Q: Which equation best represents the relationship between the number of double bonds in fatty acid tails ($n$) and membrane fluidity ($F$)?

$F = k \times n$, where $k$ is a positive constant

Question 1

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

Accepted Answer

Phospholipids are amphipathic, with hydrophilic heads facing water and hydrophobic tails shielded from water, minimizing free energy.

Question 2

A patient with hereditary spherocytosis has red blood cells that are spherical rather than biconcave. Which molecular defect is most likely responsible for this change in cell shape?

Accepted Answer

Abnormal proteins attaching the membrane to the cytoskeleton, such as spectrin or ankyrin.

Question 3

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membrane fluidity increases with shorter fatty acid chains and more unsaturated tails.

Question 4

Which equation best represents the relationship between the number of double bonds in fatty acid tails ($n$) and membrane fluidity ($F$)?

Accepted Answer

$F = k 	imes n$, where $k$ is a positive constant

Question 5

Which of the following best describes the asymmetry of the plasma membrane?

Accepted Answer

The cytosolic and non-cytosolic leaflets have different lipid and protein compositions, with carbohydrate groups facing the extracellular space.

Question 6

A mutation causes loss of flippase activity in a cell. What is the most likely consequence?

Accepted Answer

Phospholipid distribution between the two leaflets will become less asymmetrical.

Question 7

Which of the following membrane proteins is most likely to form an aqueous channel across the lipid bilayer?

Accepted Answer

Multipass transmembrane protein with amphipathic alpha helices.

Question 8

During membrane synthesis, which organelle is primarily responsible for the initial assembly of new phospholipids?

Accepted Answer

Smooth endoplasmic reticulum (SER)

Question 9

Which of the following best explains how the orientation of membrane lipids and proteins is preserved during vesicle transport?

Accepted Answer

The cytosolic leaflet of the vesicle always faces the cytosol after fusion, maintaining orientation.

Question 10

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

Accepted Answer

Facilitating cell-cell adhesion and recognition by presenting carbohydrate groups.

Question 11

A cell fusion experiment mixes human and mouse cells, each with distinct membrane proteins. After fusion, proteins are found to move laterally and mix within the membrane. What does this demonstrate?

Accepted Answer

Membrane proteins can move laterally within the lipid bilayer, demonstrating membrane fluidity.

Question 12

Which of the following would most likely decrease the ability of a red blood cell to pass through narrow capillaries?

Accepted Answer

Loss of spectrin, leading to a spherical cell shape.

Question 13

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

Accepted Answer

Cholesterol tends to stiffen the membrane, reducing fluidity.

Question 14

Which of the following is true regarding the movement of phospholipids in the plasma membrane?

Accepted Answer

Phospholipids can rotate, move laterally, and rarely flip-flop between leaflets.

Question 15

Which of the following best explains why the lipid bilayer is described as a 'fluid mosaic'?

Accepted Answer

Lipids and proteins can move laterally within the bilayer, creating a dynamic and heterogeneous structure.

Question 16

Which of the following is a correct description of a single-pass transmembrane protein?

Accepted Answer

It spans the lipid bilayer once with a hydrophobic alpha helix.

Question 17

Which of the following best describes the carbohydrate layer (glycocalyx) on the cell surface?

Accepted Answer

It is formed by carbohydrates attached to proteins and lipids facing the extracellular space.

Question 18

Which process is responsible for the transfer of membrane orientation during vesicle transport from the Golgi to the plasma membrane?

Accepted Answer

Vesicle budding and fusion, which preserves the orientation of the lipid bilayer.

Question 19

Which of the following is a consequence of removing carbohydrate groups from the cell surface?

Accepted Answer

Impaired cell-cell recognition and adhesion.

3) Cell Membrane Structure and Function: Composition, Dynamics, and Clinical Relevance

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