BIOS 1404 MT 2 Key - A) They lack tertiary structure. B) They are lo...

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BIOS 1404 MT 2 Key

• Which of the following is true of integral membrane proteins?
• They lack tertiary structure.
• They are loosely bound to the surface of the bilayer.
• They are usually transmembrane proteins.
• They are not mobile within the bilayer.
• They serve only a structural role in membranes.

–Answer C

• What kinds of molecules pass through a cell membrane most easily?
• large and hydrophobic
• small and hydrophobic
• large polar
• ionic
• monosaccharides such as glucose

–Answer B

• Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small

intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

• simple diffusion
• phagocytosis
• active transport pumps
• exocytosis
• facilitated diffusion

–Answer E

• The phosphate transport system in bacteria imports phosphate into the cell even when the

concentration of 1 / 3

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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.Phosphate transport is an example of

• passive diffusion.
• facilitated diffusion.
• active transport.
• osmosis.
• cotransport.

–Answer E

• Ions diffuse across membranes through specific ion channels
• down their chemical gradients.
• down their concentration gradients.
• down the electrical gradients.

• down their electrochemical gradients.
• down their osmotic potential gradient

–Answer D

• Which of the following most likely would be an immediate result of a growth factor

binding to its receptor?

• G protein activation
• adenylyl cyclase activity
• GTPase activity
• protein phosphatase activity
• phosphorylase activity

–Answer A

• Which of the following is a correct association?
• kinase activity and the addition of a tyrosine
• phosphodiesterase activity and the removal of phosphate groups
• GTPase activity and hydrolysis of GTP to GDP 2 / 3

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• phosphorylase activity and the catabolism of glucose
• adenylyl cyclase activity and the conversion of cAMP to AMP

–Answer C

• Which of the following is a reasonable explanation for why unsaturated fatty acids help

keep any membrane more fluid at lower temperatures?

• The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from

packing tightly.

• Unsaturated fatty acids have a higher cholesterol content and therefore more

cholesterol in their membranes.

• Unsaturated fatty acids are more polar than saturated fatty acids.
• The double bonds block interaction among the hydrophilic head groups of the lipids.
• The double bonds result in shorter fatty acid tails and thinner membranes

–Answer A

• Which of the following statements is correct about diffusion?
• It is very rapid over long distances.
• It requires an expenditure of energy by the cell.
• It is a passive process in which molecules move from a region of higher concentration

to a region of lower concentration.

• It is an active process in which molecules move from a region of lower concentration

to one of higher concentration.

• It requires integral proteins in the cell membrane.

–Answer C

• When a plant cell, such as one from a peony stem, is submerged in a very hypotonic

solution, what is likely to occur?

• The cell will burst.
• The cell membrane will lyse.
• Plasmolysis will shrink the interior.
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