Mastering Biology - Prequiz Ch. 5

In oil-based liquids, phospholipids are arranged so that their _____ face outward and their _____ are orientated inward. a. hydrophobic tails ... hydrophilic heads b. hydrophilic heads ... hydrophobic tails c. hydrophobic heads ... hydrophilic tails d. hydrophilic tails ... hydrophobic heads

A

Phospholipids are well suited to be the main structural components of membranes because they _____. a. form a selectively permeable structure b. form a structure in which the hydrophobic portion faces outward c. are completely insoluble in water d. form a single sheet in water

A

If the volume of a cell increases when it is placed in an aqueous solution, that solution is said to be _____ to the cell. a. hypotonic b. hypertonic c. osmotic d. isotonic

a

The movement of molecules from an area of higher concentration to an area of lower concentration is called _____. a. diffusion b. phagocytosis c. active transport d. endocytosis

a

The diffusion of water across a selectively permeable membrane is called _____. a. osmosis b. active transport c. exocytosis d. facilitated diffusion

a. osmosis

The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? a. hypotonic sucrose solution b. hypertonic sucrose solution c. hypotonic urea solution d. hypertonic urea solution

b. hypertonic sucrose solution

Frequently, transplanted organs are rejected by the recipient's body. How is this reaction related to plasma membranes? a. The fibers of the extracellular matrix differ from individual to individual. b. Everyone's organs contain different amounts of cholesterol. c. Each person has a unique set of carbohydrate chains attached to his or her plasma membranes. d. The phospholipid bilayers become disrupted during transplant and may never re-form, causing the tissues to lose their function.

c. Each person has a unique set of carbohydrate chains attached to his or her plasma membranes.

The movement of atoms, ions, or molecules from a region of higher concentration to regions of lower concentration is called _____. a. crenation b. active transport c. spontaneous combustion d. diffusion

D

When water moves toward the solution with the _____ solute concentration, the solution is _____. a. greater ... hypertonic b. greater ... hypotonic c. lesser ... hypertonic d. greater ... isotonic

a

Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why? a. Molecules and active sites vary in size; only properly sized molecules can fit. b. There is a precise compatibility between the active site and the lactose molecule. c. Reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules. d. Specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.

b. There is a precise compatibility between the active site and the lactose molecule.

The plasma membrane is selectively permeable. Which of the following can pass freely through the membrane with no assistance? a. sodium and hydrogen ions b. oxygen and carbon dioxide c. starch and cellulose d. glucose and lactose

b. oxygen and carbon dioxide

Which of these statements about enzyme inhibitors is true? a. A noncompetitive inhibitor does not change the shape of the active site. b. A competitive inhibitor binds to the enzyme outside the active site. c. The action of competitive inhibitors may be reversible or irreversible. d. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback.

c

Seawater is dangerous to drink because _____. a. the salt causes hypertension and you will promptly die of a stroke b. seawater is isotonic to your body fluids and you will absorb too much water, causing your cells to burst c. one cup of seawater contains enough sodium to poison you d. seawater is hypertonic to your body tissues and drinking it will cause you to lose water by osmosis

d

Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____. a. actively pump salt back out of their cells to counter its inflow due to osmosis b. synthesize membranes that are impermeable to substances that upset osmotic balance c. actively pump water back out of their cells to counter its inflow due to osmosis d. actively pump water back into their cells to counter its loss due to osmosis

d. actively pump water back into their cells to counter its loss due to osmosis

When placed in a hypotonic environment, where the solute concentration is below that of the cell, a houseplant will _____. a. go limp and lifeless b. go brown at the edges of its leaves c. die d. remain standing upright

d. remain standing upright