Question 1

Which of the following best describes the primary function of the plasma membrane in both prokaryotic and eukaryotic cells?

Accepted Answer

It serves as a selective barrier, allowing the internal composition of the cell to differ from the external environment.

Question 2

A bacterium from the Arctic Circle is ingested by an animal and must survive in the animal's warmer intestine. To maintain the same membrane fluidity, which adjustment should the bacterium make to its membrane lipids?

Accepted Answer

Increase the proportion of saturated fatty acid tails in its membrane lipids.

Question 3

Which of the following statements about membrane fluidity is CORRECT?

Accepted Answer

Shorter hydrocarbon tails increase membrane fluidity.

Question 4

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

The hydrophilic heads interact with water, while the hydrophobic tails avoid water, leading to bilayer formation.

Question 5

A mutation in the spectrin gene in red blood cells (RBCs) can lead to which of the following clinical outcomes?

Accepted Answer

Abnormally shaped, spherical RBCs and anemia due to membrane instability.

Question 6

Which of the following is a function of glycoproteins and glycolipids on the extracellular surface of eukaryotic plasma membranes?

Accepted Answer

They form the glycocalyx, which protects the cell and mediates cell-cell recognition.

Question 7

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

Cholesterol fills spaces between phospholipids, making the membrane less permeable and more rigid.

Question 8

Which of the following is TRUE regarding the asymmetry of the plasma membrane?

Accepted Answer

The cytosolic and non-cytosolic leaflets of the membrane have distinct lipid compositions that are maintained during vesicle transport.

Question 9

Which of the following best describes a transmembrane protein?

Accepted Answer

A protein that spans the lipid bilayer with hydrophobic regions interacting with the membrane interior.

Question 10

Which of the following is a plausible consequence if a cell membrane becomes too fluid at high temperatures?

Accepted Answer

The membrane may become leaky, allowing uncontrolled movement of substances across it.

Question 11

Which of the following best explains why flip-flop movement of phospholipids between leaflets of the bilayer is rare?

Accepted Answer

It requires the passage of hydrophilic head groups through the hydrophobic core, which is energetically unfavorable.

Question 12

Which of the following is an example of a multipass transmembrane protein and its function?

Accepted Answer

Na	extsuperscript{+} pump; actively transports Na	extsuperscript{+} out of the cell.

Question 13

Which of the following best describes the effect of unsaturated fatty acid tails on membrane fluidity?

Accepted Answer

They introduce kinks that prevent tight packing, increasing fluidity.

Question 14

A scientist treats a cell membrane with a strong detergent. Which of the following is most likely to occur?

Accepted Answer

Integral membrane proteins will be released from the membrane.

Question 15

Which of the following best explains the role of tight junctions in epithelial cells?

Accepted Answer

They restrict the movement of membrane proteins, maintaining distinct domains on the cell surface.

Question 16

Which of the following is a real-life example of the importance of cell-surface carbohydrates in human health?

Accepted Answer

They allow immune cells to recognize and migrate to sites of infection.

Question 17

Which of the following equations best represents the relationship between the number of double bonds ($$n) in $$fatty acid tails and the membrane fluidity ($$F$$), assuming all other factors are constant?

Accepted Answer

$$F \propto n$$

Question 18

Which of the following best describes the function of integrins in the plasma membrane?

Accepted Answer

They link intracellular actin filaments to extracellular matrix proteins.

Question 19

Which of the following is a correct statement about the movement of phospholipids in the membrane?

Accepted Answer

Phospholipids can rotate, flex, and move laterally within the same leaflet.

Question 20

Which of the following best explains why the formation of a sealed phospholipid bilayer is energetically favorable?

Accepted Answer

It shields hydrophobic tails from water, minimizing unfavorable interactions.

Membrane Structure and Function: Cell Biology Study Notes

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