Chapter 5 - Membranes and Transport

Which of the following statements is correct about diffusion?

It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

Which line in the graph represents the bag with the highest initial concentration of sucrose?

A

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percentage change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?

B

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percentage change in mass of each bag was graphed. Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

CO2

Hypotonic

Having a lower concentration of solute than another solution, net gain of water

Which of the following is TRUE of osmosis?

In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?

The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.

A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?

The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.

Use the diagram of the U-tube in Figure 7.2 to answer the questions that follow.The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half filled with a solution of 2 M sucrose and 1 M glucose. Side B is half filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. After the system reaches equilibrium, what changes are observed?

The water level is higher in side A than in side B.

Why are lipids and proteins free to move laterally in membranes?

There are only weak hydrophobic interactions in the interior of the membrane.

Which aspect of phospholipids is most important to the formation of bilayers?

They are amphiatic

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

They can move laterally along the plane of the membrane.

If you examine side A after 3 days, you should find

a decrease in the concentration of NaCl and a decrease in the water level.

Which of the following crosses lipid bilayers the fastest?

a small, nonpolar molecule like oxygen (O2)

Based on the accompanying figure, which of these experimental treatments would increase the rate of sucrose transport into the cell?

decreasing extracellular pH

Ions diffuse across membranes down their

electrochemical gradients

The presence of cholesterol in the plasma membranes of some animals

enables the membrane to stay fluid more easily when cell temperature drops.

A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms describes the tonicity of the external solution relative to the cytoplasm of the cell?

isotonic

Initially, in terms of tonicity, the solution in side A with respect to that in side B is

isotonic

Which of the following affects the osmolarity of a solution? I) concentration of cations II) concentration of anions III)concentration of water

only I and II

Which of the following processes includes all others?

passive transport

White blood cells engulf bacteria through what process?

phagocytosis

Refer to the figure. At the beginning of the experiment,

side A is hypotonic to side B

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule enters the cell?

similarity of the drug molecule to other molecules transported by the target cells

Hypertonic

when comparing two solutions, the solution with the greater concentration of solutes, net loss of water from cell