Review Questions

Which plasma membrane component can be either found on its surface or embedded in the membrane structure?

1. protein
2. cholesterol
3. carbohydrate
4. phospholipid

Which characteristic of a phospholipid contributes to the fluidity of the membrane?

1. its head
2. cholesterol
3. a saturated fatty acid tail
4. double bonds in the fatty acid tail

What is the primary function of carbohydrates attached to the exterior of cell membranes?

1. identification of the cell
2. flexibility of the membrane
3. strengthening the membrane
4. channels through membrane

Water moves via osmosis _________.

1. throughout the cytoplasm
2. from an area with a high concentration of other solutes to a lower one
3. from an area with a high concentration of water to one of lower concentration
4. from an area with a low concentration of water to one of higher concentration

The principal force driving movement in diffusion is the __________.

1. temperature
2. particle size
3. concentration gradient
4. membrane surface area

What problem is faced by organisms that live in fresh water?

1. Their bodies tend to take in too much water.
2. They have no way of controlling their tonicity.
3. Only salt water poses problems for animals that live in it.
4. Their bodies tend to lose too much water to their environment.

Active transport must function continuously because __________.

1. plasma membranes wear out
2. not all membranes are amphiphilic
3. facilitated transport opposes active transport
4. diffusion is constantly moving solutes in opposite directions

How does the sodium-potassium pump make the interior of the cell negatively charged?

1. by expelling anions
2. by pulling in anions
3. by expelling more cations than are taken in
4. by taking in and expelling an equal number of cations

What is the combination of an electrical gradient and a concentration gradient called?

1. potential gradient
2. electrical potential
3. concentration potential
4. electrochemical gradient

What happens to the membrane of a vesicle after exocytosis?

1. It leaves the cell.
2. It is disassembled by the cell.
3. It fuses with and becomes part of the plasma membrane.
4. It is used again in another exocytosis event.

Which transport mechanism can bring whole cells into a cell?

1. pinocytosis
2. phagocytosis
3. facilitated transport
4. primary active transport

In what important way does receptor-mediated endocytosis differ from phagocytosis?

1. It transports only small amounts of fluid.
2. It does not involve the pinching off of membrane.
3. It brings in only a specifically targeted substance.
4. It brings substances into the cell, while phagocytosis removes substances.