Chapter 8

C

1) For a protein to be an integral membrane protein, it would have to be _____. A) hydrophilic B) hydrophobic C) amphipathic, with at least one hydrophobic region D) exposed on only one surface of the membrane

A

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in _____. A) lysosomes B) Golgi vesicles C) vacuoles D) secretory vesicles

A

According to the fluid mosaic model of cell membranes, phospholipids _____. A) can move laterally along the plane of the membrane B) frequently flip-flop from one side of the membrane to the other C) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane D) have hydrophilic tails in the interior of the membrane

B

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? A) transporting ions against an electrochemical gradient B) cell-cell recognition C) attaching the plasma membrane to the cytoskeleton D) establishing a diffusion barrier to charged molecules

C

An organism with a cell wall would most likely be unable to take in materials through _____. A) osmosis B) active transport C) phagocytosis D) facilitated diffusion

C

Diffusion _____. A) is very rapid over long distances B) requires an expenditure of energy by the cell C) is a passive process in which molecules move from a region of higher concentration to a region of lower concentration D) requires integral proteins in the cell membrane

A

Familial hypercholesterolemia is characterized by _____. A) defective LDL receptors on the cell membranes B) poor attachment of the cholesterol to the extracellular matrix of cells C) a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes D) inhibition of the cholesterol active transport system in red blood cells

C

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis? A) on the outside of vesicles B) on the inside surface of the cell membrane C) on the inside surface of the vesicle D) on the outer surface of the nucleus

B

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) Only certain membranes of the cell are selectively permeable. D) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.

B

In which of the following would there be the greatest need for osmoregulation? A) an animal connective tissue cell bathed in isotonic body fluid B) a salmon moving from a river into an ocean C) a red blood cell surrounded by plasma D) a plant being grown hydroponically in a watery mixture of designated nutrients

B

Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At higher temperatures, these regions _____. A) are more fluid than the surrounding membrane B) are less fluid than the surrounding membrane C) detach from the plasma membrane and clog arteries D) have higher rates of lateral diffusion of lipids and proteins into and out of these regions

B

What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic

A

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

D

When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution, what is likely to occur? A) The cell will burst. B) Plasmolysis will shrink the interior. C) The cell will become flaccid. D) The cell will become turgid.

D

Which of the following allows water to move much faster across cell membranes? A) the sodium-potassium pump B) ATP C) peripheral proteins D) aquaporins

A

Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A) It exhibits a specificity for a particular type of molecule. B) It requires the expenditure of cellular energy to function. C) It works against diffusion. D) It has no hydrophobic regions.

A

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

C

Which of the following is true of osmosis? A) Osmosis only takes place in red blood cells. B) Osmosis is an energy-demanding or "active" process. C) In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration. D) In osmosis, solutes move across a membrane from areas of lower water concentration to areas of higher water concentration.

D

Which of the following most accurately describes selective permeability? A) An input of energy is required for transport. B) Lipid-soluble molecules pass through a membrane. C) There must be a concentration gradient for molecules to pass through a membrane. D) Only certain molecules can cross a cell membrane.

C

Which of the following processes includes all others? A) osmosis B) facilitated diffusion C) passive transport D) transport of an ion down its electrochemical gradient

A

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? A) CO2 B) an amino acid C) glucose D) K+

C

Which of these are NOT embedded in the hydrophobic portion of the lipid bilayer at all? A) transmembrane proteins B) integral proteins C) peripheral proteins D) All of these are embedded in the hydrophobic portion of the lipid bilayer.

A

White blood cells engulf bacteria using _____. A) phagocytosis B) pinocytosis C) osmosis D) receptor-mediated exocytosis

D

Why are lipids and proteins free to move laterally in membranes? A) The interior of the membrane is filled with liquid water. B) Lipids and proteins repulse each other in the membrane. C) Hydrophilic portions of the lipids are in the interior of the membrane. D) There are only weak hydrophobic interactions in the interior of the membrane.

A

You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose? A) Permeability to glucose will increase. B) Permeability to glucose will decrease. C) Permeability to glucose will stay the same. D) You cannot predict the outcome. You simply have to make the measurement.