Principles of Life 2nd Edition by David M. Hillis – Test Bank


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Sample Questions Posted Below





1. Biological membranes are composed primarily of
  A) nucleotides and nucleosides.
  B) enzymes, electron acceptors, and electron donors.
  C) fatty acids.
  D) monosaccharides.
  E) lipids.



2. The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are
  A) integral membrane proteins.
  B) carbohydrates.
  C) lipids.
  D) nucleic acids.
  E) peripheral membrane proteins.



3. In biological membranes, the phospholipids are arranged in a _______, with the _______.
  A) bilayer; fatty acids pointing toward each other
  B) bilayer; fatty acids facing outward
  C) single layer; fatty acids facing the interior of the cell
  D) single layer; phosphorus-containing region facing the interior of the cell
  E) bilayer; phosphorus groups in the interior of the membrane



4. A characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis is the
  A) ratio of one protein molecule for every 25 phospholipid molecules.
  B) capacity of lipids to associate and maintain a bilayer organization.
  C) constant length of the fatty acid chain and the degree of saturation.
  D) ability of phospholipid molecules to flip over and trade places with other phospholipid molecules.
  E) asymmetrical distribution of membrane transport proteins.



5. Which statement about cholesterol molecules is true?
  A) They help hold a membrane together.
  B) They alter the fluidity of the membrane.
  C) They attach to carbohydrates.
  D) They disrupt membrane function.
  E) They transport ions across membranes.



6. Houseplants adapted to indoor temperatures may die if they are left outdoors, because in a cold environment their
  A) DNA cannot function.
  B) membranes lack adequate fluidity.
  C) photosynthesis is impaired.
  D) membranes contain too many unsaturated fatty acids.
  E) membranes need more cholesterol.



7. Contact with ice numbs a person’s fingers because at lower temperatures
  A) membrane fluidity is reduced in nerve cells.
  B) no ATP can be produced in the fingers.
  C) protein kinases are activated in the nerves.
  D) membranes in nerve cells unzip.
  E) there are changes in the lipid composition of the membranes in nerve cells.



8. In hibernating animals during the winter,
  A) signal transduction pathways cease.
  B) membrane lipid composition changes: saturated fatty acids are replaced with unsaturated fatty acids.
  C) membranes toughen as more saturated fatty acids accumulate in them.
  D) there are no changes in lipid composition.
  E) integral proteins shrink as temperatures fall.



9. The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by
  A) synthesizing new forms of cholesterol.
  B) closing protein channels.
  C) decreasing the number of hydrophobic proteins present.
  D) replacing saturated fatty acids with unsaturated fatty acids.
  E) using fatty acids with longer tails.



10. Which type of membrane protein would likely be most easily removed in a laboratory experiment?
  A) Integral membrane proteins
  B) Channel proteins
  C) Peripheral membrane proteins
  D) Transmembrane proteins
  E) Gated channels



11. A protein that forms an ion channel through a membrane is most likely
  A) a peripheral membrane protein.
  B) a transmembrane protein.
  C) a phospholipid.
  D) an enzyme.
  E) entirely outside the phospholipid bilayer.



12. The LDL receptor is an integral membrane protein that crosses the plasma membrane, with portions of the protein extending both outside and into the interior of the cell. The amino acid side chains (R groups) in the region of the protein that crosses the membrane are most likely
  A) charged.
  B) hydrophilic.
  C) hydrophobic.
  D) carbohydrates.
  E) lipids.



13. The hydrophilic regions of a membrane protein are most likely
  A) present only in muscle cells.
  B) associated with the fatty acid region of the lipids.
  C) in the interior of the membrane.
  D) exposed on the surface of the membrane.
  E) either on the surface or inserted into the interior of the membrane.



14. Which statement about peripheral membrane proteins is true?
  A) They have hydrophobic regions within the lipid portion of the bilayer.
  B) They have hydrophilic regions that protrude in aqueous environments on both sides of the membrane.
  C) They frequently flip from one side of the bilayer to the other.
  D) They control the rate of simple diffusion.
  E) Their polar regions interact with complementary regions of integral membrane proteins.



15. The two sides of a membrane can be split apart from each other by an experimental technique known as freeze-fracturing. When one side of a freeze-fractured membrane is examined under the electron microscope, the exposed interior of the membrane bilayer appears to be covered with bumps. These bumps are most likely
  A) integral membrane proteins.
  B) ice crystals.
  C) glycolipids.
  D) organelles.
  E) vesicles.



16. When a mouse cell and a human cell are fused, the membrane proteins of the two cells become uniformly distributed over the surface of the hybrid cell. This occurs because
  A) many proteins can move around within the bilayer.
  B) all proteins are anchored within the membrane.
  C) proteins are asymmetrically distributed within the membrane.
  D) all proteins in the plasma membrane are peripheral.
  E) different membranes contain different proteins.



17. Plasma membranes are relatively impermeable to water-soluble molecules because
  A) the membranes are waxy.
  B) water molecules are nonpolar.
  C) their bilayer is comprised of phospholipids.
  D) they have salt crystals embedded within them.
  E) large proteins extend through both sides of the membranes.



18. How do the cell membranes of a hibernating animal change in colder temperatures?
  A) They release all of their peripheral membrane proteins.
  B) Saturated fatty acids are more tightly packed.
  C) Integral membrane proteins increase in number.
  D) Unsaturated fatty acids make up more of the lipid composition.
  E) Fatty acids with longer tails increase in number.



19. Which of the following functions as a recognition site for interactions between cells?
  A) RNA
  B) Phospholipid
  C) Cholesterol
  D) Fatty acid
  E) Glycolipid



20. The rate at which a substance diffuses is not affected by the
  A) diameter of the molecules or ions.
  B) temperature of the solution.
  C) color of the substance.
  D) concentration gradient in the system.
  E) Both a and b



21. The existence of a concentration gradient of glucose across a membrane means that
  A) there is a high concentration of glucose on both sides of the membrane.
  B) the glucose molecules are more crowded on one side of the membrane than on the other.
  C) there is a high concentration of water on both sides of the membrane.
  D) the glucose molecules are chemically bonded more tightly on one side of the membrane than on the other.
  E) there are more glucose molecules within the bilayer of the membrane than outside of the membrane.



22. Which statement about diffusion is false?
  A) Diffusion does not require ATP.
  B) Diffusion continues until the molecular concentrations are in equilibrium.
  C) In diffusion, molecules move from areas of greater concentration to areas of lesser concentration.
  D) Diffusion is a random process.
  E) Simple diffusion depends upon specific carrier proteins.



23. If a drop of red ink is placed in one end of a shallow pan filled with water, and a drop of green ink is placed in the other end, which of the following will be true at equilibrium?
  A) The red ink will be uniformly distributed in one half of the pan, and the green ink will be uniformly distributed in the other half of the pan.
  B) The red and green inks will be uniformly distributed throughout the pan.
  C) Each ink will begin moving down its concentration gradient.
  D) The concentration of each ink will be higher at one end of the pan than at the other end.
  E) No predictions can be made without knowing the molecular weights of the pigment molecules.



24. If a hospital patient is mistakenly given an IV of pure water instead of a saline solution that is isotonic to blood, the patient’s red blood cells will
  A) shrink and collapse.
  B) release water to the plasma along its concentration gradient.
  C) absorb water from the plasma and eventually burst.
  D) transport equal amounts of water across the cell membrane in both directions.
  E) work with white blood cells to maintain the water level in the plasma.



25. The difference between osmosis and diffusion is that
  A) diffusion is passive transport, whereas osmosis is active transport.
  B) only in diffusion do molecules move from areas of high concentration to areas of low concentration.
  C) only diffusion refers to the movement of materials across a semipermeable membrane.
  D) osmosis refers specifically to the movement of water, whereas diffusion refers to the movement of any type of molecules.
  E) only the process of osmosis varies according to the kinds of particles present.



26. The process of osmosis allows water molecules to pass through specialized channels in membranes. Which statement about osmosis is true?
  A) Water will move across a membrane to a region with less solute.
  B) Water will move across a membrane to a region with more solute.
  C) The direction of osmosis is temperature dependent.
  D) If the membrane does not allow solutes to pass, water will be equal on both sides.
  E) A higher solute concentration on one side of a membrane indicates a higher water concentration on that side.



27. Osmosis is a specific form of
  A) diffusion.
  B) pinocytosis.
  C) active transport.
  D) secondary active transport.
  E) movement of water by carrier proteins.



28. Which of the following is not one of the functional roles of membrane proteins?
  A) Allowing movement of molecules that otherwise would be excluded by the lipid components of the membrane
  B) Transferring signals from outside the cell to inside the cell
  C) Facilitating the movement of water across the membrane
  D) Facilitating the transport of macromolecules across the membrane
  E) Stabilizing the lipid bilayer



29. Which of the following is an example of passive transport?
  A) Facilitated diffusion
  B) The sodium–potassium pump
  C) Phagocytosis
  D) Exocytosis
  E) Pinocytosis



30. You are doing a summer internship in a cell biology lab. Your supervisor asks you to change the medium on some cells she is growing. You do so and then examine the cells under a microscope. To your dismay, you can’t find any cells and see only what looks like cell debris. What most likely happened to your cells and why?
  A) The cells shrank because the new medium was hypotonic to the cells.
  B) The cells shrank because the new medium was hypertonic to the cells.
  C) The cells burst because the new medium was hypertonic to the cells.
  D) The cells burst because the new medium was hypotonic to the cells.
  E) The cells burst, although the new medium could not have been the cause.



31. If aquaporins are injected into the membranes of epithelial cells that line blood vessels,
  A) the flow of Na+ through aquaporins will increase.
  B) the intracellular concentration of K+ will increase.
  C) carrier proteins will bind glucose and enter the bloodstream.
  D) the membranes will become more permeable to water.
  E) the electrical properties of the cells will be altered.



32. Osmosis moves water from a region of _______ to a region of _______.
  A) high concentration of dissolved material; low concentration of dissolved material
  B) low concentration of dissolved material; high concentration of dissolved material
  C) hypertonic solution; hypotonic solution
  D) hypertonic solution; isotonic solution
  E) low concentration of water; high concentration of water



33. When placed in water, wilted plants lose their limpness because of
  A) active transport of salts from the water into the plant cells.
  B) active transport of salts into the water from the plant cells.
  C) osmosis of water into the plant cells.
  D) osmosis of water from the plant cells.
  E) diffusion of water from the plant cells.



34. When a severely dehydrated patient is brought to the hospital, an IV of normal saline is started immediately. Distilled water is not used because
  A) it would cause water to leave the cells of the patient and the cells would collapse.
  B) nutrients are provided by the saline.
  C) it would cause the patient’s blood cells to swell and eventually burst.
  D) normal saline is more economical.
  E) the distilled water might be contaminated by bacteria.



35. If a red blood cell is placed in an isotonic solution, it will
  A) shrivel.
  B) swell and burst.
  C) shrivel and then return to normal.
  D) swell and then return to normal.
  E) take up and release water at equal rates.



36. When placed in a hypertonic solution, animal cells
  A) shrink.
  B) swell.
  C) burst.
  D) transport water out using ATP.
  E) transport water in using ATP.



37. Which of the following is the driving force for simple diffusion?
  A) Concentration gradient
  B) ATP hydrolysis
  C) ADP hydrolysis
  D) Phosphorylation
  E) GTP–GDP exchange



38. Which of the following is the driving force for facilitated diffusion?
  A) Concentration gradient
  B) ATP hydrolysis
  C) ADP hydrolysis
  D) Phosphorylation
  E) GTP–GDP exchange



39. Osmosis
  A) helps plant cells maintain turgor pressure.
  B) moves macromolecules from one cell to another.
  C) facilitates the “flipping” of proteins from one side of the membrane to the other.
  D) keeps concentrations uniform in all cells.
  E) causes cells to lose water when they are placed in a hypotonic solution.



40. In a hypothetical study, cells are placed in a solution of glucose in which the concentration of glucose is gradually increased. At first, the rate at which glucose enters the cells is found to increase as the concentration of the glucose solution is increased. But when the glucose concentration of the solution is increased above 10 M, the rate no longer increases. Which of the following is the likely mechanism for glucose transport into these cells?
  A) Facilitated diffusion via a carrier protein
  B) Facilitated diffusion via a channel protein
  C) Pinocytosis
  D) Tertiary active transport
  E) Hydrolysis



41. What is the membrane property that helps ensure the diffusion of glucose into a cell that has a high energy need?
  A) A glucose pump
  B) Specific carrier proteins found only in large muscle cells
  C) A high number of carrier proteins specific for glucose
  D) Special sensitivity to an extracellular environment high in glucose
  E) Additional pores through which water can flow, carrying dissolved glucose



42. Which transport system can move an ion across the plasma membrane against its concentration gradient without using ATP?
  A) Secondary active transport
  B) Primary active transport
  C) Simple diffusion
  D) Facilitated diffusion
  E) Facilitated diffusion via a carrier protein



43. If you were designing a drug with an intracellular target, which type of transport system would you want to include in your design as the most efficient way to deliver the drug?
  A) Secondary active transport
  B) Primary active transport
  C) Simple diffusion
  D) Facilitated diffusion
  E) Facilitated diffusion via a carrier protein



44. Active transport usually moves molecules
  A) in the same direction as diffusion moves them.
  B) in a direction opposite to the one in which diffusion moves them.
  C) in a direction that tends to bring about equilibrium.
  D) from a solution with a lower pH toward one with a higher pH.
  E) from inside to outside the cell.



45. Plant cells transport sucrose across the vacuole membrane against its concentration gradient by a process known as
  A) simple diffusion.
  B) active transport.
  C) passive transport.
  D) facilitated diffusion.
  E) cellular respiration.



46. Which of the following is not involved in secondary active transport?
  A) The direct use of ATP
  B) Coupling to another transport system
  C) Use of an existing concentration gradient
  D) The plasma membrane
  E) The ability to concentrate the transported molecule



47. Which of the following is the driving force for active transport?
  A) Concentration gradient
  B) ATP hydrolysis
  C) ADP hydrolysis
  D) Phosphorylation
  E) GTP–GDP exchange



48. One reason cancer therapy often fails is that the targeted cells become resistant to the drugs that are supposed to kill them. Which of the following is the most likely mechanism of this resistance?
  A) Carrier proteins block diffusion of the drugs into the cancer cells.
  B) Membrane proteins pump nutrients into the cancer cells.
  C) Drugs diffuse into the cancer cells via simple diffusion.
  D) Membrane proteins actively transport the drugs out of the cancer cells.
  E) Channel proteins pump ions into the cancer cells.



49. For each molecule of ATP consumed during active transport of sodium and potassium, there is an import of _______ ion(s) and an export of _______ ion(s).
  A) two Na+; three K+
  B) two Na+; one K+
  C) one K+; three Na+
  D) two K+; three Na+
  E) three K+; two Na+



50. In the intestine, Na+ and an amino acid bind to the same transport protein that moves the two substances in the same direction. This is an example of
  A) passive transport.
  B) simple diffusion.
  C) secondary active transport.
  D) facilitated diffusion.
  E) simple secondary diffusion.



51. Amino acids enter cells against their concentration gradients by means of
  A) simple diffusion.
  B) facilitated diffusion.
  C) primary active transport.
  D) secondary active transport.
  E) osmosis.



52. If a cell needs to acquire dissolved solutes continuously, which mechanism will most likely aid this process?
  A) Osmosis
  B) Diffusion
  C) Receptor-mediated endocytosis
  D) Phagocytosis
  E) Pinocytosis



53. A selectively permeable membrane ensures that
  A) a cell can maintain its ion concentrations by diffusion.
  B) macromolecules can be obtained through active transport.
  C) dissolved substances can be taken up by pinocytosis.
  D) essential macromolecules and other polar molecules cannot leave the cell by diffusion.
  E) fluids can be obtained rapidly.



54. Which statement does not correctly describe the processes by which materials are taken up by the cell?
  A) Vesicles touch the cell membrane and release their contents through a pore.
  B) The plasma membrane forms small vesicles around fluids and dissolved substances.
  C) Bacteria are engulfed by the plasma membranes of white blood cells.
  D) Specific molecules are transported through receptor-mediated endocytosis.
  E) Phagosomes formed by the plasma membrane fuse with lysosomes.



55. Phagocytosis refers to
  A) the specific import of small molecules.
  B) invagination of the plasma membrane.
  C) the export of macromolecules.
  D) the delivery of receptor proteins to specific locations within the cell.
  E) the nonspecific intake of fluids by the cell.



56. Receptor-mediated endocytosis is the primary mechanism for import of
  A) clathrin.
  B) all macromolecules.
  C) ions.
  D) cholesterol.
  E) integral membrane proteins.



57. Which process does not involve the uptake of materials into the cell?
  A) Exocytosis
  B) Pinocytosis
  C) Endocytosis
  D) Receptor-mediated endocytosis
  E) Phagocytosis



58. To respond to a signal, a cell must have a(n) _______ molecule that can detect the signal.
  A) paracrine
  B) receptor
  C) autocrine
  D) responder
  E) All of the above



59. Chemical signals reaching a cell deep inside a multicellular organism may come from
  A) the brain.
  B) the lymphatic system.
  C) glands.
  D) other cell types.
  E) All of the above



60. In a signal transduction pathway, the signal activates a(n)
  A) paracrine molecule.
  B) responder.
  C) receptor.
  D) hormone.
  E) effector molecule.



61. The signals that bind to receptors of the same cell that made them are known as
  A) paracrine signals.
  B) parasitic signals.
  C) autocrine signals.
  D) hormones.
  E) responders.



62. The signals that bind to receptors on nearby cells are known as
  A) paracrine signals.
  B) parasitic signals.
  C) autocrine signals.
  D) hormones.
  E) responders.



63. Signals that travel to distant cells through the circulatory system are known as
  A) paracrine signals.
  B) parasitic signals.
  C) autocrine signals.
  D) hormones.
  E) responders.



64. Vitamin A is a relatively small, lipid-soluble molecule that can behave as a hormone. Most likely its receptor
  A) is an ion channel receptor.
  B) is a protein kinase receptor.
  C) involves a G protein.
  D) is not connected to the cell membrane.
  E) highly vulnerable to antagonists.



65. A molecule that binds to the particular three-dimensional structure of another molecule’s receptor site is known as a(n)
  A) responder.
  B) receptor.
  C) ligand.
  D) ion channel.
  E) filament.



66. In general, all cell signaling causes
  A) increased expression of genes.
  B) an influx of ions.
  C) protein kinase activity.
  D) G protein activation.
  E) a change in receptor conformation.



67. Which statement about ligands and receptors is true?
  A) For most ligand–receptor complexes, binding is favored.
  B) Ligand–receptor interactions are reversible.
  C) Many drugs that alter human behavior prevent the binding of receptors’ specific ligands.
  D) Ligand–receptor interactions often induce conformational changes in channels.
  E) All of the above



68. In what way do ligand–receptor interactions differ from enzyme–substrate reactions?
  A) The ligand signal is not usually metabolized into useful products.
  B) Receptor–ligand interactions do not obey the laws of mass action.
  C) Inhibitors never bind to the ligand-binding site.
  D) Reversibility never occurs in ligand–receptor interactions.
  E) Enzyme–substrate reactions and the ligand–receptor interactions do not differ.



69. Signal ligands can be divided into two groups according to the location of their receptors. Which of the following are the two classes of receptors?
  A) Plasma membrane and ion channel
  B) Plasma membrane and protein kinase
  C) Ion channel and cytoplasmic
  D) G protein–linked and protein kinase
  E) Membrane and intracellular



70. Which molecule has a protein kinase receptor?
  A) Insulin
  B) Estrogen
  C) Acetylcholine
  D) Sodium
  E) G protein



71. Which of the following bind(s) to the acetylcholine receptor?
  A) Estrogen
  B) Acetylcholine
  C) Sodium
  D) Insulin
  E) Protein kinases



72. Which statement about the insulin receptor is false?
  A) It is not an ion channel.
  B) It is a protein kinase receptor.
  C) It catalyzes the phosphorylation of insulin-response substrates.
  D) It is located entirely within the cytoplasm.
  E) It is not regulated by phosphorylation.



73. Which molecule has an ion channel receptor?
  A) Insulin
  B) Estrogen
  C) Acetylcholine
  D) Epinephrine
  E) Norepinephrine



74. Which statement about acetylcholine is true?
  A) It binds to a sodium channel receptor.
  B) It acts as a neurotransmitter.
  C) When bound to its receptor, it allows sodium to diffuse down its concentration gradient.
  D) It binds to receptors on skeletal muscle cells.
  E) All of the above



75. Which statement is false?
  A) Cells are bombarded with numerous signals, but they respond to only a few.
  B) A cell’s receptors determine whether or not the cell will respond to a signal.
  C) Receptor proteins are very specific.
  D) Protein kinase receptors are a type of cytoplasmic receptor.
  E) All of the above are true; none is false.



76. After the GTP-bound subunit of the G protein separates from the rest of the G protein, it travels until it encounters
  A) an activator.
  B) a receptor.
  C) an effector protein.
  D) a protein kinase.
  E) another G protein.



77. For a G protein to play its part in moving events forward in a signal pathway,
  A) GDP must be released, and a GTP must occupy the nucleotide-binding site.
  B) GTP must be released, and a GDP must occupy the nucleotide-binding site.
  C) cGMP must occupy the otherwise empty nucleotide-binding site.
  D) cGMP must leave the otherwise occupied nucleotide-binding site.
  E) it must be linked to a specific intracellular receptor.



78. Which statement about G proteins is true?
  A) G proteins contain only one important binding site.
  B) When a G protein binds to an activated receptor protein, ADP is exchanged for ATP.
  C) G protein–linked receptors are transmembrane proteins.
  D) G proteins usually float free in the cytoplasm.
  E) G proteins signal only the cell from which they are secreted.



79. If a G protein were unable to release its bound nucleotide but could hydrolyze it, signal transduction would
  A) cease.
  B) be continuous.
  C) be unaffected.
  D) be constantly switching on and off.
  E) be unpredictable.



80. G proteins do not bind to
  A) GTP.
  B) GDP.
  C) their receptor.
  D) effector proteins.
  E) glucose.



81. Which molecule acts as a second messenger in the cascade by which epinephrine stimulates the activation of the enzyme glycogen phosphorylase?
  A) Adenosine
  B) Caffeine
  C) Citric acid
  D) Cyclic AMP
  E) Adenylyl cyclase



82. Which of the following would likely not be observed in a person injected with epinephrine?
  A) Decreased production of cAMP in liver cells
  B) Inactivation of glycogen synthase
  C) Increased glucose mobilization
  D) Activation of G proteins
  E) All of the above would be observed.



83. A benefit of the many steps involved in a protein kinase cascade is that they allow for
  A) activation or inhibition of many enzymes.
  B) amplification of the signal.
  C) distribution of the signal throughout the inside of the cell.
  D) variation in the response.
  E) All of the above



84. Which of the following represents the correct ordering of the number of molecules that are activated by a single molecule of epinephrine, from highest to lowest?
  A) cAMP, phosphorylase kinase, glycogen phosphorylase
  B) Glycogen phosphorylase, phosphorylase kinase, cAMP
  C) cAMP, glycogen phosphorylase, phosphorylase kinase
  D) Glycogen phosphorylase, cAMP, phosphorylase kinase
  E) Phosphorylase kinase, glycogen phosphorylase, cAMP



85. How does a protein kinase cascade amplify an intercellular signal?
  A) Protein kinase molecules open cell junctions, amplifying the intercellular signal.
  B) The activated G protein binds and activates a second protein, amplifying the signal.
  C) Nitric oxide opens cell channels, which allows protein kinase molecules to move quickly from cell to cell.
  D) Second messengers create shortcuts that create multiple cascades.
  E) Sequential activation of protein kinases can lead to the activation of thousands of effector proteins.



86. Which statement about cyclic AMP is false?
  A) It is formed from ATP.
  B) In some circumstances it can bind to a protein kinase in the cytoplasm.
  C) The enzyme adenylyl cyclase catalyzes its formation from ATP.
  D) It is a second messenger.
  E) It has enzymatic activity.



87. Which enzyme converts cAMP back to AMP?
  A) Phosphodiesterase
  B) Protein kinase
  C) Adenylyl cyclase
  D) Protein phosphatase
  E) ATPase



88. Increased synthesis of phosphodiesterase would lead to
  A) decreased concentration of cyclic AMP.
  B) increased concentration of cyclic AMP.
  C) increased concentration of epinephrine.
  D) decreased concentration of G proteins.
  E) inhibition of adenylyl cyclase.



89. Many signal transduction pathways cause
  A) alterations in gene expression.
  B) upregulation of genes.
  C) the switching off of genes.
  D) an alteration of the abundance of enzymes.
  E) All of the above



90. The molecular structure of caffeine mimics the molecular structure of
  A) paracrine.
  B) aspirin.
  C) adenosine.
  D) autocrine.
  E) phosphorine.



91. Adenosine is the normal _______ for its membrane receptor.
  A) antagonist
  B) enzyme
  C) ligand
  D) fatty acid
  E) carbohydrate moiety



92. Most of the lipids that make up biological membranes are called _______.



93. Biological membranes are composed of a continuous phospholipid bilayer in which proteins are embedded. This general design is known as the _______ model.



94. Membrane proteins covalently bonded to carbohydrates are called _______.



95. Integral membrane proteins that extend all the way through the bilayer and have both ends exposed are called _______ proteins.



96. The process of random movement of molecules toward a state of equilibrium is called _______.



97. A solution in which the solute molecules are uniformly distributed is said to be at _______.



98. The effectiveness of many anesthetics in reducing feeling or sensation is directly related to their _______ in membrane _______.



99. The ability of membranes to allow some substances to pass through, but not others, is called _______.



100. Plants and some animal cells (such as red blood and kidney cells) have membrane channels that allow water to pass through. These channels are called _______.



101. Primary active transport involves the direct hydrolysis of _______.



102. Secondary active transport does not use _______ directly.



103. The glucose transporter is a _______ protein that allows glucose to enter the cell at a faster rate than would be possible by simple diffusion.



104. The process of _______ involves coated pits, clathrin, and coated vesicles.



105. The process by which the plasma membrane engulfs large particles or even whole cells is called _______.



106. Typically, a signal transduction pathway involves a signal, a _______, and a response.



107. Receptors bind to their ligands noncovalently according to chemistry’s law of _______.



108. The mammalian hormone insulin binds to a _______ receptor on the outside surface of the cell and initiates a response.



109. Phosphorylation changes the _______ of a protein and thus its _______.



110. An important consequence of the multiple steps that make up a signal transduction cascade is that the signal becomes _______.



111. Caffeine restores wakefulness because it binds to receptors for _______, thus preventing this chemical from causing drowsiness.



Use the following to answer questions 112-113:


Refer to the diagram below showing the fluid mosaic model.




112. What does the green dot structure labeled “C” represent, to what type of molecule is it attached, and to what general group does this molecule belong?



113. Which of the labeled components affects the fluidity of the fatty acids in the membrane, and why?



Use the following to answer questions 114-115:


Refer to the diagram below showing a phospholipid bilayer.




114. Describe the portions of the phospholipid bilayer shown with the orange and blue backgrounds.



115. Describe the portion of the phospholipid bilayer with the white background.



Use the following to answer questions 116-117:


The graph below shows the relationship between glucose concentration outside a cell and the rate of glucose diffusion across a cell membrane that has carrier proteins to facilitate diffusion.




116. Explain why the graph reaches a plateau.



117. How would this graph change as the concentration of glucose outside the cell becomes less than inside?



118. The images below show three different solute concentrations of two solutions separated by a membrane, along with the resulting direction of osmosis. Identify the type of solution found outside the cell in each image.




119. The images below represent what happens to a red blood cell placed in three different types of solutions. Describe each type of solution and the resulting flow of water molecules.




Use the following to answer questions 120-121:


In the series of photos below, the plant cells in the middle (panel B) are in an isotonic environment. In panel A and C, the arrow indicates the direction of water movement.




120. What likely happened to make the cells appear as they do in photo A?



121. What likely happened to make the cells appear as they do in photo C?



122. If a cell is bathed in an extracellular solution high in Na+, what type of ion movement would maintain the proper balance of Na+ ions between the inside and the outside of the cell?



123. If hydrolysis of ATP is temporarily blocked, such that transport processes requiring an energy source are halted, what will most likely happen to the ionic concentrations of Na+ and K+ inside the cell?



124. If a cell requires a particular amino acid that exists in low extracellular concentration, which method of uptake would be most efficient when the amino acid is present outside the cell?



125. In terms of specificity, describe the difference between phagocytosis and receptor-mediated endocytosis.



126. Draw what would happen when a hormone binds to a receptor, as shown in the diagram below.





Answer Key


1. E
2. C
3. A
4. B
5. B
6. B
7. A
8. B
9. D
10. C
11. B
12. C
13. D
14. E
15. A
16. A
17. C
18. D
19. E
20. C
21. B
22. E
23. B
24. C
25. D
26. B
27. A
28. E
29. A
30. D
31. D
32. B
33. C
34. C
35. E
36. A
37. A
38. A
39. A
40. A
41. C
42. A
43. B
44. B
45. B
46. A
47. B
48. D
49. D
50. C
51. D
52. E
53. D
54. A
55. B
56. D
57. A
58. B
59. E
60. C
61. C
62. A
63. D
64. D
65. C
66. E
67. E
68. A
69. E
70. A
71. B
72. D
73. C
74. E
75. D
76. C
77. A
78. C
79. A
80. E
81. D
82. A
83. E
84. B
85. E
86. E
87. A
88. A
89. E
90. C
91. C
92. phospholipids
93. fluid mosaic
94. glycoproteins
95. transmembrane
96. diffusion
97. equilibrium
98A. solubility
98B. lipids
99. selective permeability
100. aquaporins
101. ATP
102. ATP
103. carrier
104. receptor-mediated endocytosis
105. phagocytosis
106. receptor
107. mass action
108. protein kinase
109A. shape
109B. function
110. amplified
111. adenosine
112. It is a carbohydrate attached to a transmembrane protein. Collectively, this is called a glycoprotein.
113. D (cholesterol), because it intercalates between the fatty acid tails of phospholipids and influences membrane fluidity.
114. The orange and blue areas contain the charged, or polar, hydrophilic portions (or “heads”) of phospholipids which interact with water molecules.
115. The white area contains the nonpolar hydrophobic fatty acids (or “tails”) of phospholipids.
116. Once the carrier proteins are all occupied, or saturated, the rate of facilitated diffusion is maximal.
117. The rate of diffusion would decrease until there was no net influx of glucose.
118. (A) Hypertonic on the outside; (B) hypotonic on the outside; (C) isotonic
119. (A) Hypotonic solution, water enters the cell; (B) isotonic solution, no net movement of water; (C) hypertonic solution, water flows out of cell
120. Water has flowed out of the cell into the environment, which is now hypertonic to the cell. The cell membranes have shrunken away from the cell wall.
121. Water has flowed into the cells. The cell membranes have expanded toward the cell wall. This indicates that the environment has become hypotonic to the cell.
122. Active transport against the concentration gradient of Na+
123. Diffusion will progress toward equilibrium, with sodium leaking into the cell and potassium leaving the cell.
124. Secondary active transport
125. Receptor-mediated endocytosis is more specific in terms of what it brings into the cell because it only brings in materials associated with specific receptors. Phagocytosis responds to a ligand; however, since it engulfs a large amount of material it is not specific with regard to the materials within the particle or cell that is engulfed.





1. If you were atop Mt. Everest, where 21 percent of the molecules in the air are O2 and the partial pressure of oxygen is one-third that at sea level, approximately how many cubic meters of air would you need to breathe to gain the same number of oxygen molecules that you would gain from one cubic meter of air at sea level?
  A) 1
  B) 3
  C) 5
  D) 6
  E) 9



2. Humans have difficulty obtaining enough oxygen while breathing at high elevations because _______ at low elevations.
  A) CO2 makes up a higher percentage of the air than it does
  B) the temperature is lower than it is
  C) the barometric pressure is higher than it is
  D) the air is drier than it is
  E) the partial pressure of O2 is lower than it is



3. Gas exchange in animals always involves
  A) lungs.
  B) breathing movements.
  C) neural control.
  D) diffusion between internal body fluids and the outside medium.
  E) active transport of gases.



4. The respiratory gases of animals are
  A) carbon dioxide and water vapor.
  B) oxygen and nitrogen.
  C) nitrogen and carbon dioxide.
  D) oxygen and carbon dioxide.
  E) oxygen and water vapor.



5. Breathing provides the body with the oxygen required to support the energy metabolism of all cells and also eliminates _______, one of the waste products of cell metabolism.
  A) carbon dioxide
  B) carbon monoxide
  C) carbon tetrachloride
  D) calcium carbonate
  E) carbonic acid



6. Oxygen is exchanged between the body fluids of an animal and its environment by
  A) osmosis.
  B) active transport.
  C) diffusion.
  D) facilitated transport.
  E) pinocytosis.



7. All animals undergoing cellular respiration must get rid of CO2 because
  A) as CO2 increases, it interferes with lung function.
  B) as CO2 increases, it makes body fluids more acidic.
  C) as CO2 increases, it decreases brain function.
  D) as CO2 increases, it is less able to be stored as sugar.
  E) CO2 is incredibly toxic.



8. In your own body, which pathway is an example of the longest path an O2 molecule must take to arrive at its destination?
  A) From the nose to the lungs
  B) From the alveoli to the capillaries in the lungs
  C) From the capillary blood of the lungs to an erythrocyte
  D) From the lungs to a calf muscle
  E) From the tissue capillaries to a muscle cell



9. At sea level, O2 makes up about _______ percent of the gas molecules in the air.
  A) 1
  B) 15
  C) 21
  D) 70
  E) 100



10. According to Fick’s law, which event would cause a decrease in the rate of diffusion?
  A) A decrease in the size of the respiratory membrane (A)
  B) A decrease in the distance (L) between the two surfaces
  C) An increase in the partial pressure difference of the gas at its two locations (P1P2)
  D) An increase in the size of the respiratory membrane (A)
  E) None of the above



11. If the partial pressure of oxygen in the blood is higher than the partial pressure of oxygen in the body’s tissues,
  A) oxygen will diffuse out of the tissues into the blood.
  B) oxygen will diffuse into the tissues from the blood.
  C) carbon dioxide will diffuse into the tissues from the blood.
  D) there will be no diffusion of gases between the tissues and the blood.
  E) oxygen will be pumped from the blood into the tissues via active transport.



12. If the partial pressure of oxygen in the blood is lower than the partial pressure of oxygen in the body’s tissues,
  A) oxygen will diffuse out of the blood into the tissues.
  B) oxygen will diffuse into the blood from the tissues.
  C) carbon dioxide will diffuse into the blood from the tissues.
  D) there will be no diffusion of gases between the tissues and the blood.
  E) oxygen will be pumped from the blood into the tissues via active transport.



13. Suppose the partial pressure of oxygen is measured in a region of your body. The readings indicate that the partial pressure of oxygen in the blood is 40 mm Hg and the partial pressure of oxygen in the surrounding tissue is 100 mm Hg. The region where these readings were taken is most likely in your
  A) liver.
  B) skeletal muscle.
  C) heart.
  D) lungs.
  E) kidneys.



14. If oxygen is moving between a liquid and a gas, which factor is the most important in determining the direction in which that oxygen will diffuse?
  A) Difference in the concentration of the oxygen in the liquid and the gas
  B) Length of the diffusion path
  C) Difference in the partial pressure of the oxygen in the liquid and the gas
  D) Volume of the liquid
  E) Surface area of the liquid



15. The partial pressure of oxygen in a pond is lower than the partial pressure of oxygen in the air above the pond. The concentration of oxygen in the pond is higher than in the air. Under these conditions,
  A) the oxygen will move into the pond.
  B) the oxygen will move out of the pond.
  C) there will be no movement of oxygen.
  D) the oxygen will move concurrently with carbon dioxide.
  E) the oxygen will move into the trees surrounding the pond.



16. The rate at which a gas diffuses between two locations is _______ the distance between those locations.
  A) unrelated to
  B) positively related to
  C) the square root of
  D) inversely related to
  E) None of the above



17. August Krogh determined that the maximum distance over which O2 can flow across a tissue or tissue fluids and still meet the metabolic demands of the organism is
  A) 0.05 mm.
  B) 0.5 mm.
  C) 5.0 mm.
  D) 50.0 mm.
  E) 5.0 cm.



18. _______ describes bulk flow of air or water between the gas exchange membranes in an animal and the outside world.
  A) Diffusion
  B) Breathing
  C) External respiration
  D) Ventilation
  E) Cellular respiration



19. The gas exchange membranes of an animal consist of one to two layers of
  A) adipose tissue.
  B) epithelial tissue.
  C) nervous tissue.
  D) muscle.
  E) connective tissue.



20. Many tiny _______ are believed to breathe by diffusion rather than ventilation.
  A) amphibians
  B) birds
  C) fish
  D) mammals
  E) insects



21. Which statement about gills is false?
  A) The respiratory membrane has a large surface area.
  B) They are found in aquatic organisms.
  C) They are folded outward from the body.
  D) They are surrounded by the environmental medium.
  E) They contain the environmental medium.



22. Which animal exhibits unidirectional ventilation?
  A) Lobster
  B) Rabbit
  C) Frog
  D) Rattlesnake
  E) Turtle



23. Which animal exhibits tidal ventilation?
  A) Lobster
  B) Shark
  C) Catfish
  D) Planarian
  E) Turtle



24. Oxygen can be exchanged more easily in air than in water because
  A) more energy is required to move air than water.
  B) oxygen diffuses more rapidly in water than in air.
  C) the oxygen content of air is higher than that of water.
  D) air temperature is usually higher than water temperature.
  E) Both a and b



25. The table below shows data on oxygen concentration in water and the use of oxygen by fish at different water temperatures. What is one conclusion that can be drawn from these data?


  A) The solubility of oxygen in water increases as the temperature of the water increases.
  B) An inactive fish uses less oxygen during respiration when its body temperature is warmer.
  C) An active fish uses less oxygen than an inactive fish at higher water temperatures.
  D) Both active and inactive fish use oxygen at higher rates in warm water than they do in cold water.
  E) As water temperatures drop the amount of dissolved oxygen in the water decreases.



26. Rapid gas exchange can be accomplished more easily in air than in water because
  A) the O2 content of water is higher than that of air.
  B) the CO2 content of water is higher than that of air.
  C) O2 diffuses more rapidly in water than in air.
  D) water is more dense and viscous than air.
  E) more energy is required to move air than to move water.



27. Which is not an example of bulk flow of oxygen?
  A) Wind blowing
  B) Ventilation
  C) Water currents
  D) Flow of blood from the lungs through the blood vessels
  E) Movement of oxygen from the lungs into the blood stream



28. What would be an expected outcome of a drop in water temperature in a pond?
  A) An increase in the metabolism of fish living in the pond
  B) A decrease in the amount of O2 in the water
  C) Increased blood flow in the fish living in the pond
  D) Decreased O2 consumption of the fish living in the pond
  E) An increase in body temperature of the fish living in the pond



29. Aquatic animals that lack specialized internal organs for transporting respiratory gases
  A) may have flat, leaflike bodies.
  B) get rid of CO2 by diffusion.
  C) may have cells organized around extensive internal passageways through which water circulates.
  D) have cells that are all close to the respiratory medium.
  E) All of the above



30. Which group of animals lacks specialized breathing organs?
  A) Mammals
  B) Sponges
  C) Reptiles
  D) Insects
  E) Fish



31. Which statement about respiratory adaptations is false?
  A) Internalization of respiratory surfaces leads to the need for ventilation.
  B) External gills are found only in invertebrates.
  C) Some fishes ventilate their gills by swimming with their mouths open.
  D) In fish, water flows unidirectionally into the mouth, over the gills, and out from under the opercular flaps.
  E) Desiccation of the respiratory surface is more likely to occur in lungs than in gills.



32. The rate of gas exchange in mammals is maximized by
  A) an exceedingly high partial pressure of O2 in the blood.
  B) the opening of the larynx (voice box) into the trachea.
  C) an enormous surface area for gas exchange.
  D) the relatively small increase in size of the thoracic cavity during inhalation.
  E) the use of mucus as a surfactant.



33. Which group of animals has a respiratory system that involves countercurrent exchange?
  A) Mammals
  B) Sponges
  C) Reptiles
  D) Insects
  E) Fish



34. As water exits the gill cavity of fish,
  A) the partial pressure of oxygen is higher than when it entered.
  B) the partial pressure of oxygen is lower than when it entered.
  C) the partial pressure of carbon dioxide is lower than when it entered.
  D) it is colder than when it entered.
  E) it is completely depleted of oxygen.



35. The delicate gills of fishes are supported by _______ and _______.
  A) opercular flaps; gill arches
  B) opercular flaps; gill filaments
  C) gill filaments; gill arches
  D) opercular flaps; a diaphragm
  E) gill arches; a diaphragm



36. Which statement about the structure of the fish gill is false?
  A) Afferent vessels bring blood to the gills and efferent vessels take blood away from the gills.
  B) Exchange of respiratory gases occurs within the lamellae of the gill filaments.
  C) The efferent and afferent vessels are the countercurrent flow system of the gills.
  D) The lamellae greatly increase the surface area for gas exchange.
  E) The opercular flaps cover the gill chambers.



37. Which is not an adaptation seen in fish gills?
  A) A countercurrent exchange system
  B) Bidirectional ventilation
  C) Morphological features that increase the surface area available for gas exchange
  D) Morphological features that decrease the path length for diffusion of the respiratory gases
  E) Morphological features that maximize the efficiency of O2 extraction



38. Which is not one of the factors that accounts for the efficiency of gas exchange in fish gills?
  A) Maximized surface area
  B) Minimized path length for diffusion
  C) Countercurrent flow of blood and water over opposite sides of the gas exchange surfaces
  D) Great numbers of secondary lamellae
  E) One-way flow of water coming in through the gills and exiting through the mouth



39. Bird and fish respiratory systems are similar in that both
  A) employ a countercurrent exchanger.
  B) have air sacs.
  C) function by means of unidirectional flow of the environmental medium over the gas exchange membranes.
  D) consist of infoldings of the body.
  E) involve opercular flaps.



40. Which of the following characterizes the lungs of most terrestrial vertebrates?
  A) Air sacs
  B) Tidal ventilation
  C) Complete emptying in exhalation
  D) Crosscurrent airflow
  E) Countercurrent airflow



41. Which statement about lung surfactant is true?
  A) It is found in reptiles, amphibians, and mammals.
  B) It reduces the surface tension at the surfaces of lung epithelium.
  C) It is composed of proteins and lipids.
  D) It helps stabilize the three-dimensional structure of gas exchange membranes.
  E) All of the above



42. If a new air pollutant were to damage the surfactant in people’s lungs, one likely result would be
  A) decreased surface tension of the fluid lining their alveoli.
  B) increased uptake of CO2 from the environment.
  C) increased effort needed to breathe.
  D) decreased levels of hydrogen bonding in the fluid of their alveoli.
  E) Both a and c



43. The gas exchange system of _______ includes air sacs that interact with the lungs, and air flowing unidirectionally through parabronchi.
  A) insects
  B) fish
  C) amphibians
  D) mammals
  E) birds



44. Air sacs of the avian respiratory system can be grouped into _______ air sacs.
  A) lateral and ventral
  B) anterior and posterior
  C) posterior and ventral
  D) lateral and dorsal
  E) anterior and ventral



45. In the respiratory cycle of birds, inhaled air flows through the trachea, to the bronchi, and then
  A) into the parabronchi and posterior air sacs.
  B) back through the trachea.
  C) to the air capillaries.
  D) into the parabronchi and anterior air sacs.
  E) into the anterior air sacs.



46. In birds, upon exhalation, air sacs are _______, air passes through the _______, and it then passes out through the _______.
  A) filled with air; anterior air sac; bronchi
  B) contracted; posterior air sac; trachea
  C) expanded; parabronchi; bronchi
  D) compressed; lungs; trachea
  E) expanded; bronchi; trachea



47. Which statement about the air sacs of birds is false?
  A) They connect to airways in the lungs.
  B) They are structured as anterior and posterior pairs.
  C) They make the bird’s respiratory system more efficient than a mammal’s.
  D) They allow for one-way airflow through the lungs.
  E) They provide an extra gas exchange surface.



48. Which feature is similar in the respiratory systems of mammals and birds and distinguishes them from other terrestrial vertebrates?
  A) High efficiency to support high metabolic rates
  B) Unidirectional airflow
  C) Air sacs
  D) Parabronchi
  E) Lung flexibility



49. Which organism does not require both external ventilation of its respiratory surfaces with the medium containing O2 and internal ventilation of its respiratory surfaces with blood?
  A) Crayfish
  B) Rabbit
  C) Insect
  D) Fish
  E) Bird



50. The respiratory system of insects consists of
  A) branched air tubes called spiracles that supply capillaries.
  B) branched air tubes called tracheae that open to the atmosphere through spiracles.
  C) branching gill systems that end in openings called tracheae.
  D) branching gill systems that end in openings called spiracles.
  E) extensive layers of gas exchange tissue just under the exoskeleton.



51. Which statement about insect respiration is false?
  A) Spiracles are the internal air tubes that carry the respiratory gases.
  B) Because O2 diffuses more quickly in air than in water, the insect respiratory system is highly efficient.
  C) Tracheae have such extensive branching that they come close to every cell.
  D) Air sacs found in many insects can be used to ventilate the tracheae.
  E) Tracheae are lined with chitin.



52. Which structure(s) is/are a site of gas exchange in mammalian lungs?
  A) Pharynx
  B) Primary bronchi
  C) Secondary bronchi
  D) Trachea
  E) Alveoli



53. The _______ serve(s) as a joint passageway for air and food.
  A) alveoli
  B) bronchi
  C) bronchioles
  D) pharynx
  E) trachea



54. Which sequence represents the correct pathway of air during inhalation in mammals?
  A) Pharynx, larynx, trachea, bronchi, alveoli
  B) Larynx, trachea, pharynx, bronchi, alveoli
  C) Trachea, larynx, pharynx, bronchi, alveoli
  D) Trachea, larynx, pharynx, alveoli, bronchi
  E) Pharynx, trachea, bronchi, larynx, alveoli



55. In mammals, the respiratory structure(s) that carry air into the lungs is/are the
  A) bronchioles.
  B) larynx.
  C) trachea.
  D) secondary bronchi.
  E) primary bronchi.



56. Which structure is not part of the conducting airways in a mammal?
  A) Trachea
  B) Larynx
  C) Primary bronchi
  D) Respiratory bronchioles
  E) Secondary bronchi



57. If you are healthy, the blood and air in your alveoli are only about _______ mm apart, which promotes rapid diffusion of respiratory gases.
  A) 0.05
  B) 0.5
  C) 5.0
  D) 50.0
  E) 500.0



58. Which term represents the volume of your normal breath?
  A) Resting tidal volume
  B) Residual volume
  C) Respiratory minute volume
  D) Vital capacity
  E) Total lung capacity



59. In the following equation, which quantity represents the volume of your normal breath at rest?

Total lung capacity = residual volume + expiratory reserve volume + inspiratory reserve volume + tidal volume

  A) Total lung capacity
  B) Residual volume
  C) Expiratory reserve volume
  D) Inspiratory reserve volume
  E) Tidal volume



60. Maximal tidal volume is about _______ times the resting tidal volume.
  A) 2
  B) 6
  C) 10
  D) 12
  E) 20



61. Which statement about human breathing is true?
  A) It involves countercurrent gas exchange.
  B) With maximum inhalation, a person can breathe in as much air as the lungs can hold.
  C) A residual volume of air remains in the lungs even with maximum exhalation.
  D) There is a long diffusion path between the blood and the air (greater than 0.5 mm).
  E) The partial pressure of O2 within the alveoli is the same as that of the external air.



62. Which statement about human breathing is true?
  A) The volume of the thoracic cavity does not change.
  B) You contract all your intercostal muscles to help expel air from your lungs.
  C) You relax your diaphragm when you breathe in.
  D) For a person at rest, less energy is expended for exhalation than for inhalation.
  E) The thoracic cavity contracts during inhalation.



63. In mammals, centers in the brain that generate signals that control the rhythm of breathing are known as the
  A) diaphragms.
  B) pre-Bötzinger complexes.
  C) carotid bodies.
  D) aortic bodies.
  E) hypoglossal nuclei.



64. The caudal (posterior) side of the mammalian thoracic cavity is formed by the
  A) diaphragm.
  B) esophagus.
  C) stomach.
  D) ribs.
  E) intercostal muscles.



65. The lungs in mammals expand during inhalation because
  A) the diaphragm contracts upward.
  B) the shoulder girdle moves upward.
  C) the volume of the thoracic cavity increases.
  D) lung tissue actively stretches.
  E) the lung tissue rebounds from exhalation.



66. When you are at rest, the process of exhalation involves
  A) the contraction of all your intercostal muscles.
  B) elastic recoil of your lung tissues.
  C) the contraction of your diaphragm.
  D) complete collapse of your lung tissue.
  E) low pressure in your thoracic cavity.



67. If the thoracic wall is punctured, air leaking in will cause the lung to collapse. Thus one can conclude that in the normal intact thoracic cavity,
  A) lung expansion is passive.
  B) air pressure is the same as it is on the outside.
  C) air pressure is lower than it is on the outside, which helps keep the lungs inflated.
  D) breathing movements keep the lungs inflated.
  E) Both a and b



68. Breathing rhythm in mammals is generated in the
  A) medulla oblongata.
  B) lungs.
  C) diaphragm.
  D) frontal lobe.
  E) cerebellum.



69. The partial pressure of CO2 in the blood is monitored carefully by the human body, and any changes lead quickly to changes in respiratory rate. Both an increase in partial pressure of CO2 and _______ are stimuli that lead to increased respiratory gas exchange.
  A) an increase in the partial pressure of N2 in the blood
  B) a decrease in the partial pressure of O2 in the blood
  C) the temperature as measured at the hypothalamus
  D) increased acidity in the blood
  E) a lowered pulse rate



70. The breathing centers in humans initiate ventilation in response to
  A) a decrease in air pressure.
  B) a decrease in O2 partial pressure in the blood.
  C) an increase in CO2 partial pressure in the blood.
  D) the time since the last breath.
  E) the rate of gas exchange in the alveoli.



71. In studies of dogs running on treadmills, a researcher found that when the dogs were running at 3 mph, the average value of CO2 partial pressure was 39.0 mm Hg and the average respiratory minute volume in L/min was 9.0. The treadmill speed was then increased to 6 mph; the initial recordings are shown in the tables below. You can conclude from these data that when the dogs started running at twice the speed, their


  A) arterial CO2 partial pressure was relatively unchanged.
  B) arterial CO2 partial pressure increased exponentially by a power of 2.
  C) respiratory rate increased.
  D) respiratory rate was unchanged.
  E) Both a and c



72. In studies of dogs running on treadmills, results stemming from a gradual increase in the slope of the treadmills supported the hypothesis that the partial pressure of CO2 is the feedback signal controlling respiratory rate. However, a related experiment that did not support that hypothesis
  A) compared respiratory rates of dogs versus cats.
  B) compared sleeping versus barking dogs.
  C) changed the speed at which the dogs ran instead of the slope of the treadmills.
  D) changed the dogs’ motivation by keeping them food-stressed.
  E) involved the injection of dissolved O2 into the dogs’ arteries.



73. In mammals, nodes that are sensitive to O2 and blood pressure levels are located in the
  A) aorta and carotid arteries.
  B) brain stem capillaries.
  C) hypothalamus.
  D) pulmonary artery.
  E) pulmonary vein.



74. The carotid and aortic bodies of mammals
  A) respond to significant drops in the blood O2 partial pressure.
  B) are blood vessels.
  C) detect minor fluctuations in heart rate.
  D) are electrosensors.
  E) are located in the left ventricle of the heart.



75. In mammals, neural control of breathing is a function of the
  A) cerebrum.
  B) diaphragm.
  C) medulla oblongata.
  D) olfactory lobe.
  E) spinal cord.



76. Chemoreceptors on the surface of the medulla oblongata are sensitive to
  A) O2.
  B) N2.
  C) surfactant.
  D) blood CO2 partial pressure and pH.
  E) None of the above



77. Which is not an important factor in the control of ventilation rate?
  A) Small changes in blood O2 partial pressure
  B) Small changes in blood CO2 partial pressure
  C) Blood pH
  D) The medulla oblongata
  E) Receptors detecting motion in muscle and joints



78. Since there are no active transport mechanisms for respiratory gases, they can be exchanged only by _______.



79. In a mixture of gases, the portion of the total pressure exerted by any particular gas is called the _______.



80. In Fick’s law of diffusion, the formula (P1P2) refers to the difference in the _______ of a gas at two locations.



81. If the distance (L) of the diffusion path length is increased, the rate of diffusion will _______.



82. The bulk flow of air or water between the gas exchange membranes and the outside world is called _______.



83. External _______ are highly branched folds of the body surface that are involved in gas exchange.



84. Breathing mechanisms (ventilate/perfuse) _______ the environmental side of the gas exchange surface, while circulatory systems (ventilate/perfuse) _______ the internal side of the surface.



85. In fish gas exchange systems, blood flows through gill lamellae in a direction opposite to water flow, a phenomenon known as _______.



86. Among vertebrates, _______ have the most efficient lungs.



87. An unusual feature of the lungs of birds is that they do not change much in _______ during inhalation and exhalation.



88. Vertebrate lungs produce _______, a substance that reduces the surface tension of the liquid lining the insides of the alveoli.



89. In addition to possessing lungs, birds have _______ at several locations in their bodies that function in the respiratory system.



90. The internal breathing tubes of insects are called _______.



91. If you trace the path of a molecule of oxygen as you inhale, you would see that it enters the _______ immediately after leaving the trachea.



92. The branches of the mammalian airway system that are not involved in gas exchange are called the _______.



93. The membranes that line the thoracic cavity and also cover the lungs are called the _______ membranes.



94. In the mammalian lung, the volume of air that is moved in normal breathing is called the _______.



95. In adult humans, the resting tidal volume, on average, is about _______.



96. After extreme exhalation, the lungs and airways still contain a(n) _______ volume of air.



97. In mammals, a small increase of _______ in the bloodstream stimulates a large increase in ventilation.



98. In mammals, a large drop in arterial _______ partial pressure has a small effect on breathing rate.



99. Our sensors for detecting the partial pressure of O2 in the blood are located in blood vessels leaving the _______.



100. It is common knowledge that we get the oxygen we inhale from photosynthetic organisms that release it into our atmosphere. Where does the carbon dioxide we exhale come from?



101. The partial pressure of O2 in the air above a lake is 140 mm Hg, while the partial pressure of O2 in the lake is 144 mm Hg. The concentration of O2 in the lake is lower than the concentration of O2 in the air. Based on your understanding of Fick’s law, which way will the oxygen molecules move? Explain your answer.



102. Give an example of an animal most likely to use tidal ventilation, and compare it to an animal most likely to use unidirectional ventilation.



103. Many ocean fish depend on the phenomenon of upwelling, in which cold, nutrient-rich water rises up from the depths to mix with warm, nutrient-poor water near the surface. What are the likely effects of these upwellings on fish respiration? How would the effects of global warming potentially affect the survival of aquatic species?



Use the following to answer questions 104-105:


Refer to the diagram below of Nathan Miller’s experiments with loggerhead sea turtle eggs in which he measured the partial pressure of oxygen in a nest that was buried in the sand on an ocean beach.




104. On what day did the nest get flooded with seawater?



105. If seawater contains oxygen, why did the partial pressure of oxygen drop in the nest when the nest was flooded?



106. If you were a research scientist tasked with designing an artificial respiratory system in the lab, what would be the most important factors to incorporate into your design and why?



Use the following to answer questions 107-108:


Refer to the diagram below of a countercurrent exchanger from a fish gill. The values represent O2 partial pressure (in arbitrary units).




107. Based on this information alone, which tube represents the flow of water and which represents the flow of blood?



108. Based on this information alone, which direction is the blood flowing in its tube and which way is the water flowing in its tube?



109. Using the diagram below as your guide, describe the airflow during inhalation of birds.




110. Think about the path traveled by a molecule of oxygen you inhale. Name, in order, each structure the molecule of oxygen passes through on its journey to your alveoli.



Use the following to answer questions 111-112:


Refer to the diagram below showing a spirometer’s measurement of lung ventilation in an individual.




111. Which numbered arrow on the spirometer tracing is associated with resting tidal volume? Total lung capacity? Residual volume?



112. Based on the measurements shown in the graph, what is the vital capacity of this individual?



113. Does the diagram below show the process of inhalation or exhalation? Which details in the diagram support your conclusion?




114. Which respiratory gas is the major factor in controlling breathing rates in mammals, and how is it detected?



115. How and where is the partial pressure of oxygen in the blood detected?




Answer Key


1. B
2. E
3. D
4. D
5. A
6. C
7. B
8. D
9. C
10. A
11. B
12. B
13. D
14. C
15. A
16. D
17. B
18. D
19. B
20. E
21. E
22. A
23. E
24. C
25. D
26. D
27. E
28. D
29. E
30. B
31. B
32. C
33. E
34. B
35. A
36. C
37. B
38. E
39. C
40. B
41. E
42. C
43. E
44. B
45. A
46. D
47. E
48. A
49. C
50. B
51. A
52. E
53. D
54. A
55. E
56. D
57. B
58. A
59. E
60. C
61. C
62. D
63. B
64. A
65. C
66. B
67. C
68. A
69. D
70. C
71. E
72. C
73. A
74. A
75. C
76. D
77. A
78. diffusion
79. partial pressure
80. partial pressure
81. decrease
82. ventilation
83. gills
84A. ventilate
84B. perfuse
85. countercurrent exchange
86. birds
87. volume
88. surfactant
89. air sacs
90. tracheae
91. primary bronchi
92. conducting airways (or trachea, bronchi, and conducting bronchioles)
93. pleural
94. tidal volume
95. 500 ml (or 0.5 liter)
96. residual
97. CO2 (or carbon dioxide, or H+, or acidity)
98. O2
99. heart
100. Carbon dioxide is a by-product of cellular respiration—specifically, the citric acid cycle.
101. The oxygen will move out of the water into the air. Fick’s law states that when oxygen is moving between gas and liquid phases, it will move from a location of higher partial pressure to a location of lower partial pressure regardless of concentration levels.
102. (Answers will vary.) A rabbit would use tidal ventilation because the structure of their lungs makes unidirectional ventilation impossible. Animals with gills, like fish, by contrast, typically move water over the gills using unidirectional ventilation.
103. Upwellings are beneficial because the cooler water has more oxygen available for the fish. Warming oceans would be detrimental to aquatic species because as temperatures rise, metabolic activity of the fish (and thus oxygen demand) increases, while the amount of available oxygen decreases.
104. Around day 50
105. The partial pressure of oxygen in the nest depends upon how fast the developing turtles use the oxygen and how fast the oxygen is replenished by diffusion from the atmosphere. When the nest was dry, diffusion of oxygen through the dry sand was fast enough to keep the partial pressure of oxygen high. But diffusion of oxygen takes place at a much slower rate through water than it does through air, and the solubility of oxygen is much lower in water than in air. So when the nest became flooded, the turtles were using oxygen faster than it could be replaced by diffusion through the water-soaked sand, dropping the oxygen partial pressure in the nest to zero.
106. The respiratory system needs to have a large surface area with thin respiratory membranes. Fick’s law supports these two factors as being of utmost importance.
107. Tube A‒B is water and tube C‒D is blood.
108. The blood flows from C to D; the water flows from B to A.
109. The air moves into the trachea and then into the posterior air sacs and up into the parabronchi, where it travels to the anterior air sacs.
110. The nostrils and/or mouth, nasal cavity (and oral cavity), pharynx, larynx, trachea, primary bronchi, secondary bronchi, bronchioles (or respiratory bronchioles), and alveoli
111. 2; 6; 4
112. About 5 liters (or 5,000 ml)
113. Inhalation. During inhalation, the diaphragm contracts and moves down, some of the intercostal muscles contract expanding the thoracic cavity, and the lungs expand to the walls of the thoracic cavity.
114. Carbon dioxide levels (and blood pH) determine the breathing rate in mammals. They are detected by chemosensors in the medulla oblongata (or pre-Bötzinger complexes).
115. The carotid and aortic bodies (chemosensors) detect the partial pressure of oxygen in the blood. They are found along the carotid arteries in the neck and associated with the aorta, respectively.


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