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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
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Certain proteins are unique to each membrane
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According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly ______
a) spread in a continuous layer over the inner and outer surfaces of the membrane
b) confined to the hydrophobic core of the membrane
c) embedded in a lipid bilayer
d) randomly oriented in the membrane, with no inside-outside polarity
e) free to depart from the fluid membrane and dissolve in the surrounding solution
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embedded in a lipid bilayer
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Which of the following factors would tend to increase membrane fluidity?
a) a greater proportion of unsaturated phospholipids
b) a greater proportion of saturated phospholipids
c) a lower temperature
d) a relatively high protein content in the membrane
e) a greater proportion of relatively large glycolipids compared with lipids having smaller molecule masses
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A greater proportion of unsaturated phospholipids
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Which of the following processes includes all others?
a) osmosis
b) diffusion of a solute across a membrane
c) facilitated diffusion
d) passive transport
e) transport of an ion down its electrochemical gradient
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passive transport
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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
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phospholipids and proteins
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peripheral proteins
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D
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cholesterol
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E
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fiber of the extracellular matrix
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A
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microfilament of the cytoskeleton
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C
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glycolipid
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B
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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.
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enables the membrane to stay fluid more easily when cell temperature drops
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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.
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They can move laterally along the plane of the membrane
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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
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by increasing the percentage of unsaturated phospholipids in the membrane
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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
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amphipathic
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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.
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The double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart
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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
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A cell’s ability to distinguish one type of neighboring cell from another
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Which of the following is true of integral membrane proteins?
A) They lack tertiary structure.
B) They are loosely bound to the surface of the bilayer.
C) They are usually transmembrane proteins.
D) They are not mobile within the bilayer.
E) They serve only a structural role in membranes.
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they are usually transmembrane proteins
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An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be
impaired in which function?
A) transporting ions against an electrochemical gradient
B) cell-cell recognition
C) maintaining fluidity of the phospholipid bilayer
D) attaching to the cytoskeleton
E) establishing the diffusion barrier to charged molecules
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cell-cell recognition
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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
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transmembrane proteins
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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
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peripheral proteins
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Which of these are attached to the extracellular matrix?
A) transmembrane proteins
B) integral proteins
C) peripheral proteins
D) integrins
E) glycoproteins
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integrins
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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
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glycoproteins
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Cell membranes are asymmetrical. Which of the following is a most likely explanation?
A) The cell membrane forms a border between one cell and another in tightly packed tissues such as
epithelium.
B) Cell membranes communicate signals from one organism to another.
C) Cell membrane proteins are determined as the membrane is being packaged in the ER and Golgi.
D) The ʺinnernessʺ and ʺouternessʺ of membrane surfaces are predetermined by genes.
E) Proteins can only span cell membranes if they are hydrophobic.
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Cell membrane proteins are determined as the membrane is being packaged in the ER and Golgi.
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Why are lipids and proteins free to move laterally in membranes?
A) The interior of the membrane is filled with liquid water.
B) There are no covalent bonds between lipid and protein in the membrane.
C) Hydrophilic portions of the lipids are in the interior of the membrane.
D) There are only weak hydrophobic interactions in the interior of the membrane.
E) Molecules such as cellulose can pull them in various directions.
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Hydrophilic portions of the lipids are in the interior of the membrane
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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
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small and hydrophobic
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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.
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It exhibits a specificity for a particular type of molecule
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After a membrane freezes and then thaws, it often becomes leaky to solutes. The most reasonable explanation
for this is that
A) transport proteins become nonfunctional during freezing.
B) the lipid bilayer loses its fluidity when it freezes.
C) aquaporins can no longer function after freezing.
D) the integrity of the lipid bilayer is broken when the membrane freezes.
E) the solubility of most solutes in the cytoplasm decreases on freezing.
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the integrity of the lipid bilayer is broken when the membrane freezes.
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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
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CO2
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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.
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It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
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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.
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it moves through aquaporins in the membrane
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Initially, in terms of tonicity, the solution in side A with respect to that in side B is
A) hypotonic.
B) plasmolyzed.
C) isotonic.
D) saturated.
E) hypertonic.
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isotonic
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After the system reaches equilibrium, what changes are observed?
A) The molarity of sucrose and glucose are equal on both sides.
B) The molarity of glucose is higher in side A than in side B.
C) The water level is higher in side A than in side B.
D) The water level is unchanged.
E) The water level is higher in side B than in side A.
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The water level is higher in side A than in side B
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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 patientʹs red blood cells will shrivel up because the blood fluid is hypotonic compared to the cells.
C) The patientʹs red blood cells will swell because the blood fluid is hypotonic compared to the cells.
D) The patientʹs red blood cells will shrivel up because the blood fluid is hypertonic compared to the cells.
E) The patientʹs red blood cells will burst because the blood fluid is hypertonic compared to the cells.
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The patients’ red blood cells will swell because the blood fluid is hyptonic compared to the cells
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Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a
salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are
A) hypotonic to both fresh water and the salt solution.
B) hypertonic to both fresh water and the salt solution.
C) hypertonic to fresh water but hypotonic to the salt solution.
D) hypotonic to fresh water but hypertonic to the salt solution.
E) isotonic with fresh water but hypotonic to the salt solution.
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hypertonic to fresh water but hypotonic to the salt solution
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A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing
0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms
describes the tonicity of the external solution relative to the cytoplasm of the cell?
A) turgid
B) hypertonic
C) hypotonic
D) flaccid
E) isotonic
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isotonic
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When a plant cell, such as one from a peony stem, is submerged in a very 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
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the cell will become turgid
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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
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Na+ ions moving out of the cell
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What are the membrane structures that function in active transport?
A) peripheral proteins
B) carbohydrates
C) cholesterol
D) cytoskeleton filaments
E) integral proteins
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integral proteins
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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
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facilitated diffusion
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What is the voltage across a membrane called?
A) water potential
B) chemical gradient
C) membrane potential
D) osmotic potential
E) electrochemical gradient
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membrane potential
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The sodium-potassium pump is called an electrogenic pump because it
A) pumps equal quantities of Na+ and K+ across the membrane.
B) pumps hydrogen ions out of the cell.
C) contributes to the membrane potential.
D) ionizes sodium and potassium atoms.
E) is used to drive the transport of other molecules against a concentration gradient.
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contributes to the membrane potential
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If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely true?
a) the sodium ions are moving down their electrochemical gradient while glucose is moving up
b) Glucose is entering the cel along its concentration gradient
c) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell
d) Potassium ions move aross the same gradient as sodium ions
e) A substance that blocked ions from binding to the cotransport protein would also block the transport of glucose
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e) A substance that blocked ions from binding to the cotransport protein would also block the transport of glucose
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The movement of potassium into an animal cell requires
A) low cellular concentrations of sodium.
B) high cellular concentrations of potassium.
C) an energy source such as ATP or a proton gradient.
D) a cotransport protein.
E) a gradient of protons across the plasma membrane
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an energy source such as ATP or a proton gradient
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Ions diffuse across membranes down their
A) chemical gradients.
B) concentration gradients.
C) electrical gradients.
D) electrochemical gradients.
E) A and B are correct.
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electrochemical gradients
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The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma
membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER
membrane will the ATP binding site be on?
A) It will be on the cytoplasmic side of the ER.
B) It will be on the side facing the interior of the ER.
C) It could be facing in either direction because the orientation of proteins is scrambled in the Golgi
apparatus.
D) It doesnʹt matter, because the pump is not active in the ER.
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It will be on the cytoplasmic side of the ER
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Proton pumps are used in various ways by members of every kingdom of organisms. What does this most
probably mean?
A) Proton pumps must have evolved before any living organisms were present on the earth.
B) Proton pumps are fundamental to all cell types.
C) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
D) Cells with proton pumps were maintained in each Kingdom by natural selection.
E) Proton pumps are necessary to all cell membranes.
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Cells with proton pumps were maintained in each Kingdom by natural selection
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Several seriously epidemic viral diseases of earlier centuries were then incurable because they resulted in
severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed
which of the following?
A) antiviral medications that are efficient and work well with all viruses
B) antibiotics against the viruses in question
C) intravenous feeding techniques
D) medication to prevent blood loss
E) hydrating drinks that include high concentrations of salts and glucose
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hydrating drinks that include high concentrations of salts and glucose
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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
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Phagocytosis
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White blood cells engulf bacteria through what process?
A) exocytosis
B) phagocytosis
C) pinocytosis
D) osmosis
E) receptor-mediated exocytosis
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phagocytosis
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The difference between pinocytosis and receptor-mediated endocytosis is that
A) pinocytosis brings only water 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 more selectivity.
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.
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pinocytosis brings only water into the cell, but receptor-mediated endocytosis brings in other molecules as well
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In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they
end up after endocytosis?
A) on the outside of vesicles
B) on the inside surface of the cell membrane
C) on the inside surface of the vesicle
D) on the outer surface of the nucleus
E) on the ER
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on the inside surface of the vesicle
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