19
Membrane Physiology
A. Multiple Choice
Key/
Page
No.
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a. mitochondria.
b. a cell membrane.
c. a cell wall.
d. a nucleus.
e. microtubules.
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c
3.
The lipid bilayer is held together mainly by
a. they have hydrophobic heads and hydrophilic tails.
b. they have polar heads and nonpolar tails.
c. they have polar tails and nonpolar heads.
d. the phospho-portion can form phosphodiester bonds between adjacent
phospholipids.
e. two of these.
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a. covalent bonding between membrane lipids.
b. hydrogen-bonding between the phospholipids’ tails.
c. repulsion between the phospholipids’ tails and water.
d. covalent bonding between the ends of phospholipids tails in opposite layers.
e. hydrogen-bonding between the head groups of the phospholipids.
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facing toward the aqueous environment and the ____ facing toward the interior of the
membrane.
a. bilayer, hydrophilic tails
b. bilayer, hydrophobic tails
c. micellar, hydrophilic tails
d. liposomal, hydrophilic tails
e. liposomal, hydrophobic tails
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a. reduces the permeability of gill membranes to water.
b. affects the activity of membrane proteins.
c. regulates membrane fluidity and stability.
d. two of these.
e. all of these.
b
All cells (not just animal cells) have
20
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a. Phospholipids will spontaneously form liposomes in nonpolar solvents.
b. A solution of pure fatty acids forms a lipid bilayer in a polar solvent.
c. Membrane lipids move laterally within their own layer.
d. Membrane lipids frequently move between one layer of the bilayer and the other.
e. The preferred form of a lipid bilayer in water is a flat sheet with exposed edges.
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FALSE?
a. Phospholipids with unsaturated tails make the bilayer more fluid because the
tails contain fewer hydrogens and thus form fewer hydrogen bonds with each
other.
b. Saturated phospholipids’ tails pack more tightly against each other than do
unsaturated tails.
c. Most membrane phospholipids have one fully saturated tail.
d. Phospholipid tails in a membrane can interact with each other via van der Waals
interactions.
e. Fatty acid tails vary in length.
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chains in the plasma membranes of its cells?
a. arctic fish
b. penguins
c. polar bears
d. tropical fish
e. pelicans
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a. as distinct layers with one layer facing the extracellular fluid and the other facing
the intracellular fluid.
b. both embedded in and associated with the lipid bilayer of the plasma membrane.
c. associated with the lipid bilayer of the plasma membrane, but not actually
embedded in it.
d. only in the plasma membrane, and not in other cellular membranes.
e. none of these.
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a. The plasma membrane is symmetrical (on average) around the plane between the
inner and outer halves.
b. The carbohydrate portion of glycoproteins is only found on the part of the protein
facing the cytoplasm.
c. The carbohydrate portion of glycoproteins is only found on the part of the protein
facing the extracellular fluid.
d. The carbohydrate portion of glycoproteins is found on both the extracellular
facing and intracellular facing part of the protein.
e. There are no glycoproteins in the plasma membrane.
c
6.
Which of the following statements regarding lipid membranes is true?
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membrane is FALSE?
a. Some membrane phospholipids form transmembrane channels that allow ion
movement.
b. The lipid bilayer defines the boundaries of the cell.
c. The lipid bilayer forms a permeability barrier to polar and charged substances.
d. The lipid bilayer confers fluidity to the plasma membrane.
e. All of the above statements are true.
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a. can exist in open or closed states.
b. are typically selective with respect to the types of substances that pass through
them.
c. can selectively repel particular ions.
d. all of these.
e. none of these.
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membrane lipids?
a. cholesterol
b. phospholipids
c. neutral lipids
d. polyunsaturated fatty acids.
e. none of these.
d
Which of the following pairs have NO relationship?
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a. hydrostatic pressure and osmosis.
b. osmotic pressure and osmosis.
c. osmotic pressure and colligative properties of solutes.
d. all of these pairs have a relationship.
e. none of these pairs has a relationship.
78 – 80
“cell” is placed into a solution of 6 mM CaCl2 and 6 mM NaCl.
a. The “cell” will be hypertonic to the surrounding solution.
b. The “cell” will be isotonic to the surrounding solution.
c. The “cell will be hypotonic to the surrounding solution.
d. The “cell” has a lower hydrostatic pressure than the surrounding solution.
e. Not enough information is provided to answer the question.
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a. carrier mediated transport or facilitated diffusion.
b. passive diffusion or active transport.
c. conduction or passive transport.
d. facilitated diffusion or active transport.
e. none of these.
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a membrane?
a. concentration gradient
b. cellular volume
c. permeability of the membrane to the diffusing substance
d. surface area across which diffusion is taking place
e. molecular weight of the diffusing substance
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a. using a carrier-mediated transport mechanism.
b. down a solute’s concentration gradient.
c. down its own concentration gradient.
d. across a membrane irrespective of concentration gradients.
e. across a membrane down its own concentration gradient.
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a. a measure of the concentration of solvent in a solution.
b. equal to the hydrostatic pressure required to oppose the movement of water into
a solution.
c. low in a solution with a high solute concentration.
d. dependent upon the lipid composition of the membrane.
e. two of these are correct.
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a. Tonicity refers to the effect of penetrating solutes on cell volume.
b. A one molal solution contains 1 mole of solute per liter of solution.
c. To accommodate larger molecules, membrane channels have an average diameter
of 1 – 1.5 nanometers.
d. Carrier proteins span the membrane and can undergo shape changes.
e. Aquaporins regulate solute movement across membranes.
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the extracellular medium by the cells until the extracellular concentration of choline
reaches 200 nM. At this concentration the curve levels off and the same rate of uptake is
seen at 200 and 225 nM extracellular choline. What has happened that can explain this
observation?
a. Cellular and extracellular choline concentrations are at equilibrium.
b. The transporters for choline saturate at 200 nM.
c. At choline concentrations of 200 nM and above, the osmotic pressure of the
cytoplasm prevents additional choline from entering the cell.
d. The cell cannot synthesis enough ATP to keep up with the energy demand of the
carrier.
e. None of these.
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that rates are faster when the experiments are carried out in a buffered, balanced salts
solution than when the experiments are carried out in a complete (containing all nutrients
required for survival and growth) medium. The most likely explanation for this
observation is
a. the concentration gradient for alanine is steeper in the former case than the latter.
b. the crenation (shrinkage of cells) in the salts solution increases the surface area–to–
volume ratio for the cells increasing the rate of diffusion.
c. the absence of amino acids in the balanced salts solution decreases the abundance
of molecules competing for transport, and therefore increases the apparent
transport rate.
d. the temperature of the balanced salt solution is higher, so rates of transport are
greater.
e. no response provides a valid answer.
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a. simple diffusion.
b. facilitated diffusion.
c. active transport.
d. There is not enough information given to distinguish between simple or
facilitated diffusion.
e. There is not enough information given to distinguish between facilitated
diffusion and active transport.
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a. Secondary active transport and cotransport carriers.
b. Symporters and cotransport carriers.
c. Na+-K+ pump and ouabain.
d. Caveolae and cell transport.
e. Osmosis and carrier mediated transport.
c
Which of the following is a NOT direct function of the Na+-K+ pump?
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a. development of a Na+ gradient across the cell membrane
b. development of a K+ gradient across the cell membrane
c. regulation of cellular pH
d. cell volume regulation
e. all of these are direct functions of this pump.
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their mother’s milk. This process requires the movement of intact antibodies from the
lumen of the intestine into the blood. This process involves a combination of
a. endocytosis.
b. exocytosis.
c. cotransport carriers.
d. endocytosis and cotransport carriers.
e. endocytosis and exocytosis.
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a. the uptake of substances through the activity of caveolae.
b. the specific uptake of tetrahydrocannabinol by facilitated diffusion.
c. the uptake of solid substances involving the formation of pseudopods.
d. the uptake of liquids through cellular drinking.
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paracrine signal?
a. It is an organic molecule.
b. It is not transported in the blood.
c. It affects the cell that released it.
d. Once released, it is distributed to its target(s) by simple diffusion.
e. It is released as a specific response to a signal.
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a. the chemical messenger.
b. the receptor for the chemical messenger.
c. the second messengers present in the cell.
d. the cell.
e. the organism.
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enzyme responsible for this phosphorylation would be classified as a __________ .
a. proteinase (or protease)
b. receptorase
c. phosphatase
d. kinase
e. ATPase
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F 3-19
messenger pathway?
a. cAMP → receptor → G-protein activation → PKA → phosphoproteins
b. receptor → G-protein activation → AC → cAMP → PKA → phosphoproteins
c. AC → decreased temperature → phospholipid-breakdown → cAMP → PKA →
phosphoproteins
d. G-protein activation → GDP → cGMP → cAMP → PKA → phosphoproteins
e. None of the above.
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97, 98
compared to a signaling pathway that utilizes the influx of ions is
a. the former are much faster in terms of generating cellular responses to first
messengers.
b. the former are slower in terms of generating cellular responses, allowing cells to
be more circumspect in their response to chemical signals.
c. the former require less first messenger to elicit a response, since they allow for
signal amplification.
d. the former require more first messenger to elicit a response, allowing for more
rapid termination of the signaling event.
e. none of these.
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Therefore, the cellular response to a steroid would be expected to include
a. an increase in mRNA produced from specific genes.
b. an increase in protein production, representing specific gene products.
c. both of these.
d. neither of these.
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contains 10 mM Na+ while chamber 2 contains 1 mM Na+. The membrane potential (1
relative to 2) in this scenario
a. is greater than 0 mV.
b. is equal to 0 mV.
c. is less than 0 mV.
d. cannot be determined based on the information given.
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a. the concentration gradient for potassium.
b. the charge gradient across the membrane.
c. the concentration gradient for sodium.
d. the action of the Na+-K+ pump.
e. none of these.
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a. Hormones are long distance signaling molecules.
b. Nanotubes allow the movement of organelles between adjacent cells.
c. Cytokines may act as small, long distance signaling molecules.
d. Paracrine signaling molecules are one type of chemical communication between
organisms.
e. Steroids are hydrophobic molecules derived from cholesterol.
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106,
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contains 10 mM NaCl and 1 mM KCl, and the second chamber contains 10 mM KCl and 1
mM NaCl. At equilibrium, the membrane potential (with chamber 1 relative to chamber
2) is
a. greater than 0 mV.
b. equal to 0 mV.
c. less than 0 mV.
d. unable to be determined without knowing the temperature.
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This is because
a. EK+ <<<< ENa+, and systems tend toward lower energy states.
b. cells like potassium better than sodium, so they work to maintain potassium
closer to its equilibrium distribution.
c. cell membranes are equally permeable to Na+ and Cl–, so every time a Na+ comes
in, its depolarizing effect is negated by a Cl– ion.
d. cell membranes are more permeable to K+ than Na+, so there are a greater number
of pathways available for K+ to move towards its equilibrium distribution than are
available for Na+ to do the same.
e. none of these.
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Which of the following is NOT a chemical structure category for signaling molecules?
a. retinoids
b. gases
c. pyrimidines
d. amines
e. peptides
e
40.
The equilibrium potential for most neurons is around -70mV. The maintenance of this
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potential is an example of
a. equilibrium.
b. homeostasis.
c. steady state.
d. both equilibrium and homeostasis.
e. both homeostasis and steady state.
B True or false
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77 membrane.
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84, 87
91
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91, 92 conduct.
97 adenylyl cyclase.
102
C. Matching (correct answers are aligned with each number; e.g., #1 matches with letter a)
D. Essay
Page No.
from the environment) of salmon gill epithelium, explain how increasing the number of
pumps helps the animal adjust to life in the sea.
plasma membrane fluidity and stability.
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body?
104 important in determining the membrane potential for a specific cell.
107 similar increase in extracellular sodium.