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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
According to the fluid mosaic model of cell membranes, which of the following is a true statement about
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.
Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane
more fluid at lower temperatures?
a. Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes.
b. The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
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.
e. The double bonds result in shorter fatty acid tails and thinner membranes.
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.
Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is
a. by decreasing the number of hydrophobic proteins in the membrane
b. by increasing the percentage of cholesterol molecules in the membrane
c. by increasing the percentage of unsaturated phospholipids in the membrane
d. by cotransport of glucose and hydrogen
e. by using active transport
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. Only certain membranes are constructed from amphipathic molecules.
e. Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces
facing the cytoplasm.
A protein that spans the phospholipid bilayer one or more times is
a. a transmembrane protein.
b. an integral protein.
c. a peripheral protein.
d. an integrin.
e. a glycoprotein.
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
Which of the following amino acids would most likely be present in the transmembrane domain of an integral
a. a charged amino acid like lysine
b. a polar amino acid like serine
c. a special amino acid like glycine or proline
d. a hydrophobic amino acid like valine
e. any of the above, with no preference
In a paramecium (a single-celled eukaryote), cell surface integral membrane proteins are synthesized
a. in the cytoplasm by free ribosomes.
b. by ribosomes in the nucleus.
c. by ribosomes bound to the rough endoplasmic reticulum.
d. by ribosomes in the Golgi vesicles.
e. by ribosomes bound to the inner surface of the plasma membrane.
The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell
a. to facilitate diffusion of molecules down their concentration gradients.
b. to actively transport molecules against their concentration gradients.
c. to maintain the integrity of a fluid mosaic membrane.
d. to maintain membrane fluidity at low temperatures.
e. to mediate cell-to-cell recognition.
What kinds of molecules pass through a cell membrane most easily?
a. large and hydrophobic
b. small and hydrophobic
c. large polar
e. monosaccharides such as glucose
Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?
b. an amino acid
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.
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.
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
d. It is an active process (requires expenditure of energy by the cell) in which molecules move from a region of
lower concentration to one of higher concentration.
e. It requires integral proteins in the cell membrane.
Which of the following processes includes all others?
b. diffusion of a solute across a membrane
c. facilitated diffusion
d. passive transport
e. transport of an ion down its electrochemical gradient
Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?
a. The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution.
b. The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution.
c. The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution.
d. The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.
e. The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.
When a plant cell is submerged in a hypotonic solution, what is likely to occur?
a. The cell will burst.
b. The cell membrane will lyse.
c. Plasmolysis will shrink the interior.
d. The cell will become flaccid.
e. The cell will become turgid.
Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl.
What will happen if red blood cells are transferred to seawater?
a. Water will leave the cells, causing them to shrivel and collapse.
b. NaCl will be exported from the red blood cells by facilitated diffusion.
c. The blood cells will take up water, swell, and eventually burst.
d. NaCl will passively diffuse into the red blood cells.
e. The blood cells will expend ATP for active transport of NaCl into the cytoplasm.
A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled
water, equal to the volume of blood lost, is transferred directly into one of his veins. What will be the most
probable result of this transfusion?
a. It will have no unfavorable effect as long as the water is free of viruses and bacteria.
b. The patient's red blood cells will shrivel up because the blood fluid has become hypotonic compared to the cells.
c. The patient's red blood cells will swell because the blood fluid has become hypotonic compared to the cells.
d. The patient's red blood cells will shrivel up because the blood fluid has become hypertonic compared to the cells.
e. The patient's red blood cells will burst because the blood fluid has become hypertonic compared to the cells.
What is the voltage across a membrane called?
a. water potential
b. chemical gradient
c. membrane potential
d. osmotic potential
e. electrochemical gradient
The sodium-potassium pump is called an electrogenic pump because it
a. pumps equal quantities of Na+ and K+ across the membrane.
b. contributes to the membrane potential.
c. pumps hydrogen ions out of the cell.
d. ionizes sodium and potassium atoms.
e. is used to drive the transport of other molecules against a concentration gradient.
The movement of potassium into an animal cell against its concentration gradient requires
a. low cellular concentrations of sodium.
b. high cellular concentrations of potassium.
c. an energy source such as ATP.
d. a cotransport protein.
e. a potassium channel protein.
White blood cells engulf bacteria through what process?
e. receptor-mediated exocytosis
Once engulfed by a white blood cell, the bacterium will be digested by enzymes contained in the
b. Golgi vesicles.
d. secretory vesicles.
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
d. pinocytosis requires cellular energy, but receptor-mediated endocytosis does not.
e. pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.
Familial hypercholesterolemia is characterized by which of the following?
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
e. a general lack of glycolipids in the blood cell membranes
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