Chapter 7

Which of the following is a major difference between prokaryotic and eukaryotic cells? Prokaryotic cells have no phospholipids; eukaryotic cells do. Prokaryotic cells have no DNA; eukaryotic cells have DNA. Eukaryotic cells have a plasma membrane, whereas prokaryotic cells do not. Most prokaryotic cells have no internal membranes; eukaryotic cells do.

Most prokaryotic cells have no internal membranes; eukaryotic cells do

Which of the following would likely diffuse through the lipid bilayer of a plasma membrane most rapidly? O2 Na+ sucrose an amino acid

O2

How do membrane phospholipids interact with water? They have hydrophilic tails that face outward and are exposed to water and hydrophobic heads that face the center of the membrane and are shielded from water. The polar heads repel water and the nonpolar tails attract water. Phospholipids do not interact with water because they are lipids, and thus are hydrophobic. The polar heads interact with water; the nonpolar tails do not.

The polar heads interact with water; the nonpolar tails do not

Which factors affect the rate of osmotic movement of water? The rate of osmosis increases with increasing differences in solute concentrations between two solutions separated by a selectively permeable membrane. Hydrostatic pressure applied to a hypertonic solution separated from a hypotonic solution by a selectively permeable membrane increases osmotic movement across the membrane. No factors have an effect; the rate of osmosis is constant.

The rate of osmosis increases with increasing differences in solute concentrations between two solutions separated by a selectively permeable membrane

The force driving simple diffusion is ________, while the energy source for active transport is ________. transmembrane pumps; an electrochemical gradient a concentration gradient; ATP hydrolysis phosphorylated carrier proteins; ATP a concentration gradient; ADP

a concentration gradient; ATP hydrolysis

Which of the following factors would tend to increase membrane fluidity? a greater proportion of saturated phospholipids a greater proportion of unsaturated phospholipids a lower temperature a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses a relatively high protein content in the membrane

a greater proportion of unsaturated phospholipids

Which of the following structures would decrease the electrochemical gradient across a membrane? a potassium channel an aquaporin a proton pump both a proton pump and a sodium channel

a potassium channel

In which of the following environments would there be the greatest need for osmoregulation? a red blood cell surrounded by plasma an animal connective tissue cell bathed in isotonic body fluid a salmon moving from a river into an ocean a plant being grown hydroponically in a watery mixture of designated nutrients

a salmon moving from a river into an ocean

Which of the following statements is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? Sodium and glucose compete for the same binding site in the cotransporter. Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose. Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.

a substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose

If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol? passive transport diffusion active transport osmosis facilitated diffusion

active transport

Active and passive transport of solutes across a membrane typically differ in which of the following ways? Active transport is always faster than passive transport. Active transport is used for ions, passive transport is used for uncharged solutes. Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy. Active transport is usually down the concentration gradient of the solute, whereas passive transport is always against the concentration gradient of the solute. Active transport uses protein carriers, whereas passive transport uses carbohydrate carriers.

active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy

For a protein to be an integral membrane protein, it would have to be _____. amphipathic, with at least one hydrophobic region hydrophobic exposed on only one surface of the membrane hydrophilic

amphipathic, with at least one hydrophobic region

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? The animal cell is in _____. an isotonic solution, and the plant cell is in a hypotonic solution a hypertonic solution, and the plant cell is in an isotonic solution an isotonic solution, and the plant cell is in a hypertonic solution a hypotonic solution, and the plant cell is in an isotonic solution

an isotonic solution, and the plant cell is in a hypotonic solution

Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes? aquaporins the sodium-potassium pump ATP gated ion channels

aquaporins

In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane? They are synthesized ________. by ribosomes in the rough ER, secreted from the cell, and inserted into the plasma membrane from the outside on ribosomes on the plasma membrane by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of secretory vesicles on free cytoplasmic ribosomes and then inserted into the plasma membrane

by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of secretory vesicles

According to the fluid mosaic model of cell membranes, phospholipids _____. frequently flip-flop from one side of the membrane to the other can move laterally along the plane of the membrane have hydrophilic tails in the interior of the membrane occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane

can move laterally along the plane of the membrane

An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function? transporting ions against an electrochemical gradient establishing a diffusion barrier to charged molecules attaching the plasma membrane to the cytoskeleton cell-cell recognition

cell-cell recognition

In what way do membranes vary among eukaryotic cells? Phospholipids are found only in certain membranes. Only certain membranes of the cell are selectively permeable. Certain proteins are unique to each membrane. Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm. Only certain membranes are constructed from amphipathic molecules.

certain membranes are unique to each membrane

In what way do the membranes of a eukaryotic cell vary? Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm. Only certain membranes of the cell are selectively permeable. Phospholipids are found only in certain membranes. Certain proteins are unique to each membrane.

certain proteins are unique to each membrane

Which of the following types of molecules lack hydrophilic domains? cholesterol transmembrane proteins peripheral membrane proteins integral membrane proteins

cholesterol

In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by _____. cotransport proteins pores in the plasma membrane ion channels passive diffusion across the plasma membrane

contransport proteins

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membranemore acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of ________. cotransport facilitated diffusion passive diffusion active transport

cotransport

The movement of glucose into a cell against a concentration gradient is most likely to be accomplished by which of the following? movement of glucose into the cell through a glucose channel facilitated diffusion of the glucose using a carrier protein cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis passive diffusion of the glucose through the lipid bilayer receptor-mediated endocytosis

cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis

Which of the following is least likely to be important in holding the components of a biological membrane together? covalent interactions between the phospholipid and protein components of the membrane polar interactions among the phospholipid head groups on the same surface of the membrane hydrophobic interactions among the fatty acid tails of phospholipids on opposite sides of the membrane hydrophobic interactions among the fatty acid tails of phospholipids on the same side of the membrane hydrophobic interactions between the phospholipid tails and the surface of integral membrane proteins buried in the membrane

covalent interactions between the phospholipid and protein components of the membrane

Based on Figure 7.18 in your textbook, which of these experimental treatments would increase the rate of sucrose transport into the cell? decreasing cytoplasmic pH decreasing extracellular pH adding a substance that makes the membrane more permeable to hydrogen ions adding an inhibitor that blocks the regeneration of ATP decreasing extracellular sucrose concentration

decreasing extracellular pH

Familial hypercholesterolemia is characterized by _____. defective LDL receptors on the cell membranes a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes poor attachment of the cholesterol to the extracellular matrix of cells inhibition of the cholesterol active transport system in red blood cells

defective LDL receptors on the cell membranes

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly confined to the hydrophobic interior of the membrane. embedded in a lipid bilayer. free to depart from the fluid membrane and dissolve in the surrounding solution. spread in a continuous layer over the inner and outer surfaces of the membrane. randomly oriented in the membrane, with no fixed inside-outside polarity.

embedded in a lipid bilayer

Which of the following correctly describes some aspect of exocytosis or endocytosis? Endocytosis and exocytosis involve passive transport. Both processes provide a mechanism for exchanging membrane-impermeable molecules between the organelles and the cytosol. The inner surface of a transport vesicle that fuses with or buds from the plasma membrane is most closely related to the inner surface of the plasma membrane. These two processes require the participation of mitochondria. Exocytosis and endocytosis temporarily change the surface area of the plasma membrane.

exocytosis and endocytosis temporarily change the surface area of the plasma membrane

The sodium-potassium pump is called an electrogenic pump because it ________. generates voltage across the membrane decreases the voltage difference across the membrane pumps equal quantities of Na+ and K+ across the membrane in opposite directions is used to drive the transport of glucose against a concentration gradient

generates voltage across the membrane

Several epidemic microbial diseases of earlier centuries incurred high death rates 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 types of treatments? medications to slow blood loss hydrating drinks with high concentrations of salt and glucose intravenous feeding techniques antiviral medications that are efficient and work well with most viruses

hydrating drinks with high concentrations of salt and glucose

Which of the following statements correctly describes osmosis? Osmosis only takes place in red blood cells. Osmosis is an energy-demanding or "active" process. In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration. In osmosis, solutes move across a membrane from areas of lower water concentration to areas of higher water concentration.

in osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________. increasing the proportion of unsaturated phospholipids in the membrane decreasing the number of hydrophobic proteins in the membrane decreasing the percentage of cholesterol molecules in the membrane increasing the proportion of glycolipids in the membrane

increasing the proportion of unsaturated phospholipids in the membrane

Diffusion of ions across membranes through specific ion channels is driven by ________. ion concentration gradients only electrical gradients only active transport pumps ion electrochemical gradients

ion electrochemical gradients

According to the fluid mosaic model, a membrane ________. is composed of a mosaic of fluid polysaccharides and amphipathic proteins is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins

is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins

Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water_____. is hypotonic and the salt solution is hypertonic to the cells of the celery stalks and the salt solution are both hypertonic to the cells of the celery stalks is isotonic and the salt solution is hypertonic to the cells of the celery stalks is hypertonic and the salt solution is hypotonic to the cells of the celery stalks

is hypotonic and the salt solution is hypertonic to the cells of the celery stalks

Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane? It exhibits specificity for a particular type of molecule. It requires the expenditure of cellular energy to function. It has no hydrophobic regions. It works against diffusion.

it exhibits specificity for a particular type of molecule

Which of the following statements about diffusion is true? 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 a region of higher concentration. It requires an expenditure of energy by the cell. It is very rapid over long distances.

it is passive process in which molecules move from a region of higher concentration to a region of lower concentration

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in _____. secretory vesicles lysosomes Golgi vesicles vacuoles

lysosomes

The voltage across a membrane is called the _____. membrane potential electrochemical gradient osmotic potential chemical gradient

membrane potential

Which of the following membrane activities requires energy from ATP hydrolysis? movement of carbon dioxide out of a paramecium movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell facilitated diffusion of chloride ions across the membrane through a chloride channel movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

A sodium-potassium pump ________. moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis moves three potassium ions out of a cell and two sodium ions into a cell using energy from ATP hydrolysis moves three potassium ions out of a cell and two sodium ions into a cell while producing ATP for each cycle move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle

moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis

Hydrophobic substances like salad oil are polar molecules that repel water molecules. polar molecules that have an affinity for water because they contain many hydrogens that can form hydrogen bonds with water. nonpolar molecules that repel water molecules. nonpolar molecules that have an affinity for water because they contain many hydrogens that can form hydrogen bonds with water.

nonpolar molecules that repel water molecules

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis? on the inside surface of the vesicle on the inside surface of the cell membrane on the outer surface of the nucleus on the outside of vesicles

on the inside surface of the vesicle

Select the correct statement about osmosis. Osmosis is the diffusion of water molecules across a selectively permeable membrane. Osmotic equilibrium cannot be reached unless solute concentrations equalize across the membrane. If a dead cell is placed in a solution hypotonic to the cell contents, osmosis will not occur.

osmosis is the diffusion of water molecules across a selectively permeable membrane

Which of the following processes includes all of the others? transport of an ion down its electrochemical gradient passive transport facilitated diffusion osmosis

passive transport

Which of the following processes includes all others? passive transport facilitated diffusion transport of an ion down its electrochemical gradient diffusion of a solute across a membrane osmosis

passive transport

Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer? peripheral membrane proteins integral membrane proteins transmembrane proteins cholesterol

peripheral membrane proteins

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose? Permeability to glucose will increase. Permeability will decrease initially then increase as the bilayer fills with glucose. Permeability to glucose will decrease. Permeability to glucose will stay the same.

permeability to glucose will increase

An organism with a cell wall would most likely be unable to take in materials through _____. facilitated diffusion phagocytosis active transport osmosis

phagocytosis

White blood cells engulf bacteria using _____. receptor-mediated exocytosis phagocytosis pinocytosis osmosis

phagocytosis

The difference between pinocytosis and receptor-mediated endocytosis is that _____. pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area. pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well. pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot. pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity

When a plant cell, such as one from a tulip leaf, is submerged in a hypertonic solution, what is likely to occur? The cell will burst. Plasmolysis will shrink the interior of the cell. The cell will become turgid. The cell will become flaccid.

plasmolysis will shrink the interior of the cell

Which of the following statements is true regarding potential energy? Matter has a natural tendency to acquire more potential energy until a maximum is reached. Water acquires potential energy as it runs downhill. Potential energy is the energy possessed by matter due to its location or structure. Potential energy is the energy matter could have if it were in a different location or structure.

potential energy is the energy possessed by matter due to its location or structure

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this fact most probably mean? Cells of each domain evolved proton pumps independently when oceans became more acidic. Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life. Proton pumps are necessary to all cell membranes. The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.

proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life

A research team is working on the design of a new drug for the treatment of lung cancer. To be most effective, this drug must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug? specificity of the drug molecule for binding to the extracellular matrix of lung cells phospholipid composition of lung cell plasma membranes similarity of the drug molecule to other molecules normally transported lung cells the relative hydrophobicity of the drug molecule

similarity of the drug molecule to other molecules normally transported lung cells

What kinds of molecules pass through a cell membrane most easily? large polar large and hydrophobic small and ionic small and hydrophobic

small and hydrophobic

Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane? small hydrophobic molecules small ions large hydrophobic molecules carbon dioxide

small ions

What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water? The cell would shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC. The cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. The cell will remain the same size because the solution outside the cell is isotonic.

the cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC

Which statement is correct? A solution of seawater is hypertonic. The contents of a red blood cell are hyperosmotic to distilled water. A solution of distilled water is hypotonic.

the contents of a red blood cell are hyperosmotic

Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. The double bonds block interaction among the hydrophilic head groups of the lipids. Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly. Unsaturated fatty acids are more nonpolar than saturated fatty acids.

the double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly

A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water equal to the volume of blood lost is added to the blood directly via one of his veins. What will be the most probable result of this transfusion? The patient's red blood cells will shrivel up because the blood has become hypotonic compared to the cells. The patient's red blood cells will burst because the blood has become hypertonic compared to the cells. The patient's red blood cells will shrivel up because the blood has become hypertonic compared to the cells. The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.

the patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells

Which of the following statements about osmosis is correct? If a cell is placed in an isotonic solution, more water will enter the cell than leaves the cell. The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis. If a solution outside the cell is hypertonic compared to the cytoplasm, water will move into the cell by osmosis. Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration. Osmotic movement of water into a cell would likely occur if the cell accumulates water from its environment.

the presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis

What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane? A spot of red fluorescence will be visible on the infected cell's plasma membrane, marking the site of membrane fusion and HIV entry. A spot of red fluorescence will remain outside the cell after delivering the viral capsid. The red fluorescent dye-labeled lipids will appear in the infected cell's interior. A spot of red fluorescence will diffuse in the infected cell's cytoplasm.

the red fluorescent dye-labeled lipids will appear in the infected cell's interior

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical. Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature. The two sides of a cell membrane face different environments and carry out different functions. Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical.

the two sides of a cell membrane face different environments and carry out different functions

Which of the following statements about a typical plasma membrane is correct? Carbohydrates on the membrane surface are important in determining the overall bilayer structure. Phospholipids are the primary component that determines which solutes can cross the plasma membrane. The two sides of the plasma membrane have different lipid and protein composition. The hydrophilic interior of the membrane is composed primarily of the fatty acid tails of the phospholipids. The plasma membrane is a covalently linked network of phospholipids and proteins that controls the movement of solutes into and out of a cell.

the two sides of the plasma membrane have different lipid and protein composition

The permeability of a biological membrane to a specific polar solute depends primarily on which of the following? the amount of cholesterol in the membrane the types of transport proteins in the membrane the phospholipid composition of the membrane the presence of unsaturated fatty acids in the membrane the types of polysaccharides present in the membrane

the types of transport proteins in the membrane

Why are lipids and proteins free to move laterally in membranes? Lipids and proteins repulse each other in the membrane. The interior of the membrane is filled with liquid water. Hydrophilic portions of the lipids are in the interior of the membrane. There are only weak hydrophobic interactions in the interior of the membrane.

there are only weak hydrophobic interactions in the interior of the membrane

When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane? There is directed movement of substances into and out of the cell. All movement of molecules across the plasma membrane occurs by active transport. There is no movement of substances into or out of the cell. There is random movement of substances into and out of the cell.

there is random movement of substances into and out of the cell

In facilitated diffusion, what is the role of the transport protein? Transport proteins organize the phospholipids to allow the solute to cross the membrane. Transport proteins provide a protein site for ATP hydrolysis, which facilitates the movement of a solute across a membrane. Transport proteins provide a hydrophilic route for the solute to cross the membrane. Transport proteins provide a low-resistance channel for water molecules to cross the membrane. Transport proteins provide the energy for diffusion of the solute.

transport proteins provide a hydrophilic route for the solute to cross the membrane

Which of the following best describes the structure of a biological membrane? a fluid structure in which phospholipids and proteins move freely between sides of the membrane two layers of phospholipids with proteins either crossing the layers or on the surface of the layers two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot two layers of phospholipids with proteins embedded between the two layers

two layers of phospholipids with proteins either crossing the layers or on the surface of the layers

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium? Water molecules continue to move from the hypotonic solution to the hypertonic solution. Water molecules move between the two solutions, but there is no net movement of water across the membrane. Water molecules no longer move between the solutions.

water molecules move between the two solutions, but there is no net movement of water across the membrane

Which of the following molecular movements is due to diffusion or osmosis? The sodium-potassium pump pumps three sodium ions out of a neuron for every two potassium ions it pumps in. When a plant cell is placed in concentrated salt water, water moves out of the cell. Cells of the pancreas secrete insulin into the bloodstream.

when a plant cell is placed in concentration salt water, water moves out of the cell