Question 1

Which of the following best explains why winter wheat maintains membrane fluidity during cold temperatures?

Accepted Answer

It increases the proportion of unsaturated fatty acids, preventing the membrane from solidifying.

Question 2

A cell is placed in a hypertonic solution. Which process is most likely to occur, and what is the expected outcome for a plant cell?

Accepted Answer

Osmosis; the cell will lose water and undergo plasmolysis.

Question 3

Which equation correctly represents the ATP hydrolysis reaction that powers the sodium-potassium pump?

Accepted Answer

$$\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i}$$

Question 4

Which of the following statements about integral and peripheral membrane proteins is correct?

Accepted Answer

Integral proteins penetrate the hydrophobic interior of the membrane and can act as channels or receptors.

Question 5

A cell uses a proton-sucrose co-transporter to import sucrose. Which of the following best describes the energy requirements and mechanism?

Accepted Answer

Sucrose is imported along with H$$^+$$, using the energy of the H$$^+$$ gradient established by a proton pump.

Question 6

Which process is responsible for the rapid release of adrenaline from the adrenal medulla during a 'fight-or-flight' response?

Accepted Answer

Bulk exocytosis

Question 7

Which of the following molecules can cross the plasma membrane by simple diffusion without the aid of proteins?

Accepted Answer

O$$_2$$

Question 8

A cell is actively exporting Na$$^+$$ ions and importing K$$^+$$ ions. Which transport mechanism is being used, and what is the stoichiometry per cycle?

Accepted Answer

Active transport; 3 Na$$^+$$ out, 2 K$$^+ in$$

Question 9

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

It requires a ligand to bind to a cell-surface receptor, triggering vesicle formation.

Question 10

Which scenario illustrates the difference between bulk exocytosis and single-molecule secretion?

Accepted Answer

Bulk exocytosis releases large quantities of hormones rapidly, while single-molecule secretion releases neurotransmitters slowly and continuously.

Question 11

Which of the following is TRUE regarding the effect of cholesterol on membrane fluidity?

Accepted Answer

Cholesterol decreases membrane fluidity at moderate temperatures and prevents solidification at low temperatures.

Question 12

Which process is most likely to be used by a macrophage to engulf and digest a bacterium?

Accepted Answer

Phagocytosis

Question 13

A plant cell in a hypotonic environment will:

Accepted Answer

Gain water and become turgid.

Question 14

Which of the following best describes facilitated diffusion?

Accepted Answer

It uses channel or carrier proteins to move molecules down their concentration gradient without energy input.

Question 15

Which equation best represents the movement of water across a membrane via osmosis?

Accepted Answer

$$\mathrm{H_2O}$$ moves from an area of low solute concentration to high solute concentration through aquaporins.

Question 16

Which of the following is a key difference between phagocytosis and pinocytosis?

Accepted Answer

Phagocytosis engulfs large particles, while pinocytosis internalizes small droplets of extracellular fluid.

Question 17

Which of the following statements about membrane transport is correct?

Accepted Answer

Passive transport includes simple diffusion and facilitated diffusion, both moving molecules down their concentration gradient.

Question 18

A cell needs to import glucose, which is a large, polar molecule. Which transport mechanism is most likely used?

Accepted Answer

Facilitated diffusion via a carrier protein

Question 19

Which of the following best describes the role of SNARE proteins in exocytosis?

Accepted Answer

They mediate vesicle–membrane fusion, allowing contents to be released.

CHAPTER 5

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