Ch 4: Membrane and Transport

The diagram shows the fluid mosaic model of membrane structure.

Which would enable a hormone to recognise its target cell?

• A

• B

• C

• D

The diagram shows a cell surface membrane.

Which statements about the labelled molecules in the membrane are correct?

· 1 is involved in the diffusion of ions

· 2 is involved in facilitated diffusion

· 3 is involved in the recognition of antigens

· 4 is involved in membrane fluidity

• 1, 2 and 3

• 1 and 3 only

• 1 and 4 only

• 2 and 4 only

• 1, 2, 3 and 4

Which of the following can increase the fluidity of the cell surface membrane at low temperatures?

1. double bonds between carbon atoms in the fatty acid chains

2. cholesterol

3. fatty acids having shorter chains

• 1, 2 and 3

• 1 and 3 only

• 2 and 3 only

• 1 only

• 3 only

What describes the fluid-mosaic model of membrane structure?

• Cholesterol makes the membrane more fluid

• Fluids can cross the membrane by diffusion or osmosis.

• Proteins act as receptors for cell signaling.

• Proteins and phospholipids move and change places.

• none of the above

A plant cell is placed in a solution with a less negative (higher) water potential than the cell contents.

From the table above, which change occurs in the cell and what causes the change?

• A

• B

• C

• D

What happens to an animal cell when it is placed in a solution with a more negative water potential?

• It loses solutes to the solution and swells.

• It loses water by osmosis and shrinks.

• It takes in solutes and swells.

• It takes in water by osmosis and bursts.

• Nothing happens

Which pair of factors is inversely proportional to the rate of diffusion?

• concentration gradient and size of diffusing molecule

• distance over which diffusion occurs and surface area over which diffusion occurs

• size of diffusing molecule and distance over which diffusion occurs

• surface area over which diffusion occurs and concentration gradient

• none of the above

Which statement suggests that a membrane protein is involved in active transport?

• It allows movement of molecules across a membrane if concentration differences exist.

• It can only function if mitochondria are supplied with sufficient oxygen.

• It is found in the cell surface membranes and the mitochondrial membranes.

• It has a tertiary structure with a binding site with a specific shape.

• all of the above

What are the features of facilitated diffusion?

• A

• B

• C

• D

Equal sized potato pieces were placed into test-tubes containing equal volumes of different concentrations of sucrose solution and left for 30 minutes. All other variables were controlled.

After 30 minutes, the potato piece in one of the concentrations of sucrose solution had not changed in size.

What can be concluded from this result?

1. There is no net movement of water into or out of the potato.

2. The water potential of the potato is the same as the water potential of the sucrose solution.

3. The concentration of sucrose in the potato is the same as the concentration of the sucrose solution.

• 1, 2 and 3

• 1 and 3 only

• 1 and 2 only

• 2 only

• 3 only