Question 1

Which of the following best describes the structure of a phospholipid in the plasma membrane?

Accepted Answer

A molecule with a polar phosphate head and two hydrophobic hydrocarbon tails.

Question 2

Which property of phospholipids is most responsible for the formation of the lipid bilayer in cell membranes?

Accepted Answer

Their amphipathic nature, having both hydrophilic and hydrophobic regions.

Question 3

A patient is found to have rigid cell membranes that do not function properly. Which of the following changes in membrane composition is most likely responsible?

Accepted Answer

Increased proportion of saturated fatty acids.

Question 4

Which of the following molecules can pass directly through the plasma membrane without the aid of a transport protein?

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 5

Which equation best represents the formation of a fat (triacylglycerol) from its components?

Accepted Answer

$$\mathrm{Glycerol} + 3\ \mathrm{Fatty\ acids} \longrightarrow \mathrm{Triacylglycerol} + 3\ \mathrm{H_2O}$$

Question 6

Which of the following best explains why unsaturated fats are liquid at room temperature?

Accepted Answer

Their hydrocarbon chains contain double bonds, causing kinks that prevent tight packing.

Question 7

A cell is placed in a solution with a higher concentration of solutes than inside the cell. Which process will most likely occur?

Accepted Answer

Water will move out of the cell by osmosis.

Question 8

Which of the following is NOT a function of steroids in biological systems?

Accepted Answer

Storing energy for long-term use.

Question 9

Which factor would most likely increase the fluidity of a cell’s plasma membrane?

Accepted Answer

Increasing the proportion of unsaturated fatty acids.

Question 10

Which of the following statements about membrane transport is correct?

Accepted Answer

Bulk transport involves the movement of large molecules via vesicles.

Question 11

A researcher observes that a cell is able to take in large particles from its environment. Which transport mechanism is most likely responsible?

Accepted Answer

Endocytosis

Question 12

Which of the following best describes the difference between saturated and unsaturated fatty acids?

Accepted Answer

Unsaturated fatty acids have double bonds in their hydrocarbon chains; saturated do not.

Question 13

Which of the following is a correct statement about the selective permeability of the plasma membrane?

Accepted Answer

Only small hydrophobic molecules can pass directly through the membrane.

Question 14

Which of the following is a function of cholesterol in the plasma membrane?

Accepted Answer

It stabilizes membrane fluidity by preventing extremes of rigidity or fluidity.

Question 15

A cell is observed to have a high rate of ATP consumption during the transport of sodium ions. Which transport mechanism is most likely being used?

Accepted Answer

Active transport

Question 16

Which of the following best describes the role of phospholipids in biological membranes?

Accepted Answer

They form a bilayer that creates a semi-permeable barrier.

Question 17

Which of the following is a correct example of bulk transport in cells?

Accepted Answer

Endocytosis of bacteria by a white blood cell.

Question 18

Which of the following is a steroid that serves as a precursor for many other steroids in the body?

Accepted Answer

Cholesterol

Question 19

A cell membrane is found to be unusually permeable to sodium ions ($$\mathrm{Na^+}). $$Which structural change could explain this observation?

Accepted Answer

Increased number of protein pores specific for sodium ions.

Question 20

Which of the following is a correct statement about the role of fats in living organisms?

Accepted Answer

Fats serve as energy storage and insulation.

Biomolecules and Plasma Membrane Structure: Lipids, Fats, and Transport Mechanisms

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