Which of these statements describes the plasma membrane
A)The hydrophobic interior of its lipid bilayer blocks the passage of water-soluble substances.
B)The surface carbohydrates within it serve as cell adhesion molecules (CAMs), which cells use to grip one another and surrounding connective tissue fibres.
C)Its outer layer of carbohydrates is the primary barrier to the passage of water-soluble substances.
D)Sheets of epithelial cells are joined by gap junctions.

Question

Quizplus · Accepted Answer

The plasma membrane is made up of a lipid bilayer, with hydrophobic tails facing inward, which makes it impermeable to water-soluble substances.

Answer: B
 Surface carbohydrates in the plasma membrane do serve as cell adhesion molecules (CAMs), which is important for cell-cell and cell-matrix interactions.

Answer: C
 Although carbohydrates are present on the plasma membrane, they are not the primary barrier to the passage of water-soluble substances. The hydrophobic interior of the lipid bilayer is primarily responsible for blocking the passage of such substances.

Answer: D
 This statement does not accurately describe the plasma membrane. Sheaths of epithelial cells are typically held together by tight junctions, not gap junctions, which allow for small molecules to flow between cells.

Which of These Statements Describes the Plasma Membrane