Q: Which equation best describes the free energy change ($$\Delta G) $$for the movement of an uncharged solute across a membrane?

$$\Delta G = RT \ln \left( \frac{[C]_\text{outside}}{[C]_\text{inside}} \right)$$

Question 1

Which experimental technique provided direct evidence for the lateral mobility of membrane proteins in the plasma membrane?

Accepted Answer

Cell fusion experiments using fluorescently labeled antibodies

Question 2

A researcher performs a FRAP (Fluorescence Recovery After Photobleaching) experiment on a membrane protein at 10°C and observes no diffusion of the labeled protein. What is the most likely explanation for this observation?

Accepted Answer

The protein is anchored to a cytoskeletal or extracellular structure, restricting its mobility.

Question 3

Which of the following best describes the function of the GLUT1 transporter in erythrocytes?

Accepted Answer

It is a uniporter that facilitates the passive transport of glucose down its concentration gradient.

Question 4

Which of the following molecules is LEAST likely to cross a pure lipid bilayer by simple diffusion?

Accepted Answer

Glucose (MW = 180, polar)

Question 5

A cell is placed in a hypertonic solution. What is the most likely outcome for an animal cell?

Accepted Answer

The cell will shrink and shrivel due to water loss.

Question 6

Which of the following statements about facilitated diffusion is TRUE?

Accepted Answer

It exhibits saturation kinetics similar to enzyme-catalyzed reactions.

Question 7

The chloride-bicarbonate exchanger in erythrocytes is an example of which type of transporter?

Accepted Answer

Antiporter

Question 8

Which of the following best explains why the rate of facilitated diffusion plateaus at high substrate concentrations?

Accepted Answer

All available transport proteins become saturated with substrate.

Question 9

Which of the following is a key feature of membrane domains (lipid rafts)?

Accepted Answer

They are regions of the membrane with distinct protein and lipid composition, often enriched in sphingolipids and cholesterol.

Question 10

A patient has a genetic defect in ankyrin, a protein associated with the erythrocyte membrane. Which of the following is a likely consequence?

Accepted Answer

Erythrocytes will have abnormal shapes and reduced mechanical stability.

Question 11

Which equation best describes the free energy change ($$\Delta G) $$for the movement of an uncharged solute across a membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[C]_	ext{outside}}{[C]_	ext{inside}} ight)$$

Question 12

Which of the following best explains why most animal cells maintain a low intracellular glucose concentration after glucose uptake?

Accepted Answer

Glucose is rapidly phosphorylated to glucose-6-phosphate, preventing its exit via GLUT1.

Question 13

Which of the following is a property shared by both carrier proteins and enzymes?

Accepted Answer

They exhibit specificity for their substrates and can be regulated by external factors.

Question 14

A cell is placed in a hypotonic solution. Which of the following best describes the response of a plant cell compared to an animal cell?

Accepted Answer

The plant cell becomes turgid due to its cell wall, while the animal cell may burst.

Question 15

Which of the following statements about the alternating conformation model of carrier proteins is CORRECT?

Accepted Answer

The carrier protein alternates between two conformations, exposing the solute-binding site to opposite sides of the membrane.

Question 16

Which of the following best describes the movement of ions across a membrane in terms of electrochemical potential?

Accepted Answer

It is determined by both the concentration gradient and the membrane potential.

Question 17

Which of the following is a real-world example of an antiport mechanism in human physiology?

Accepted Answer

The chloride-bicarbonate exchanger in erythrocytes during CO$$_2$$ transport.

Question 18

Which of the following changes would you expect in the membrane lipids of an organism that thrives at 10°C compared to one that lives at 37°C?

Accepted Answer

More unsaturated fatty acids to maintain membrane fluidity at lower temperatures.

Question 19

Which of the following best explains why the COVID mRNA vaccines require lipid nanoparticles for delivery into cells?

Accepted Answer

mRNA is highly charged and cannot cross the hydrophobic lipid bilayer without assistance.

Membrane Protein Mobility and Transport Mechanisms in Cell Biology

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