Cell Membrane
12) According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? A) They can move laterally along the plane of the membrane. B) They frequently flip-flop from one side of the membrane to the other. C) They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. D) They are free to depart from the membrane and dissolve in the surrounding solution. E) They have hydrophilic tails in the interior of the membrane.
A.
13) Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold? A) by increasing the percentage of unsaturated phospholipids in the membrane B) by increasing the percentage of cholesterol molecules in the membrane C) by decreasing the number of hydrophobic proteins in the membrane D) by co-transport of glucose and hydrogen E) by using active transport
A.
16) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures? A) The double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart. B) Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes. C) Unsaturated fatty acids permit more water in the interior of the membrane. D) The double bonds block interaction among the hydrophilic head groups of the lipids. E) The double bonds result in shorter fatty acid tails and thinner membranes.
A.
21) Which of the following span the phospholipids bilayer, usually a number of times? A) transmembrane proteins B) integral proteins C) peripheral proteins D) integrins E) glycoproteins
A.
32) 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+ E) starch
A.
29) What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as glucose
B.
30) Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A) It is a peripheral membrane protein. B) It exhibits a specificity for a particular type of molecule. C) It requires the expenditure of cellular energy to function. D) It works against diffusion. E) It has few, if any, hydrophobic amino acids.
B.
14) In order for a protein to be an integral membrane protein it would have to be which of the following? A) hydrophilic B) hydrophobic C) amphipathic D) completely covered with phospholipids E) exposed on only one surface of the membrane
C.
22) Which of these are not embedded in the lipid bilayer at all? A) transmembrane proteins B) integral proteins C) peripheral proteins D) integrins E) glycoproteins
C.
33) Which of the following statements is correct about diffusion? A) It is very rapid over long distances. B) It requires an expenditure of energy by the cell. C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration. E) It requires integral proteins in the cell membrane.
C.
4) Which of the following types of molecules are the major structural components of the cell membrane? A) phospholipids and cellulose B) nucleic acids and proteins C) phospholipids and proteins D) proteins and cellulose E) glycoproteins and cholesterol
C.
52) Which of the following membrane activities require energy from ATP hydrolysis? A) facilitated diffusion. B) movement of water into a cell C) Na+ ions moving out of the cell D) movement of glucose molecules E) movement of water into a paramecium
C.
55) What is the voltage across a membrane called? A) water potential B) chemical gradient C) membrane potential D) osmotic potential E) electrochemical gradient
C.
23) Which of these are attached to the extracellular matrix? A) transmembrane proteins B) integral proteins C) peripheral proteins D) integrins E) glycoproteins
D.
65) An organism with a cell wall would have the most difficulty doing which process? A) diffusion B) osmosis C) active transport D) phagocytosis E) facilitated diffusion
D.
10) When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that A) the integral membrane proteins are not strong enough to hold the bilayer together. B) water that is present in the middle of the bilayer freezes and is easily fractured. C) hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing. D) the carbon-carbon bonds of the phospholipid tails are easily broken. E) the hydrophobic interactions that hold the membrane together are weakest at this point.
E.
11) The presence of cholesterol in the plasma membranes of some animals A) enables the membrane to stay fluid more easily when cell temperature drops. B) enables the animal to remove hydrogen atoms from saturated phospholipids. C) enables the animal to add hydrogen atoms to unsaturated phospholipids. D) makes the membrane less flexible, allowing it to sustain greater pressure from within the cell. E) makes the animal more susceptible to circulatory disorders.
E.
18) Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes? A) facilitated diffusion of molecules down their concentration gradients B) active transport of molecules against their concentration gradients C) maintaining the integrity of a fluid mosaic membrane D) maintaining membrane fluidity at low temperatures E) a cellʹs ability to distinguish one type of neighboring cell from another
E.
20) In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model? A) The membrane is only fluid across a very narrow temperature range. B) Proteins rarely move, even though they possibly can do so. C) Unsaturated lipids are excluded from the membranes. D) The concentration of protein molecules is now known to be much higher. E) The proteins are known to be made of only acidic amino acids.
E.
24) Which of these often serve as receptors or cell recognition molecules on cell surfaces? A) transmembrane proteins B) integral proteins C) peripheral proteins D) integrins E) glycoproteins
E.
34) Water passes quickly through cell membranes because A) the bilayer is hydrophilic. B) it moves through hydrophobic channels. C) water movement is tied to ATP hydrolysis. D) it is a small, polar, charged molecule. E) it moves through aquaporins in the membrane.
E.
53) What are the membrane structures that function in active transport? A) peripheral proteins B) carbohydrates C) cholesterol D) cytoskeleton filaments E) integral proteins
E.
54) 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? A) simple diffusion B) phagocytosis C) active transport pumps D) exocytosis E) facilitated diffusion
E.