Review Questions
4. Which plasma membrane component can be either found on its surface or embedded in the membrane structure?
- protein
- cholesterol
- carbohydrate
- phospholipid
5. Which characteristic of a phospholipid contributes to the fluidity of the membrane?
- its head
- cholesterol
- a saturated fatty acid tail
- double bonds in the fatty acid tail
6. What is the primary function of carbohydrates attached to the exterior of cell membranes?
- identification of the cell
- flexibility of the membrane
- strengthening the membrane
- channels through membrane
7. A scientist compares the plasma membrane composition of an animal from the Mediterranean coast with one from the Mojave Desert. Which hypothesis is most likely to be correct?
- The cells from the Mediterranean coast animal will have more fluid plasma membranes.
- The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.
- The cells’ plasma membranes will be indistinguishable.
- The cells from the Mediterranean coast animal will have a higher glycoprotein content, while the cells from the Mojave Desert animal will have a higher lipoprotein content.
8. Water moves via osmosis _________.
- throughout the cytoplasm
- from an area with a high concentration of other solutes to a lower one
- from an area with a high concentration of water to one of lower concentration
- from an area with a low concentration of water to higher concentration
9. The principal force driving movement in diffusion is the __________.
- temperature
- particle size
- concentration gradient
- membrane surface area
10. What problem is faced by organisms that live in fresh water?
- Their bodies tend to take in too much water.
- They have no way of controlling their tonicity.
- Only salt water poses problems for animals that live in it.
- Their bodies tend to lose too much water to their environment.
11. In which situation would passive transport not use a transport protein for entry into a cell?
- water flowing into a hypertonic environment
- glucose being absorbed from the blood
- an ion flowing into a nerve cell to create an electrical potential
- oxygen moving into a cell after oxygen deprivation
12. Active transport must function continuously because __________.
- plasma membranes wear out
- not all membranes are amphiphilic
- facilitated transport opposes active transport
- diffusion is constantly moving solutes in opposite directions
13. How does the sodium-potassium pump make the interior of the cell negatively charged?
- by expelling anions
- by pulling in anions
- by expelling more cations than are taken in
- by taking in and expelling an equal number of cations
14. What is the combination of an electrical gradient and a concentration gradient called?
- potential gradient
- electrical potential
- concentration potential
- electrochemical gradient
15. What happens to the membrane of a vesicle after exocytosis?
- It leaves the cell.
- It is disassembled by the cell.
- It fuses with and becomes part of the plasma membrane.
- It is used again in another exocytosis event.
16. Which transport mechanism can bring whole cells into a cell?
- pinocytosis
- phagocytosis
- facilitated transport
- primary active transport
17. In what important way does receptor-mediated endocytosis differ from phagocytosis?
- It transports only small amounts of fluid.
- It does not involve the pinching off of membrane.
- It brings in only a specifically targeted substance.
- It brings substances into the cell, while phagocytosis removes substances.
18. Many viruses enter host cells through receptor-mediated endocytosis. What is an advantage of this entry strategy?
- The virus directly enters the cytoplasm of the cell.
- The virus is protected from recognition by white blood cells.
- The virus only enters its target host cell type.
- The virus can directly inject its genome into the cell’s nucleus.
19. Which of the following organelles relies on exocytosis to complete its function?
- Golgi apparatus
- vacuole
- mitochondria
- endoplasmic reticulum
20. Imagine a cell can perform exocytosis, but only minimal endocytosis. What would happen to the cell?
- The cell would secrete all its intracellular proteins.
- The plasma membrane would increase in size over time.
- The cell would stop expressing integral receptor proteins in its plasma membrane.
- The cell would lyse.