Question 1

Which of the following best describes why phospholipids spontaneously form bilayers in aqueous environments?

Accepted Answer

Because their amphipathic nature causes hydrophilic heads to interact with water and hydrophobic tails to avoid water, resulting in a bilayer.

Question 2

A patient is found to have a genetic mutation that results in the production of phospholipids with much longer fatty acid tails than normal. What effect would this have on the fluidity of their cell membranes at physiological temperature?

Accepted Answer

Membrane fluidity would decrease because longer tails increase van der Waals interactions.

Question 3

Which of the following statements about cholesterol in the plasma membrane is TRUE?

Accepted Answer

Cholesterol is amphipathic due to its hydroxyl group, but is weakly amphipathic because most of its structure is hydrophobic.

Question 4

Which of the following best explains the difference between a phospholipid and a triacylglycerol molecule?

Accepted Answer

Phospholipids have a phosphate group and two fatty acid tails, making them amphipathic, while triacylglycerols have three fatty acid tails and are entirely hydrophobic.

Question 5

A researcher adds a small amount of phospholipid to water, not enough to form a liposome. What structure is most likely to form?

Accepted Answer

A micelle

Question 6

Which of the following best describes the 'fluid mosaic model' of biological membranes?

Accepted Answer

Membranes consist of a fluid lipid bilayer with proteins and other molecules embedded and able to move laterally.

Question 7

Which of the following changes would most likely increase the transition temperature ($T_m$) of a membrane?

Accepted Answer

Increasing the length of fatty acid tails

Question 8

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

Accepted Answer

Serving as recognition sites for cell-cell interactions

Question 9

A scientist is studying a membrane protein that can only be extracted from the membrane using detergents. This protein is most likely:

Accepted Answer

An integral membrane protein

Question 10

Which of the following best describes the orientation of amino acids in a beta barrel transmembrane protein?

Accepted Answer

Hydrophobic amino acids face the membrane, hydrophilic face the interior of the barrel.

Question 11

Which of the following statements about lipid rafts is TRUE?

Accepted Answer

Lipid rafts are more ordered and tightly packed than the surrounding membrane.

Question 12

Which enzyme is responsible for the specific redistribution of newly synthesized phospholipids between the leaflets of the ER membrane?

Accepted Answer

Flippase

Question 13

A cell is exposed to low temperatures, causing its membrane to become less fluid. Which adaptation would most likely help restore membrane fluidity?

Accepted Answer

Increasing the proportion of unsaturated fatty acids

Question 14

Which of the following best describes the function of tight junctions in epithelial cells?

Accepted Answer

They restrict the lateral mobility of membrane proteins, maintaining distinct membrane domains.

Question 15

Which of the following statements about the glycocalyx is CORRECT?

Accepted Answer

It consists of carbohydrate chains attached to proteins and lipids on the extracellular surface.

Question 16

Which of the following best explains how cholesterol acts as a 'fluidity buffer' in animal cell membranes?

Accepted Answer

It prevents sharp transitions in membrane fluidity by restricting movement at high temperatures and preventing tight packing at low temperatures.

Question 17

A researcher uses fluorescence recovery after photobleaching (FRAP) to study a membrane protein. Which result would indicate that the protein is highly mobile within the membrane?

Accepted Answer

Rapid recovery of fluorescence in the bleached area.

Question 18

Which of the following best describes a GPI-anchored protein?

Accepted Answer

It is covalently attached to a glycosylphosphatidylinositol anchor on the outer leaflet of the plasma membrane.

Question 19

Which of the following is a common function of lectins in vascular endothelial cells?

Accepted Answer

They bind specific carbohydrate groups on leukocytes to mediate extravasation.

Question 20

Which of the following types of movement is LEAST likely for a phospholipid in a biological membrane?

Accepted Answer

Transverse (flip-flop) movement between leaflets

Cell Membrane Structure and Function – Study Guidance

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