bio 111 chapters 7-8
22) Which of the following allows water to move much faster across cell membranes? A) the sodium-potassium pump B) ATP C) peripheral proteins D) aquaporins
D) aquaporins
51) 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? 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 salts and glucose
..D) hydrating drinks with high concentrations of salts and glucose
21) 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+
A) CO2
7) Which of the following is a statement of the first law of thermodynamics? A) Energy cannot be created or destroyed. B) The entropy of the universe is decreasing. C) The entropy of the universe is constant. D) Energy cannot be transferred or transformed.
A) Energy cannot be created or destroyed.
20) In solution, why do hydrolysis reactions occur more readily than condensation reactions? A) Hydrolysis increases entropy and is exergonic. B) Hydrolysis raises G, or Gibbs free energy. C) Hydrolysis decreases entropy and is exergonic. D) Hydrolysis increases entropy and is endergonic.
A) Hydrolysis increases entropy and is exergonic.
20) Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A) It exhibits a 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 a specificity for a particular type of molecule.
2) You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose? A) Permeability to glucose will increase. B) Permeability to glucose will decrease. C) Permeability to glucose will stay the same. D) You cannot predict the outcome. You simply have to make the measurement.
A) Permeability to glucose will increase.
50) Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this 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 of life.
17) Which of the following 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 and, therefore, more cholesterol in membranes. 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.
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
26) When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell? A) There is random movement of substances into and out of the cell. B) There is directed movement of substances into and out of the cell. C) There is no movement of substances into and out of the cell. D) All movement of molecules is directed by active transport.
A) There is random movement of substances into and out of the cell.
12) Which of the following types of reactions would decrease the entropy within a cell? A) anabolic reactions B) hydrolysis C) digestion D) catabolic reactions
A) anabolic reactions
3) 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
5) Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? A) catabolism (catabolic pathways) B) metabolism C) anabolism (anabolic pathways) D) dehydration
A) catabolism (catabolic pathways)
4) Which of the following involves a decrease in entropy? A) condensation reactions B) reactions that separate monomers C) depolymerization reactions D) hydrolysis reactions
A) condensation reactions
48) 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
55) 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
17) A chemical reaction that has a positive ΔG is best described as _____. A) endergonic B) enthalpic C) spontaneous D) exergonic
A) endergonic
13) Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellular eukaryotic organisms, _____. A) has occurred in accordance with the laws of thermodynamics B) has caused an increase in the entropy of the planet C) has been made possible by expending Earth's energy resources D) has occurred in accordance with the laws of thermodynamics, by expending Earth's energy resources and causing an increase in the entropy of the planet
A) has occurred in accordance with the laws of thermodynamics
4) The membranes of winter wheat are able to remain fluid when it is extremely cold by _____. A) increasing the percentage of unsaturated phospholipids in the membrane B) increasing the percentage of cholesterol molecules in the membrane C) decreasing the number of hydrophobic proteins in the membrane D) cotransport of glucose and hydrogen
A) increasing the percentage of unsaturated phospholipids in the membrane
51) What is malonic acid's role with respect to succinate dehydrogenase? Malonic acid _____. A) is a competitive inhibitor B) blocks the binding of fumarate C) is a noncompetitive inhibitor D) is an allosteric regulator
A) is a competitive inhibitor
59) Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity? A) localization of enzymes into specific organelles or membranes B) exporting enzymes out of the cell C) connecting enzymes into large aggregates D) hydrophobic interactions
A) localization of enzymes into specific organelles or membranes
58) 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
54) White blood cells engulf bacteria using _____. A) phagocytosis B) pinocytosis C) osmosis D) receptor-mediated exocytosis
A) phagocytosis
35) During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction? A) -40 kcal/mol B) -20 kcal/mol C) 0 kcal/mol D) +20 kcal/mol
B) -20 kcal/mol
16) 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.
56) You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites. One of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. What do these findings tell you about the mechanism of this protein? A) It is probably a structural protein that is involved in cell-to-cell adhesion. B) It is probably an enzyme that works through allosteric regulation. C) It is probably an enzyme that works through competitive inhibition. D) It is probably a cell membrane transport protein-like an ion channel.
B) It is probably an enzyme that works through allosteric regulation.
21) Why is ATP an important molecule in metabolism? A) Its hydrolysis provides an input of free energy for exergonic reactions. B) It provides energy coupling between exergonic and endergonic reactions. C) Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed, releases free energy. D) Its terminal phosphate bond has higher energy than the other two phosphate bonds.
B) It provides energy coupling between exergonic and endergonic reactions.
31) Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst? A) The catalyzed reaction will be slower. B) The catalyzed reaction will have the same ∆G. C) The catalyzed reaction will have higher activation energy. D) The catalyzed reaction will consume all of the catalyst
B) The catalyzed reaction will have the same ∆G.
61) Biological systems use free energy based on empirical data that all organisms require a constant energy input. The first law of thermodynamics states that energy can be neither created nor destroyed. For living organisms, which of the following statements is an important consequence of this first law? A) The energy content of an organism is constant except for when its cells are dividing. B) The organism must ultimately obtain all the necessary energy for life from its environment. C) The entropy of an organism decreases with time as the organism grows in complexity. D) Organisms are unable to transform energy from the different states in which it can exist.
B) The organism must ultimately obtain all the necessary energy for life from its environment.
8) For living organisms, which of the following is an important consequence of the first law of thermodynamics? A) The energy content of an organism is constant. B) The organism ultimately must obtain all of the necessary energy for life from its environment. C) The entropy of an organism decreases with time as the organism grows in complexity. D) Organisms grow by converting energy into organic matter.
B) The organism ultimately must obtain all of the necessary energy for life from its environment.
30) 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 patient's red blood cells will shrivel up because the blood has become hypotonic compared to the cells. B) The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells. C) The patient's red blood cells will shrivel up because the blood has become hypertonic compared to the cells. D) The patient's red blood cells will burst because the blood has become hypertonic compared to the cells.
B) The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.
16) Which of the following is true for all exergonic reactions? A) The products have more total energy than the reactants. B) The reaction proceeds with a net release of free energy. C) The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants. D) A net input of energy from the surroundings is required for the reactions to proceed.
B) The reaction proceeds with a net release of free energy.
60) Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization? A) ATP is more abundant near the plasma membrane. B) They can more readily encounter and phosphorylate other membrane proteins. C) Membrane localization lowers the activation energy of the phosphorylation reaction. D) They flip back and forth across the membrane to access target proteins on either side.
B) They can more readily encounter and phosphorylate other membrane proteins.
46) Which of the following would increase the electrochemical gradient across a membrane? A) a sucrose-proton cotransporter B) a proton pump C) a potassium channel D) both a proton pump and a potassium channel
B) a proton pump
39) In which of the following 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
34) Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's _____. A) entropy B) activation energy C) equilibrium point D) free-energy content
B) activation energy
5) Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At higher temperatures, these regions _____. A) are more fluid than the surrounding membrane B) are less fluid than the surrounding membrane C) detach from the plasma membrane and clog arteries D) have higher rates of lateral diffusion of lipids and proteins into and out of these regions
B) are less fluid than the surrounding membrane
32) The lock-and-key analogy for enzymes applies to the specificity of enzymes _____. A) as they form their tertiary and quaternary structure B) binding to their substrate C) interacting with water D) interacting with ions
B) binding to their substrate
42) How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity? A) by changing the enzyme's stability B) by changing the shape of an enzyme C) by changing the enzyme's pH optimum D) An amino acid change away from the active site cannot alter the enzyme's substrate specificity.
B) by changing the shape of an enzyme
7) 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) attaching the plasma membrane to the cytoskeleton D) establishing a diffusion barrier to charged molecules
B) cell-cell recognition
40) A noncompetitive inhibitor decreases the rate of an enzyme reaction by _____. A) binding at the active site of the enzyme B) changing the shape of the enzyme's active site C) changing the free energy change of the reaction D) acting as a coenzyme for the reaction
B) changing the shape of the enzyme's active site
6) Anabolic pathways _____. A) are usually highly spontaneous chemical reactions B) consume energy to build up polymers from monomers C) release energy as they degrade polymers to monomers D) consume energy to decrease the entropy of the organism and its environment
B) consume energy to build up polymers from monomers
42) 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) ionizes sodium and potassium atoms D) is used to drive the transport of other molecules against a concentration gradient
B) contributes to the membrane potential
19) Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _____ is to _____. A) exergonic; spontaneous B) exergonic; endergonic C) free energy; entropy D) work; energy
B) exergonic; endergonic
36) 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_____. A) and the salt solution are both hypertonic to the cells of the celery stalks B) is hypotonic and the salt solution is hypertonic to the cells of the celery stalks C) is hypertonic and the salt solution is hypotonic to the cells of the celery stalks D) is isotonic and the salt solution is hypertonic to the cells of the celery stalks
B) is hypotonic and the salt solution is hypertonic to the cells of the celery stalks
36) The active site of an enzyme is the region that _____. A) binds allosteric regulators of the enzyme B) is involved in the catalytic reaction of the enzyme C) binds noncompetitive inhibitors of the enzyme D) is inhibited by the presence of a coenzyme or a cofactor
B) is involved in the catalytic reaction of the enzyme
44) The voltage across a membrane is called the _____. A) chemical gradient B) membrane potential C) osmotic potential D) electrochemical gradient
B) membrane potential
41) A sodium-potassium pump _____. A) moves three potassium ions out of a cell and two sodium ions into a cell while producing an ATP for each cycle B) move three sodium ions out of a cell and two potassium ions into a cell while consuming an ATP for each cycle C) moves three potassium ions out of a cell and two sodium ions into a cell while consuming 2 ATP in each cycle D) move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle
B) move three sodium ions out of a cell and two potassium ions into a cell while consuming an ATP for each cycle
43) Which of the following membrane activities requires energy from ATP? 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
18) What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic
B) small and hydrophobic
24) Catabolic pathways _____. A) combine molecules into more energy-rich molecules B) supply energy, primarily in the form of ATP, for the cell's work C) are endergonic D) are spontaneous and do not need enzyme catalysis
B) supply energy, primarily in the form of ATP, for the cell's work
3) Most cells cannot harness heat to perform work because _____. A) heat is not a form of energy B) temperature is usually uniform throughout a cell C) heat can never be used to do work D) heat must remain constant during work
B) temperature is usually uniform throughout a cell
52) The force driving simple diffusion is _____, while the energy source for active transport is _____. A) the concentration gradient; ADP B) the concentration gradient; ATP C) transmembrane pumps; electron transport D) phosphorylated protein carriers; ATP
B) the concentration gradient; ATP
27) A number of systems for pumping ions across membranes are powered by ATP. Such ATP- powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting? A) ATPase activity must be powering an inflow of calcium from the outside of the cell into the SR. B) ATPase activity must be transferring i to the SR to enable this to occur. C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient. D) ATPase activity must be opening a channel for the calcium ions to diffuse back into the SR along the concentration gradient.
C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
9) Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics? A) Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time. B) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe. C) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth. D) Living organisms are able to transform energy into entropy.
C) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
11) Which of the following statements is representative of the second law of thermodynamics? A) Conversion of energy from one form to another is always accompanied by some gain of free energy. B) Without an input of energy, organisms would tend toward decreasing entropy. C) Cells require a constant input of energy to maintain their high level of organization. D) Every energy transformation by a cell decreases the entropy of the universe.
C) Cells require a constant input of energy to maintain their high level of organization.
30) Which of the following is true of enzymes? A) Enzyme function is increased if the 3- D structure or conformation of an enzyme is altered. B) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. C) Enzymes increase the rate of chemical reaction by lowering activation energy barriers. D) Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.
C) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
10) Which of the following statements is a logical consequence of the second law of thermodynamics? A) If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe. B) If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe. C) Every chemical reaction must increase the total entropy of the universe. D) Energy can be transferred or transformed, but it cannot be created or destroyed.
C) Every chemical reaction must increase the total entropy of the universe.
27) Which of the following is true of 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.
26) When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell? A) It is secreted as waste. B) It is used only to regenerate more ATP. C) It may be used to form a phosphorylated intermediate. D) It enters the nucleus and affects gene expression.
C) It may be used to form a phosphorylated intermediate.
1) Which of the following is true of metabolism in its entirety in all organisms? A) Metabolism depends on a constant supply of energy from food. B) Metabolism uses all of an organism's resources. C) Metabolism consists of all the energy transformation reactions in an organism. D) Metabolism manages the increase of entropy in an organism.
C) Metabolism consists of all the energy transformation reactions in an organism.
62) In a biological reaction, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect if malonic acid. Select the correct identification of the molecules described in the reaction. A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate in the reaction. B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate in the reaction. C) Succinate is the substrate, and fumarate is the product in the reaction. D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor in the reaction.
C) Succinate is the substrate, and fumarate is the product in the reaction.
23) You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells? A) hydrophobicity of the drug molecule B) lack of charge on the drug molecule C) similarity of the drug molecule to other molecules transported by the target cells D) lipid composition of the target cells' plasma membrane
C) similarity of the drug molecule to other molecules transported by the target cells
37) What will happen to a red blood cell (RBC), which has an internal ion concentration of about 0.9 percent, if it is placed into a beaker of pure water? A) The cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. B) The cell would shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC. C) The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. D) The cell will remain the same size because the solution outside the cell is isotonic.
C) The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
15) Cell membranes are asymmetrical. 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.
39) Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as _____. A) a noncompetitive inhibitor of the enzyme B) an allosteric activator of the enzyme C) a cofactor necessary for enzyme activity D) a coenzyme derived from a vitamin
C) a cofactor necessary for enzyme activity
58) Which of the following is an example of cooperativity? A) the binding of an end product of a metabolic pathway to the first enzyme that acts in the pathway B) one enzyme in a metabolic pathway passing its product to act as a substrate for the next enzyme in the pathway C) a molecule binding at one unit of a tetramer, allowing faster binding at each of the other three D) binding of an ATP molecule along with one of the substrate molecules in an active site
C) a molecule binding at one unit of a tetramer, allowing faster binding at each of the other three
2) Which of the following is an example of potential rather than kinetic energy? A) water rushing over Niagara Falls B) light flashes emitted by a firefly C) a molecule of glucose D) a crawling beetle foraging for food
C) a molecule of glucose
1) For a protein to be an integral membrane protein, it would have to be _____. A) hydrophilic B) hydrophobic C) amphipathic, with at least one hydrophobic region D) exposed on only one surface of the membrane
C) amphipathic, with at least one hydrophobic region
23) Which of the following is most similar in structure to ATP? A) a pentose sugar B) a DNA nucleotide C) an RNA nucleotide D) an amino acid with three phosphate groups attached
C) an RNA nucleotide
57) Allosteric enzyme regulation is usually associated with _____. A) feedback inhibition B) activating activity C) an enzyme with more than one subunit D) the need for cofactors
C) an enzyme with more than one subunit
38) Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? A) the need for a coenzyme B) allosteric inhibition C) competitive inhibition D) insufficient cofactors
C) competitive inhibition
6) Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes_____. A) are a phospholipid bilayer between two layers of hydrophilic proteins B) are a single layer of phospholipids and proteins C) consist of protein molecules embedded in a fluid bilayer of phospholipids D) consist of a mosaic of polysaccharides and proteins
C) consist of protein molecules embedded in a fluid bilayer of phospholipids
43) For the enzyme- catalyzed reaction shown in the figure, if the initial reactant concentration is 1.0 micromolar, which of these treatments will cause the greatest increase in the rate of the reaction? A) doubling the activation energy needed B) cooling the reaction by 10°C C) doubling the enzyme concentration D) increasing the concentration of reactants to 10.0 micromolar, while reducing the concentration of enzyme by 1/2
C) doubling the enzyme concentration
24) Diffusion _____. A) is very rapid over long distances B) requires an expenditure of energy by the cell C) is a passive process in which molecules move from a region of higher concentration to a region of lower concentration D) requires integral proteins in the cell membrane
C) is a passive process in which molecules move from a region of higher concentration to a region of lower concentration
57) 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
25) Which of the following processes includes all others? A) osmosis B) facilitated diffusion C) passive transport D) transport of an ion down its electrochemical gradient
C) passive transport
8) 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 D) All of these are embedded in the hydrophobic portion of the lipid bilayer.
C) peripheral proteins
53) 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
56) 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.
37) According to the induced fit hypothesis of enzyme catalysis, _____. A) the binding of the substrate depends on the shape of the active site B) some enzymes change their structure when activators bind to the enzyme C) the binding of the substrate changes the shape of the enzyme's active site D) the active site creates a microenvironment ideal for the reaction
C) the binding of the substrate changes the shape of the enzyme's active site
14) The mathematical expression for the change in free energy of a system is ΔG =ΔH - TΔS. Which of the following is (are) correct? A) ΔS is the change in enthalpy, a measure of randomness. B) ΔH is the change in entropy, the energy available to do work. C) ΔG is the change in free energy. D) T is the temperature in degrees Celsius.
C) ΔG is the change in free energy.
49) Which of the following 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 glucose.
33) You have discovered an enzyme that can catalyze two different chemical reactions. Which of the following is most likely to be correct? A) The enzyme contains α-helices and β-pleated sheets. B) The enzyme is subject to competitive inhibition and allosteric regulation. C) Two types of allosteric regulation occur: The binding of one molecule activates the enzyme, while the binding of a different molecule inhibits it. D) Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.
D) Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.
25) When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated? A) It is used to power yet more cellular work. B) It is used to store energy as more ATP. C) It is used to generate ADP from nucleotide precursors. D) It is lost to the environment.
D) It is lost to the environment.
19) Which of the following most accurately describes selective permeability? A) An input of energy is required for transport. B) Lipid-soluble molecules pass through a membrane. C) There must be a concentration gradient for molecules to pass through a membrane. D) Only certain molecules can cross a cell membrane.
D) Only certain molecules can cross a cell membrane.
22) When 10,000 molecules of ATP are hydrolyzed to ADP and i in a test tube, about half as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation? A) Cells are open systems, but a test tube is an isolated system. B) Cells are less efficient at heat production than nonliving systems. C) The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube does not need enzymes. D) Reactant and product concentrations in the test tube are different from those in the cell.
D) Reactant and product concentrations in the test tube are different from those in the cell.
40) When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution, what is likely to occur? A) The cell will burst. B) Plasmolysis will shrink the interior. C) The cell will become flaccid. D) The cell will become turgid.
D) The cell will become turgid.
9) Why are lipids and proteins free to move laterally in membranes? A) The interior of the membrane is filled with liquid water. B) Lipids and proteins repulse each other 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.
D) There are only weak hydrophobic interactions in the interior of the membrane.
18) Chemical equilibrium is relatively rare in living cells. An example of a reaction at chemical equilibrium in a cell would be _____. A) one in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium B) one in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings C) an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment D) a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell
D) a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell
38) 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
15) A system at chemical equilibrium _____. A) consumes energy at a steady rate B) releases energy at a steady rate C) has zero kinetic energy D) can do no work
D) can do no work
52) HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon? A) vaccination B) denaturation C) allosteric regulation D) competitive inhibition
D) competitive inhibition
47) 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. Phosphate transport is an example of _____. A) passive diffusion B) facilitated diffusion C) active transport D) cotransport
D) cotransport
45) Ions diffuse across membranes through specific ion channels down _____. A) their chemical gradients B) their concentration gradients C) the electrical gradients D) their electrochemical gradients
D) their electrochemical gradients
