Chapter 7

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

Which of the following statements correctly describes 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 describes a characteristic feature of a carrier protein in a plasma membrane?

It exhibits specificity for a particular type of molecule.

Which of the following statements about diffusion is true?

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

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

O2

The force driving simple diffusion is ________, while the energy source for active transport is ________.

a concentration gradient; ATP hydrolysis

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

In which of the following environments would there be the greatest need for osmoregulation?

a salmon moving from a river into an ocean

For a protein to be an integral membrane protein, it would have to be ________.

amphipathic, with at least one hydrophobic region

Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes?

aquaporins

According to the fluid mosaic model of cell membranes, phospholipids ________.

can move laterally along the plane of the membrane

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane—more acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of ________.

cotransport

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

embedded in a lipid bilayer.

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.

increasing the proportion of unsaturated phospholipids in the membrane

According to the fluid mosaic model, a membrane ________.

is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in ________.

lysosomes

The voltage across a membrane is called the ________.

membrane potential

A sodium-potassium pump ________.

moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis

Which of the following processes includes all of the others?

passive transport

Which of the following processes includes all the others?

passive transport

An organism with a cell wall would most likely be unable to take in materials through ________.

phagocytosis

White blood cells engulf bacteria using ________

phagocytosis

The difference between pinocytosis and receptor-mediated endocytosis is that ________.

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity

What kinds of molecules pass through a cell membrane most easily?

small and hydrophobic

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?

small ions