Question 1

Which of the following best describes the function of the glycocalyx as seen in the electron micrograph of intestinal epithelial cells?

Accepted Answer

It provides a protective layer that helps retain water and shields the cell from mechanical and chemical damage.

Question 2

Which of the following statements about the fluid mosaic model of the plasma membrane is correct?

Accepted Answer

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

Question 3

A mutation causes a transmembrane protein to be synthesized without a stop-transfer sequence. What is the most likely outcome for this protein?

Accepted Answer

It will be fully translocated into the lumen of the endoplasmic reticulum.

Question 4

Which equation correctly represents the Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for an ion across a membrane?

Accepted Answer

$$E_{ion} = \frac{RT}{zF} \ln \left( \frac{[ion]_{out}}{[ion]_{in}} \right)$$

Question 5

Which of the following best explains why glucose is transported into intestinal epithelial cells via a sodium-glucose symporter?

Accepted Answer

The symporter uses the energy stored in the sodium gradient to move glucose against its concentration gradient.

Question 6

Which of the following is a key difference between channel proteins and carrier proteins in the plasma membrane?

Accepted Answer

Channel proteins form hydrophilic pores that allow specific molecules or ions to pass through by diffusion.

Question 7

A patient is diagnosed with cystic fibrosis, a disease caused by a defect in the CFTR protein. Which process is most directly affected?

Accepted Answer

Facilitated diffusion of chloride ions across epithelial cell membranes.

Question 8

Which of the following best describes the process of receptor-mediated endocytosis?

Accepted Answer

Cells internalize specific molecules bound to receptors via clathrin-coated vesicles.

Question 9

Which of the following statements about lipid rafts is correct?

Accepted Answer

Lipid rafts are dynamic microdomains that compartmentalize cellular processes and are enriched in cholesterol and sphingolipids.

Question 10

Which of the following best explains why the sodium-potassium pump is considered an electrogenic pump?

Accepted Answer

It generates a net movement of positive charge out of the cell, contributing to the membrane potential.

Question 11

Which of the following is the correct sequence of events during clathrin-mediated endocytosis?

Accepted Answer

Receptor binding, clathrin recruitment, vesicle budding, vesicle uncoating

Question 12

A cell is placed in a solution with a high concentration of potassium ions outside and a low concentration inside. If a potassium channel opens, what will happen?

Accepted Answer

Potassium ions will move into the cell by diffusion.

Question 13

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

Accepted Answer

They prevent the diffusion of membrane proteins and lipids between the apical and basolateral surfaces.

Question 14

Which of the following equations correctly describes the electrochemical gradient for an ion?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[ion]_{in} }{ [ion]_{out} } \right) + zF\Delta V$$

Question 15

Which of the following is a consequence of the asymmetric distribution of phospholipids in the plasma membrane?

Accepted Answer

Specific signaling molecules are generated only on one side of the membrane.

Question 16

Which of the following best explains why facilitated diffusion is considered passive transport?

Accepted Answer

It allows molecules to move down their concentration gradient without energy input.

Question 17

A researcher observes that a certain membrane protein is only found on the apical surface of epithelial cells. Which cellular structure is most likely responsible for this localization?

Accepted Answer

Tight junctions

Question 18

Which of the following best describes the function of ABC transporters in the plasma membrane?

Accepted Answer

They use the energy of ATP hydrolysis to actively transport a variety of molecules across membranes.

Question 19

Which of the following is a real-world example of receptor-mediated endocytosis?

Accepted Answer

Uptake of LDL cholesterol by liver cells

Question 20

Which of the following best explains why the plasma membrane is described as 'selectively permeable'?

Accepted Answer

It allows some molecules to cross more easily than others due to the presence of specific transport proteins and the lipid bilayer.

Plasma Membrane Structure and Function: Cell Biology Study Notes

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