Question 1

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have both a hydrophilic head and a hydrophobic tail.

Question 2

Why do phospholipids spontaneously form bilayers in aqueous solutions?

Accepted Answer

Because their hydrophilic heads interact with water while their hydrophobic tails avoid water.

Question 3

Which of the following molecules would most easily cross a pure phospholipid bilayer?

Accepted Answer

O$$_2$$

Question 4

How does the presence of unsaturated fatty acid chains in phospholipids affect membrane permeability?

Accepted Answer

It increases permeability by preventing tight packing of the tails.

Question 5

A red blood cell is placed in a hypertonic solution. What will happen to the cell?

Accepted Answer

Water will leave the cell, causing it to shrink.

Question 6

Which of the following best explains why cholesterol decreases membrane permeability to small molecules?

Accepted Answer

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

Question 7

Which process requires energy input from ATP to move substances across the membrane?

Accepted Answer

Active transport

Question 8

The sodium-potassium pump (Na$$^+/K$^+-$$ATPase) moves:

Accepted Answer

3 Na$$^+$$ out of the cell and 2 K$$^+$$ into the cell per ATP hydrolyzed.

Question 9

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It requires a membrane protein and moves substances down their concentration gradient.

Question 10

A cell is placed in a solution and swells until it bursts. The solution is:

Accepted Answer

Hypotonic relative to the cell.

Question 11

Which of the following best describes the fluid mosaic model of membrane structure?

Accepted Answer

A dynamic arrangement of phospholipids and proteins that move laterally within the layer.

Question 12

Which of the following is an example of bulk transport across the plasma membrane?

Accepted Answer

Endocytosis

Question 13

If the temperature of a membrane increases above its melting temperature ($$T_m$$), what happens to its permeability?

Accepted Answer

Permeability increases due to increased molecular motion.

Question 14

Which of the following best explains why ions such as Na$$^+$$ and K$$^+$$ cannot easily cross the phospholipid bilayer?

Accepted Answer

They are charged and cannot pass through the hydrophobic core of the bilayer.

Question 15

Which of the following scenarios best illustrates secondary active transport?

Accepted Answer

A glucose molecule is transported into a cell using the energy stored in a Na$$^+$$ gradient.

Question 16

Which of the following would most likely increase the fluidity of a cell membrane?

Accepted Answer

Increasing the proportion of unsaturated fatty acids.

Question 17

Which of the following is true about osmosis?

Accepted Answer

Water moves from areas of low solute concentration to areas of high solute concentration.

Question 18

A mutation causes a cell to lack aquaporins. What is the most likely effect?

Accepted Answer

The cell will have reduced water permeability.

Question 19

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Synthesizing phospholipids.

Question 20

Which of the following best describes the effect of adding cholesterol to a membrane at low temperatures?

Accepted Answer

It increases membrane fluidity by preventing tight packing of phospholipids.

Membrane Structure and Transport: General Biology Study Notes

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