Q: Which equation best represents the percentage composition of phospholipids and glycolipids in the plasma membrane?

$$75\% \text{ phospholipids} + 5\% \text{ glycolipids}$$

Question 1

Which of the following best describes the primary structural role of a lipid bilayer in the plasma membrane?

Accepted Answer

It acts as a selectively permeable barrier, allowing certain molecules to pass while restricting others.

Question 2

A phospholipid molecule in the plasma membrane is described as amphipathic. What does this mean?

Accepted Answer

It contains both hydrophilic and hydrophobic regions.

Question 3

If a membrane protein is described as 'integral,' what is its most likely location?

Accepted Answer

It is embedded within the lipid bilayer, often spanning the membrane.

Question 4

Which of the following is TRUE regarding cholesterol in the plasma membrane?

Accepted Answer

Cholesterol is embedded in the hydrophobic part of the lipid bilayer.

Question 5

A protein that is bound to the cytoskeleton and extracellular matrix (ECM) is most likely involved in which function?

Accepted Answer

Providing structural support and anchoring the cell.

Question 6

Which equation best represents the percentage composition of phospholipids and glycolipids in the plasma membrane?

Accepted Answer

$$75\% 	ext{ phospholipids} + 5\% 	ext{ glycolipids}$$

Question 7

Which of the following membrane proteins is most likely to function as a receptor for signal transduction?

Accepted Answer

An integral protein with a binding site for specific molecules.

Question 8

A mutation causes a membrane protein to lose its hydrophobic amino acids. What is the most likely consequence?

Accepted Answer

The protein will have difficulty embedding in the membrane and may become peripheral.

Question 9

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

Accepted Answer

They are unique for every individual and are involved in cell-cell recognition.

Question 10

A cell is unable to communicate with its environment due to a defect in its membrane proteins. Which function is most likely impaired?

Accepted Answer

Cell-to-cell communication, signal reception, and response.

Question 11

Which of the following best explains why some amino acids in transmembrane proteins are hydrophobic?

Accepted Answer

Hydrophobic amino acids interact favorably with the lipid bilayer, allowing the protein to embed within the membrane.

Question 12

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

Accepted Answer

Synthesis of DNA.

Question 13

A researcher is studying a membrane protein that is only loosely attached to the surface of the plasma membrane. What type of protein is this?

Accepted Answer

Peripheral protein.

Question 14

Which of the following best describes the role of glycolipids in the plasma membrane?

Accepted Answer

They are involved in cell recognition and are found on the surface of the membrane.

Question 15

A cell is exposed to a toxin that disrupts the attachment of membrane proteins to the cytoskeleton. What is the most likely effect?

Accepted Answer

The cell will lose its structural integrity and shape.

Question 16

Which of the following is a correct statement about the distribution of cholesterol in the plasma membrane?

Accepted Answer

Cholesterol is found in the hydrophobic part of the lipid bilayer.

Question 17

Which of the following best describes the function of enzymes attached to the plasma membrane?

Accepted Answer

They catalyze specific reactions at the membrane surface.

Question 18

A cell is found to have defective glycoproteins on its surface. Which process is most likely to be affected?

Accepted Answer

Cell-cell recognition.

Question 19

Which of the following is a multi-step process involving membrane proteins that allows a cell to respond to external signals?

Accepted Answer

Signal reception by a receptor protein, followed by activation of intracellular pathways.

Question 20

If a cell's plasma membrane is composed of $$75\%$$ phospholipids, $$5\%$$ glycolipids, and $$20\%$$ cholesterol, what is the total percentage of non-protein lipids in the membrane?

Accepted Answer

$$75\% + 5\% + 20\% = 100\%$$

Structure and Function of the Plasma Membrane

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