Question 1

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

Accepted Answer

They contain both hydrophilic and hydrophobic regions, allowing them to spontaneously assemble into bilayers in aqueous environments.

Question 2

A mutation causes a cell to produce only saturated fatty acids in its membrane phospholipids. What is the most likely effect on the membrane's properties?

Accepted Answer

The membrane will become more viscous and less fluid due to tight packing of the fatty acid tails.

Question 3

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

Accepted Answer

Cholesterol acts as a temperature buffer, decreasing membrane fluidity at high temperatures and preventing tight packing at low temperatures.

Question 4

Which movement of phospholipids within the bilayer is energetically least favorable and occurs rarely without enzymatic assistance?

Accepted Answer

Flip-flop (transverse diffusion) from one leaflet to the other.

Question 5

A patient receives a blood transfusion with mismatched ABO blood type. What is the molecular basis for the immune response that occurs?

Accepted Answer

The carbohydrate chains (antigens) on the donor's red blood cells differ from those of the recipient, triggering an immune response.

Question 6

Which of the following best explains why the plasma membrane is described as a 'fluid mosaic'?

Accepted Answer

Membrane proteins and lipids move laterally within the bilayer, and the membrane is composed of a diverse set of molecules.

Question 7

Which of the following is a critical function of the glycocalyx on the cell surface?

Accepted Answer

Protection against mechanical damage and facilitating cell-cell adhesion.

Question 8

Which phospholipid is found predominantly on the cytosolic (inner) leaflet of the plasma membrane?

Accepted Answer

Phosphatidylserine

Question 9

A researcher observes that a certain membrane protein is only temporarily attached to the cytosolic surface of the plasma membrane via non-covalent interactions. This protein is best classified as:

Accepted Answer

A peripheral membrane protein

Question 10

Which of the following best describes the effect of unsaturated fatty acid tails on membrane fluidity?

Accepted Answer

They introduce kinks that prevent tight packing, increasing membrane fluidity.

Question 11

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

Accepted Answer

Synthesis of phospholipids

Question 12

Which of the following statements about the asymmetry of the plasma membrane is correct?

Accepted Answer

Glycolipids are found exclusively on the extracellular (noncytosolic) face of the membrane.

Question 13

A red blood cell membrane contains the O antigen. Which additional sugar residue must be added to convert it to the A antigen?

Accepted Answer

N-acetylgalactosamine

Question 14

Which of the following best explains why the plasma membrane is only visible as a double line under electron microscopy and not under light microscopy?

Accepted Answer

The membrane is only 7.5 nm thick, below the resolution limit of light microscopes.

Question 15

Which of the following scenarios would most likely increase the permeability of a cell membrane to small water-soluble molecules?

Accepted Answer

Decreasing cholesterol content in the membrane

Question 16

A scientist is studying a membrane protein that spans the lipid bilayer with multiple alpha-helical segments. This protein is most accurately described as:

Accepted Answer

An integral (transmembrane) protein

Question 17

Which of the following best describes the role of the cytoskeleton in relation to the plasma membrane?

Accepted Answer

It provides structural support and restricts the mobility of membrane proteins.

Question 18

Which of the following is a direct consequence of the amphipathic nature of phospholipids in water?

Accepted Answer

They spontaneously form bilayers with hydrophobic tails facing inward and hydrophilic heads facing outward.

Question 19

Which of the following best explains why lateral diffusion of phospholipids is much faster than flip-flop movement?

Accepted Answer

Lateral diffusion does not require the hydrophilic head to cross the hydrophobic core of the bilayer.

Cellular Membranes: Structure, Function, and Identity (Chapter 15 Study Guide)

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