Question 1

Which of the following molecules would most readily diffuse across a plasma membrane by simple diffusion, according to the size, charge, and polarity rules?

Accepted Answer

O$$_2$$

Question 2

A patient with cystic fibrosis has a mutation in the CFTR protein. Which process is most directly affected by this mutation?

Accepted Answer

Ion channel diffusion of Cl$$^-$$

Question 3

Which of the following best explains why cholesterol increases membrane fluidity at low temperatures but decreases permeability to water?

Accepted Answer

Cholesterol disrupts close packing of phospholipid tails, increasing fluidity but filling gaps, making the membrane more hydrophobic

Question 4

Which of the following is an example of active transport?

Accepted Answer

Sodium-potassium pump moving Na$$^+$$ out and K$$^+ in$$

Question 5

A red blood cell is placed in a solution containing a high concentration of urea. Urea is a small, polar molecule. Which transport mechanism will primarily allow urea to enter the cell?

Accepted Answer

Facilitated diffusion via a carrier protein

Question 6

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It requires ATP to function

Question 7

Which of the following best describes the process shown in the image of endocytosis?

Accepted Answer

The cell engulfs extracellular material by forming a vesicle from the plasma membrane

Question 8

Which of the following would increase the permeability of a cell membrane to small polar molecules?

Accepted Answer

Increasing the number of unsaturated fatty acids in the membrane

Question 9

A scientist adds gramicidin to a bacterial culture. What is the most likely effect on the bacteria?

Accepted Answer

Increased ion flow across the membrane, disrupting ion gradients

Question 10

Which of the following best explains why ions such as Na$$^+$$ and Cl$$^-$$ cannot easily cross the plasma membrane by simple diffusion?

Accepted Answer

They are charged and the membrane interior is hydrophobic

Question 11

Which process is illustrated by the movement of glucose into erythrocytes via GLUT-1?

Accepted Answer

Facilitated diffusion

Question 12

A cell is placed in a hypotonic solution. Which direction will water move, and by what process?

Accepted Answer

Water will move into the cell by osmosis

Question 13

Which of the following is true about cotransport (symport and antiport) systems?

Accepted Answer

They can be either passive or active depending on the molecules and pumps involved

Question 14

Which of the following best describes the relationship between hydrophobicity and rate of diffusion across a membrane, as shown in the provided graph?

Accepted Answer

As hydrophobicity increases, the rate of diffusion increases

Question 15

Which of the following scenarios best illustrates indirect active transport?

Accepted Answer

A glucose transporter uses the Na$$^+$$ gradient established by the sodium-potassium pump to move glucose into the cell

Question 16

Which of the following is NOT a characteristic of facilitated diffusion?

Accepted Answer

It requires cellular energy (ATP)

Question 17

Which process is responsible for the uptake of large particles, such as bacteria, by immune cells?

Accepted Answer

Phagocytosis

Question 18

Which of the following would most likely decrease the rate of simple diffusion of a small nonpolar molecule across a membrane?

Accepted Answer

Decreasing the temperature

Question 19

Which of the following best describes the function of an ionophore such as valinomycin?

Accepted Answer

It binds ions and facilitates their diffusion across the membrane

Question 20

Which of the following is a direct result of the sodium-potassium pump activity in animal cells?

Accepted Answer

The inside of the cell becomes more negative relative to the outside

Membrane Transport Mechanisms in Cell Biology

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