Question 1

Which of the following best explains why lipids are not considered polymers?

Accepted Answer

Lipids are made of long chains of hydrocarbons but lack a repeating monomer structure.

Question 2

A cell membrane is described as a 'fluid mosaic.' Which feature of the membrane does the term 'fluid' specifically refer to?

Accepted Answer

The ability of proteins to move laterally within the lipid bilayer.

Question 3

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

Accepted Answer

Oxygen ($$O_2)$$

Question 4

A researcher observes that a certain membrane is more permeable to water than expected. Which protein is most likely present in high amounts in this membrane?

Accepted Answer

Aquaporin

Question 5

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

Accepted Answer

They have both a hydrophilic head and a hydrophobic tail.

Question 6

How does the degree of saturation of fatty acid tails in phospholipids affect membrane fluidity at room temperature?

Accepted Answer

More unsaturated fatty acids increase membrane fluidity.

Question 7

Which of the following statements about cholesterol in animal cell membranes is correct?

Accepted Answer

Cholesterol stabilizes membrane fluidity by preventing it from becoming too rigid at low temperatures and too fluid at high temperatures.

Question 8

A red blood cell is placed in a hypotonic solution. What will happen to the cell, and why?

Accepted Answer

Water will move into the cell by osmosis, causing it to swell and possibly burst.

Question 9

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules from high to low concentration through a protein channel, without energy input.

Question 10

Which of the following would most likely decrease the permeability of a cell membrane to small, nonpolar molecules?

Accepted Answer

Increasing the length and saturation of fatty acid tails in phospholipids.

Question 11

A cell needs to import glucose against its concentration gradient. Which process will it most likely use?

Accepted Answer

Active transport using a carrier protein and ATP

Question 12

Which of the following is a real-life example of passive transport across a plasma membrane?

Accepted Answer

Oxygen diffusing from the lungs into the blood.

Question 13

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

Accepted Answer

They are hydrophilic and charged, so they cannot pass through the hydrophobic core of the bilayer.

Question 14

Which of the following best describes the role of integral membrane proteins in the plasma membrane?

Accepted Answer

They allow specific molecules to cross the membrane, changing its permeability.

Question 15

A scientist is studying two artificial membranes. Membrane A is composed of phospholipids with short, unsaturated fatty acid tails. Membrane B is composed of phospholipids with long, saturated fatty acid tails. Which membrane will be more permeable to small, nonpolar molecules, and why?

Accepted Answer

Membrane A, because short, unsaturated tails increase fluidity and permeability.

Question 16

Which of the following is true regarding osmosis?

Accepted Answer

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

Question 17

Which of the following best describes the effect of trans double bonds in fatty acids on membrane properties?

Accepted Answer

Trans double bonds make the membrane more rigid, similar to saturated fats.

Question 18

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

Accepted Answer

Storing genetic information.

Question 19

A patient is given an intravenous solution that is hypertonic relative to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

Water will leave the cells, causing them to shrink (crenate).

Question 20

Which of the following equations best represents the movement of molecules during passive transport?

Accepted Answer

$$C_{high} \rightarrow C_{low}$$

Biomolecules II: Lipids and Membranes – Structure, Properties, and Transport

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