Mastering Biology-Chapter Seven

Which of the following allows water to move much faster across cell membranes? a. the sodium-potassium pump b. peripheral proteins c. ATP d. aquaporins

d

Endocytosis moves materials _____ a cell via _____. a. out of ... membranous vesicles b. into ... membranous vesicles c. out of ... diffusion d. into ... facilitated diffusion e. into ... a transport protein

b

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis? a. on the outer surface of the nucleus b. on the outside of vesicles c. on the inside surface of the cell membrane d. on the inside surface of the vesicle

d

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium? a. Water molecules move between the two solutions, but there is no net movement of water across the membrane. b.Water molecules no longer move between the solutions. c.Water molecules continue to move from the hypotonic solution to the hypertonic solution.

a

Which of the following statements about a typical plasma membrane is correct? a. The two sides of the plasma membrane have different lipid and protein composition. b. Phospholipids are the primary component that determines which solutes can cross the plasma membrane. c. Carbohydrates on the membrane surface are important in determining the overall bilayer structure. d. T he hydrophilic interior of the membrane is composed primarily of the fatty acid tails of the phospholipids e. The plasma membrane is a covalently linked network of phospholipids and proteins that controls the movement of solutes into and out of a cell.

a

Which statement is correct? a. The contents of a red blood cell are hyperosmotic to distilled water. b. A solution of distilled water is hypotonic. c. A solution of seawater is hypertonic.

a

You can recognize the process of pinocytosis when _____. Click to launch animation a. the cell is engulfing extracellular fluid b. the cell is engulfing a large particle c. a receptor protein is involved

a

In what way do the membranes of a eukaryotic cell vary? a. Phospholipids are found only in certain membranes. b. Certain proteins are unique to each membrane. c. Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm. d. Only certain membranes of the cell are selectively permeable.

b

The permeability of a biological membrane to a specific polar solute may depend on which of the following? a. the amount of cholesterol in the membrane b. the types of transport proteins in the membrane c. the phospholipid composition of the membrane d. the presence of unsaturated fatty acids in the membrane e. the types of polysaccharides present in the membrane

b

Which of the following best describes the structure of a biological membrane? a. two layers of phospholipids with proteins embedded between the two layers b. two layers of phospholipids with proteins either crossing the layers or on the surface of the layers c. two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins d. a fluid structure in which phospholipids and proteins move freely between sides of the membrane e. a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot

b

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in _____. a. vacuoles b. secretory vesicles c. lysosomes d. Golgi vesicles

c

The difference between pinocytosis and receptor-mediated endocytosis is that _____. a. pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well. b. pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area. c. pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity. d. pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

c

When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell? a. All movement of molecules is directed by active transport. b. There is no movement of substances into and out of the cell. c. There is random movement of substances into and out of the cell. d. There is directed movement of substances into and out of the cell.

c

Which of these are NOT embedded in the hydrophobic portion of the lipid bilayer at all? a. integral proteins b. transmembrane proteins c. peripheral proteins d. All of these are embedded in the hydrophobic portion of the lipid bilayer.

c

For a protein to be an integral membrane protein, it would have to be _____. a. hydrophilic b. hydrophobic c. exposed on only one surface of the membrane d. amphipathic, with at least one hydrophobic region

d

What kinds of molecules pass through a cell membrane most easily? a.large polar b. ionic c. large and hydrophobic d. small and hydrophobic

d

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? a. Unsaturated fatty acids are more polar than saturated fatty acids. b. The double bonds block interaction among the hydrophilic head groups of the lipids. c. Unsaturated fatty acids have a higher cholesterol content and, therefore, more cholesterol in membranes. d. The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

d

A white blood cell engulfing a bacterium is an example of _____. a. receptor-mediated endocytosis b. pinocytosis c. facilitated diffusion d. exocytosis e. phagocytosis

e