Q: A cell is placed in a solution containing 100 mM NaCl, 15 mM MgCl$$_2$$, and 100 mM glucose. What is the total osmolarity of the solution?

$$100 \times 2 + 15 \times 3 + 100 = 245$$ mOsm

Q: A solution contains 50 mM KCl, 50 mM fructose, and 50 mM galactose. What is the total osmolarity of the solution?

$$50 \times 2 + 50 + 50 = 200$$ mOsm

Question 1

Which of the following best describes the main function of the plasma membrane in terms of transport?

Accepted Answer

It is a selective, differentially permeable barrier that regulates the passage of certain substances.

Question 2

Which of the following is an example of passive transport across the cell membrane?

Accepted Answer

Facilitated diffusion of glucose through a carrier protein

Question 3

A cell is placed in a solution containing 100 mM NaCl, 15 mM MgCl$$_2$$, and 100 mM glucose. What is the total osmolarity of the solution?

Accepted Answer

$$100 	imes 2 + 15 	imes 3 + 100 = 245$$ mOsm

Question 4

Which of the following factors would decrease the rate of diffusion across a membrane, according to Fick's Law?

Accepted Answer

Increasing the viscosity of the medium

Question 5

A patient has pulmonary edema, which increases the thickness of the alveolar membrane. According to Fick's Law, how will this affect oxygen diffusion into the blood?

Accepted Answer

Oxygen diffusion will decrease because the membrane thickness ($$x) is $$greater.

Question 6

Which of the following best explains why cells are small in size?

Accepted Answer

Diffusion is very fast over short distances but extremely slow over long distances due to the $$t = \frac{d^2$}{6D}$$ relationship.

Question 7

A red blood cell is placed in a hypotonic solution. What will happen to the cell and why?

Accepted Answer

The cell will swell and may burst because water moves into the cell.

Question 8

Which of the following statements about entropy and diffusion is correct?

Accepted Answer

Diffusion increases entropy as molecules move from areas of high concentration to low concentration.

Question 9

If the surface area for diffusion in the lungs is halved (e.g., one lung collapses), what happens to the rate of oxygen diffusion?

Accepted Answer

It is reduced by half

Question 10

Which of the following best describes the direction of water movement during osmosis?

Accepted Answer

From a hypotonic solution to a hypertonic solution

Question 11

A solution contains 50 mM KCl, 50 mM fructose, and 50 mM galactose. What is the total osmolarity of the solution?

Accepted Answer

$$50 	imes 2 + 50 + 50 = 200$$ mOsm

Question 12

Which of the following is true regarding the difference between osmolarity and tonicity?

Accepted Answer

Osmolarity refers to the total concentration of all solute particles, while tonicity refers to the effect of non-permeating solutes on cell volume.

Question 13

A cell with an internal osmolarity of 290 mOsm is placed in a 400 mOsm NaCl solution. What will happen to the cell?

Accepted Answer

It will shrink as water leaves the cell.

Question 14

Which of the following best explains why drinking seawater is dangerous for human cells?

Accepted Answer

Seawater is hypertonic to human cells, causing water to leave the cells and leading to dehydration.

Question 15

Which of the following equations correctly represents Fick's Law for the flux of diffusion across a membrane?

Accepted Answer

$$	ext{Flux} = \frac{A 	imes D 	imes (C_1$ - C_2$)}{x}$$

Question 16

If the diffusion constant ($$D) $$for a molecule increases, what happens to the time required for it to diffuse a given distance, according to $$t = \frac{d^2$}{6D}$$?

Accepted Answer

The time decreases

Question 17

Which of the following is a characteristic of active transport but NOT passive transport?

Accepted Answer

Requires direct input of energy, usually in the form of ATP

Question 18

Which of the following would most likely diffuse freely across the lipid bilayer of a cell membrane?

Accepted Answer

A small, hydrophobic molecule

Question 19

A cell is placed in a solution with a higher concentration of non-permeating solutes than inside the cell. What type of solution is this, and what is the expected effect on the cell?

Accepted Answer

Hypertonic; the cell will shrink

Physiology of Cell Membrane Transport – Study Notes (BIOL 2401, Chapter 3)

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