal transduction → Response

Question 7

A mutation causes an enzyme’s active site to change shape. What is the most likely consequence for the enzyme’s function?

Accepted Answer

The enzyme may no longer bind its substrate effectively, reducing or eliminating its catalytic activity.

Question 8

Which of the following statements about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy of a reaction but do not change the overall $$\Delta G.$$

Question 9

A reaction has a $$\Delta G = +5$$ kcal/mol. Which of the following is true about this reaction?

Accepted Answer

It is endergonic and will not occur spontaneously unless coupled to an exergonic reaction.

Question 10

Which of the following best describes how ATP hydrolysis is used to drive endergonic reactions in cells?

Accepted Answer

ATP hydrolysis is coupled to endergonic reactions, often by transferring a phosphate group to a reactant, making the overall $$\Delta G$$ negative.

Question 11

A scientist blocks the electron transport chain in a eukaryotic cell. What is the most immediate effect on cellular respiration?

Accepted Answer

The citric acid cycle will eventually stop due to a lack of NAD+ and FAD.

Question 12

During aerobic cellular respiration, where do the oxygen atoms in the carbon dioxide ($$\mathrm{CO_2$}) $$produced come from?

Accepted Answer

From the glucose molecule being broken down.

Question 13

Which of the following is a correct comparison between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus containing their DNA, while prokaryotic cells do not.

Question 14

A plant cell is observed to have an unusually high number of chloroplasts. What is the most likely function of this cell?

Accepted Answer

Photosynthesis

Question 15

Which of the following best explains why a spontaneous reaction (negative $$\Delta G) $$may not occur rapidly in a cell?

Accepted Answer

The activation energy barrier is too high for the reaction to proceed quickly.

Question 16

A cell is exposed to a toxin that specifically inhibits phosphorylation events in signal transduction pathways. Which of the following is a likely consequence?

Accepted Answer

Signal transduction will be impaired, and the cell may not respond appropriately to external signals.

Question 17

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the diffusion of water across a selectively permeable membrane.

Question 18

If a cell’s environment becomes much more acidic than its normal conditions, what is the most likely effect on its enzymes?

Accepted Answer

Enzyme activity will decrease because the enzyme’s shape and function are optimized for its normal environment.

Question 19

A patient is found to have high levels of pyruvate in their cells. Which of the following is the most likely explanation?

Accepted Answer

The transition reaction (pyruvate to acetyl-CoA) is impaired, causing pyruvate to accumulate.

UCSD BILD 1: The Cell - Exam 2 Study Guide

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