AP Bio Chapter 7
Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane? A) It exhibits specificity for a particular type of molecule. B) It requires the expenditure of cellular energy to function. C) It works against diffusion. D) It has no hydrophobic regions.
A) It exhibits specificity for a particular type of molecule.
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? A) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life. B) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism. C) Cells of each domain evolved proton pumps independently when oceans became more acidic. D) Proton pumps are necessary to all cell membranes.
A) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains
Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. B) Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly. C) Unsaturated fatty acids are more nonpolar than saturated fatty acids. D) The double bonds block interaction among the hydrophilic head groups of the lipids.
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
According to the fluid mosaic model of cell membranes, phospholipids ________. A) can move laterally along the plane of the membrane B) frequently flip-flop from one side of the membrane to the other C) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane D) have hydrophilic tails in the interior of the membrane
A) can move laterally along the plane of the membrane
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 ________. A) cotransport proteins B) ion channels C) pores in the plasma membrane D) passive diffusion across the plasma membrane
A) cotransport proteins
Familial hypercholesterolemia is characterized by ________. 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
A) defective LDL receptors on the cell membranes
The membranes of winter wheat are able to remain fluid when it is extremely cold by ________. A) increasing the proportion of unsaturated phospholipids in the membrane B) decreasing the percentage of cholesterol molecules in the membrane C) decreasing the number of hydrophobic proteins in the membrane D) increasing the proportion of glycolipids in the membrane
A) increasing the proportion of unsaturated phospholipids in the membrane
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in ________. A) lysosomes B) Golgi vesicles C) vacuoles D) secretory vesicles
A) lysosomes
White blood cells engulf bacteria using ________. A) phagocytosis B) pinocytosis C) osmosis D) receptor-mediated exocytosis
A) phagocytosis
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) Some membranes have hydrophobic surfaces exposed to the cytoplasm while others have hydrophilic surfaces facing the cytoplasm.
B) Certain proteins are unique to each membrane.
A patient was involved 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? A) The patients red blood cells will shrivel up because the blood has become hypotonic compared to the cells. B) The patients red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells. C) The patients red blood cells will shrivel up because the blood has become hypertonic compared to the cells. D) The patients red blood cells will burst because the blood has become hypertonic compared to the cells.
B) The patients red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.
When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane? A) There is directed movement of substances into and out of the cell. B) There is random movement of substances into and out of the cell. C) There is no movement of substances into or out of the cell. D) All movement of molecules across the plasma membrane occurs by active transport.
B) There is random movement of substances into and out of the cell.
The force driving simple diffusion is ________, while the energy source for active transport is ________. A) a concentration gradient; ADP B) a concentration gradient; ATP hydrolysis C) transmembrane pumps; an electrochemical gradient D) phosphorylated carrier proteins; ATP
B) a concentration gradient; ATP hydrolysis
In which of the following environments would there be the greatest need for osmoregulation? A) an animal connective tissue cell bathed in isotonic body fluid B) a salmon moving from a river into an ocean C) a red blood cell surrounded by plasma D) a plant being grown hydroponically in a watery mixture of designated nutrients
B) a salmon moving from a river into an ocean
Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes? A) the sodium-potassium pump B) aquaporins C) gated ion channels D) ATP
B) aquaporins
An animal cell lacking carbohydrates 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) attaching the plasma membrane to the cytoskeleton D) establishing a diffusion barrier to charged molecules
B) cell-cell recognition
The sodium-potassium pump is called an electrogenic pump because it ________. A) pumps equal quantities of Na+ and K+ across the membrane in opposite directions B) is used to drive the transport of glucose against a concentration gradient C) decreases the voltage difference across the membrane D) generates voltage across the membrane
B) is used to drive the transport of glucose against a concentration gradient
The voltage across a membrane is called the ________. A) chemical gradient B) membrane potential C) osmotic potential D) electrochemical gradient
B) membrane potential
Which of the following membrane activities requires energy from ATP hydrolysis? A) facilitated diffusion of chloride ions across the membrane through a chloride channel B) movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid C) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell D) movement of carbon dioxide out of a paramecium
B) movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
A sodium-potassium pump ________. A) moves three potassium ions out of a cell and two sodium ions into a cell while producing ATP for each cycle B) moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis C) moves three potassium ions out of a cell and two sodium ions into a cell using energy from ATP hydrolysis D) move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle
B) moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis
What is the condition of a red blood cell if it has been placed in a hypotonic solution?
Bursting/cytolysis
Which of the following statements correctly describes osmosis? A) Osmosis only takes place in red blood cells. B) Osmosis is an energy-demanding or "active" process. C) In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration. D) In osmosis, solutes move across a membrane from areas of lower water concentration to areas of higher water concentration.
C) In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
Which of the following would likely diffuse through the lipid bilayer of a plasma membrane most rapidly? A) sucrose B) an amino acid C) O2 D) Na+
C) O2
Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? A) Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical. B) Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical. C) The two sides of a cell membrane face different environments and carry out different functions. D) Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature.
C) The two sides of a cell membrane face different environments and carry out different functions.
Which of the following structures would decrease the electrochemical gradient across a membrane? A) an aquaporin B) a proton pump C) a potassium channel D) both a proton pump and a sodium channel
C) a potassium channel
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
C) on the inside surface of the vesicle
Which of the following processes includes all of the others? A) osmosis B) facilitated diffusion C) passive transport D) transport of an ion down its electrochemical gradient
C) passive transport
Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer? A) transmembrane proteins B) integral membrane proteins C) peripheral membrane proteins D) cholesterol
C) peripheral membrane proteins
An organism with a cell wall would most likely be unable to take in materials through ________. A) osmosis B) active transport C) phagocytosis D) facilitated diffusion
C) phagocytosis
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 more selectivity D) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot
C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity
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? A) Sodium and glucose compete for the same binding site in the cotransporter. B) Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. D) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
D) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of
Which of the following statements about diffusion is true? A) It is very rapid over long distances. B) It requires an expenditure of energy by the cell. C) It is an active process in which molecules move from a region of lower concentration to a region of higher concentration. D) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
D) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? The animal cell is in ________. A) a hypotonic solution, and the plant cell is in an isotonic solution B) an isotonic solution, and the plant cell is in a hypertonic solution C) a hypertonic solution, and the plant cell is in an isotonic solution D) an isotonic solution, and the plant cell is in a hypotonic solution
D) an isotonic solution, and the plant cell is in a hypotonic solution
Which of the following types of molecules lack hydrophilic domains? A) transmembrane proteins B) integral membrane proteins C) peripheral membrane proteins D) cholesterol
D) cholesterol
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 membrane—more acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of ________. A) passive diffusion B) facilitated diffusion C) active transport D) cotransport
D) cotransport
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? A) antiviral medications that are efficient and work well with most viruses B) intravenous feeding techniques C) medications to slow blood loss D) hydrating drinks with high concentrations of salt and glucose
D) hydrating drinks with high concentrations of salt and glucose
Diffusion of ions across membranes through specific ion channels is driven by ________. A) active transport pumps B) ion concentration gradients only C) electrical gradients only D) ion electrochemical gradients
D) ion electrochemical gradients
According to the fluid mosaic model, a membrane ________. A) is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins B) is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins C) is composed of a mosaic of fluid polysaccharides and amphipathic proteins D) is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins
D) is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins
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? A) the relative hydrophobicity of the drug molecule B) phospholipid composition of lung cell plasma membranes C) specificity of the drug molecule for binding to the extracellular matrix of lung cells D) similarity of the drug molecule to other molecules normally transported lung cells
D) similarity of the drug molecule to other molecules normally transported lung cells
Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane? A) large hydrophobic molecules B) small hydrophobic molecules C) carbon dioxide D) small ions
D) small ions
What type of osmotic environment are elodea cells in?
Hypertonic
How could you tell if a transport mechanism is active?
If the mechanism is using ATP and the molecules are moving from low to high concentration
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.
When a plant cell, such as one from a tulip leaf, is submerged in a hypertonic solution, what is likely to occur?
Plasmolysis will shrink the interior of the cell.
What is the condition of a red blood cell if it has been placed in a hypertonic solution?
Shriveled/crenated
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 swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
Why are lipids and proteins free to move laterally in membranes?
There are only weak hydrophobic interactions in the interior of the membrane.
A plant cell is filling up with water. What is the name of the pressure that is increasing?
Turgor pressure
For a protein to be an integral membrane protein, it would have to be ________.
amphipathic, with at least one hydrophobic region
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic