Question 1

Which of the following best describes the amphipathic nature of phospholipids in the plasma membrane?

Accepted Answer

They have both a hydrophilic head and a hydrophobic tail.

Question 2

A mutation causes a cell to produce phospholipids with much longer hydrocarbon tails. What is the most likely effect on the plasma membrane?

Accepted Answer

The membrane will become less fluid due to increased van der Waals interactions.

Question 3

Which enzyme is responsible for the random distribution of newly synthesized phospholipids between the two leaflets of the ER membrane?

Accepted Answer

Scramblase

Question 4

Why do phospholipid bilayers spontaneously form closed compartments in aqueous environments?

Accepted Answer

To avoid exposing hydrophobic tails to water, minimizing free energy.

Question 5

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

Accepted Answer

Cholesterol can both increase and decrease membrane fluidity depending on the context.

Question 6

A researcher observes that a certain membrane protein is only found on the cytosolic side of the plasma membrane and is covalently attached to a lipid. What type of membrane protein is this?

Accepted Answer

Lipid-linked protein

Question 7

Which of the following best explains why unsaturated fatty acid chains increase membrane fluidity?

Accepted Answer

Double bonds introduce kinks, preventing tight packing of lipid tails.

Question 8

Which of the following is a function of the carbohydrate layer (glycocalyx) on the cell surface?

Accepted Answer

Protects the cell from mechanical damage and aids in cell-cell recognition.

Question 9

A patient has a genetic defect in flippase enzymes. Which of the following is a likely consequence?

Accepted Answer

Asymmetric distribution of phospholipids in the plasma membrane will be disrupted.

Question 10

Which of the following best describes the movement of lipids within the plasma membrane?

Accepted Answer

Lipids can rapidly diffuse laterally within the same leaflet but rarely flip-flop between leaflets.

Question 11

Which of the following is a real-life example of the importance of cell-surface carbohydrates?

Accepted Answer

Neutrophils use glycoproteins to adhere to blood vessel walls during infection.

Question 12

Which of the following equations best represents the relationship between the rate of lateral diffusion ($$D) $$and the viscosity ($$\eta) of $$the membrane?

Accepted Answer

$$D \propto \frac{1}{\eta}$$

Question 13

A scientist is studying a membrane protein that forms an aqueous pore across the membrane. Which structural feature is most likely present in this protein?

Accepted Answer

Multiple amphipathic alpha helices forming a channel

Question 14

Which of the following best explains why detergents are effective at solubilizing membrane proteins?

Accepted Answer

Detergents have hydrophobic and hydrophilic regions that interact with both membrane proteins and water.

Question 15

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

Accepted Answer

Synthesizing DNA for cell division

Question 16

Which of the following best describes the role of spectrin in red blood cells?

Accepted Answer

It forms a meshwork that supports the plasma membrane and maintains cell shape.

Question 17

Which of the following statements about membrane protein mobility is correct?

Accepted Answer

Some membrane proteins are restricted to specific domains by tethering or diffusion barriers.

Question 18

Which of the following best explains why the inside and outside faces of cellular membranes remain distinct during vesicular transport?

Accepted Answer

The orientation of membrane proteins and lipids is preserved during vesicle fusion.

Question 19

Which of the following is a consequence of the amphipathic nature of membrane lipids?

Accepted Answer

They spontaneously form bilayers in aqueous environments.

Structure and Function of Cell Membranes: Genetics Study Guide

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