Which plasma membrane component can be either found on its surface or embedded in the membrane structure?
Which characteristic of a phospholipid contributes to the fluidity of the membrane?
- its head
- a saturated fatty acid tail
- double bonds in the fatty acid tail
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
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 one of higher concentration
The principal force driving movement in diffusion is the __________.
- particle size
- concentration gradient
- membrane surface area
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.
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
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
What is the combination of an electrical gradient and a concentration gradient called?
- potential gradient
- electrical potential
- concentration potential
- electrochemical gradient
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.
Which transport mechanism can bring whole cells into a cell?
- facilitated transport
- primary active transport
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.