CHAPTER 5

45) According to ________, energy cannot be created or destroyed. A) Aristotle's first principle B) the first law of thermodynamics C) the second law of thermodynamics D) the third law of thermodynamics

B

46) A steer must eat at least 100 pounds of grain to gain less than 10 pounds of muscle tissue. This illustrates A) the first law of thermodynamics. B) the second law of thermodynamics. C) that some energy is destroyed in every energy conversion. D) that energy transformations are typically 100% efficient.

B

49) Which of the following processes is endergonic? A) the burning of wood B) the synthesis of glucose from carbon dioxide and water C) the breakdown of glucose D) cellular respiration

B

59) Most of a cell's enzymes are A) lipids. B) proteins. C) amino acids. D) carbohydrates.

B

6) Aspirin and other nonsteroidal anti-inflammatory drugs (NSAID)inhibit inflammation by inhibiting an enzyme in the prostaglandin pathway, but by inhibiting this enzyme and this pathway they also inhibit pathways that protect the stomach from damage by stomach acid and that prevent aggregation of blood platelets to form blood clots. What can you conclude from this? A) The enzyme inhibition is nonreversible. B) The enzyme is found in many different types of cells. C) Prostaglandins cause blood clotting. D) Aspirin should not be given to people who people who need to synthesize enzymes.

B

65) A child is brought to the hospital with a fever of 107°F. Doctors immediately order an ice bath to lower the child's temperature. Which of the following statements offers the most logical explanation for this action? A) Elevated body temperature will increase reaction rates in the child's cells and overload the limited number of enzymes found in the cell. B) Elevated body temperatures may denature enzymes. This would interfere with the cell's abilities to catalyze various reactions. C) Elevated body temperatures will increase the energy of activation needed to start various chemical reactions in the body. This will interfere with the ability of enzymes to catalyze vital chemical reactions. D) Elevated body temperatures cause molecules to vibrate more quickly and prevent enzymes from easily attaching to reactants. This would slow vital body reactions.

B

68) Which of the following is a coenzyme? A) zinc B) vitamin B6 C) iron D) iodine

B

7) Most of the functions of a cell membrane, including transport and enzymatic function, are performed by A) glycolipids. B) proteins. C) phospholipids. D) cholesterol.

B

14) Small, nonpolar, hydrophobic molecules such as fatty acids A) easily pass through a membrane's lipid bilayer. B) very slowly diffuse through a membrane's lipid bilayer. C) require transport proteins to pass through a membrane's lipid bilayer. D) are actively transported across cell membranes.

A

19) Osmosis can be defined as A) the diffusion of water. B) the diffusion of nonpolar molecules. C) active transport. D) the diffusion of a solute.

A

20) When two aqueous solutions that differ in solute concentration are placed on either side of a semipermeable membrane and osmosis is allowed to take place, the water will A) exhibit a net movement to the side with lower free water concentration. B) exhibit a net movement to the side with higher free water concentration. C) exhibit a net movement to the side with lower solute concentration. D) exhibit an equal movement in both directions across the membrane.

A

21) In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. Which of the following will occur? A) Water will leave the balloon. B) Water will enter the balloon. C) Sucrose will leave the balloon. D) Sucrose will enter the balloon.

A

23) A cell that has neither a net gain of water nor net loss of water when it is immersed in a solution must be A) isotonic to its environment. B) hypertonic to its environment. C) hypotonic to its environment. D) metabolically inactive.

A

24) In a hypotonic solution, an animal cell will A) lyse. B) experience turgor. C) neither gain nor lose water. D) shrivel.

A

28) A plant cell in a hypotonic solution A) becomes turgid because of an inflow of water. B) bursts because of an inflow of water. C) shrivels because of an outflow of water. D) wilts because of an outflow of water.

A

33) Aquaporins A) allow water to cross the plasma membrane via facilitated diffusion. B) allow water to cross the plasma membrane against its concentration gradient. C) allow for the active transport of water. D) are found in all cells.

A

42) Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing A) chemical energy into kinetic energy. B) chemical energy into potential energy. C) kinetic energy into potential energy. D) kinetic energy into thermal energy.

A

51) Which of the following processes is classified as a metabolic pathway? A) protein synthesis B) osmosis C) cell lysis D) passive diffusion

A

55) Anything that prevents ATP formation will most likely A) result in cell death. B) force the cell to rely on lipids for energy. C) force the cell to rely on ADP for energy. D) have no effect on the cell.

A

15) Which of the following substances would have the most trouble crossing a biological membrane by diffusing through the lipid bilayer? A) O2 B) CO2 C) Na+ D) a small, nonpolar molecule such as butane (C4H10)

C

17) Which of the following statements regarding diffusion is false? A) Diffusion is a result of the thermal energy of atoms and molecules. B) Diffusion requires no input of energy into the system. C) Diffusion occurs when particles spread from areas where they are less concentrated to areas where they are more concentrated. D) Diffusion occurs even after equilibrium is reached and no net change is apparent.

C

27) White blood cells (WBCs) are more resistant to lysis than red blood cells (RBCs). When looking at a sample of blood for WBCs, what could you do to reduce interference from RBCs? A) Mix the blood in a salty solution to cause the RBCs to lyse. B) Mix the blood in an isotonic solution and allow the WBCs to float to the top. C) Mix the blood in a hypotonic solution, which will cause the RBCs to lyse. D) Mix the blood in a hypertonic solution, which will cause the RBCs to lyse.

C

54) The transfer of a phosphate group to a molecule or compound is called A) carboxylation. B) ionization. C) phosphorylation. D) hydrogenation.

C

70) Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline. This is an example of A) competitive inhibition. B) noncompetitive inhibition. C) feedback inhibition. D) irreversible inhibition.

C

72) A man with a dirty cut on his hand appears at the emergency department for treatment. In order to clean the wound, the health-care provider should use A) a solution of very low pH to help kill any bacteria present. B) a solution of sterilized tap water. C) a weak (low concentration) solution of salt water. D) distilled water.

C

11) Which of the following statements regarding membrane function is false? A) The plasma membrane forms a selective barrier around the cell. B) The plasma membrane plays a role in transferring signals to the cell's interior. C) The plasma membrane has receptors for chemical messages. D) The plasma membrane is the control center of the cell.

D

13) All cells are enclosed by a plasma membrane that is similar in ________ and ________. A) thickness; composition B) permeability; content C) lucidity; texture D) structure; function

D

16) Oxygen crosses a plasma membrane by A) osmosis. B) active transport. C) pinocytosis. D) passive transport.

D

31) The molecules responsible for membrane transport are A) steroids. B) phospholipids. C) carbohydrates. D) proteins.

D

71) Inhibition of an enzyme is irreversible when A) a competitive inhibitor is involved. B) a noncompetitive inhibitor is involved. C) the shape of the enzyme is changed. D) covalent bonds form between inhibitor and enzyme

D

8) Which of the following statements regarding membrane protein function is false? A) Membrane proteins serve as enzymes. B) Membrane proteins act as receptors to molecules like hormones. C) Membrane proteins form junctions between cells. D) Membrane proteins transfer genetic information to the cytoplasm.

D

60) When an enzyme catalyzes a reaction, A) it lowers the activation energy of the reaction. B) it raises the activation energy of the reaction. C) it acts as a reactant. D) it is used once and discarded.

A

5) If you were working for a pharmaceutical company as part of a drug discovery team, which of these enzyme inhibitors would you suggest as a productive avenue for drug development? A) a drug to treat high blood pressure that reversibly inhibits an enzyme catalyzing production of a chemical that causes blood vessels to contract B) a drug to treat diabetes that irreversibly inhibits an enzyme in the metabolic pathway to synthesize glucose C) a compound that acts as a competitive inhibitor for a digestive enzyme produced only in the presence of certain foods D) a compound that inhibits enzymes by significantly changing the pH throughout the body

A

52) When a cell uses chemical energy to perform work, it uses the energy released from a(n) ________ reaction to drive a(n) ________ reaction. A) exergonic; endergonic B) endergonic; exergonic C) exergonic; spontaneous D) spontaneous; exergonic

A

9) Relaying a message from a membrane receptor to a molecule that performs a specific function within a cell occurs when A) a signaling molecule binds to a protein that extends to the outside of the cell. B) a protein receptor on the interior of the membrane become bounds by a signaling molecule. C) the extracellular matrix is moved to the inside of the cell. D) glycoproteins are recognized by other cells.

A

40) Cells acquire low-density lipoproteins (LDLs) by A) diffusion. B) receptor-mediated endocytosis. C) pinocytosis. D) phagocytosis.

B

1) Many physiological conditions are related to particular proteins in cell membranes. The number of insulin receptors in membranes is related to the amount of insulin present around those cells. If the presence of increased insulin results in a decrease in receptors and a decrease in insulin results in an increase in insulin receptors, this would be an example of A) a metabolic pathway. B) negative or regulatory feedback. C) passive transport. D) competitive inhibition.

B

10) Plasma membranes are selectively permeable. This means that A) anything can pass into or out of a cell as long as the membrane is intact and the cell is healthy. B) the plasma membrane allows some substances to enter or leave a cell more easily than others. C) glucose cannot enter the cell. D) plasma membranes must be very thick.

B

12) Which characteristic promoted the utilization of lipids as the first cell membrane? A) spontaneous degradation of the intracellular environment B) self-assembly into a simple membrane C) ability to form an impermeable membrane D) formation of a semi-solid membrane

B

18) Diffusion does not require the cell to expend ATP. Therefore, diffusion is considered a type of A) exocytosis. B) passive transport. C) active transport. D) endocytosis.

B

22) Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment A) is isotonic to the protozoan. B) is hypotonic to the protozoan. C) contains a higher concentration of solutes than the protozoan. D) is hypertonic to the protozoan.

B

26) In the lab, you use a special balloon that is permeable to water but not sucrose to make an "artificial cell." The balloon is filled with a solution of 20% sucrose and 80% water and is immersed in a beaker containing a solution of 40% sucrose and 60% water. The solution in the balloon is ________ relative to the solution in the beaker. A) isotonic B) hypotonic C) hypertonic D) hydrophilic

B

30) Facilitated diffusion across a biological membrane requires ________ and moves a substance ________ its concentration gradient. A) energy and transport proteins; down B) transport proteins; down C) energy and transport proteins; against D) transport proteins; against

B

32) Which of the following statements is true for all types of passive transport? A) Proteins are needed to transport molecules across the membrane. B) The concentration gradient is the driving force. C) Only small polar molecules are able to cross the plasma membrane. D) Ions never cross the plasma membrane by passive transport.

B

37) Certain cells that line the stomach synthesize a digestive enzyme and secrete it into the stomach. This enzyme is a protein. Which of the following processes could be responsible for its secretion? A) endocytosis B) exocytosis C) diffusion D) pinocytosis

B

4) The cholesterol associated with animal cell membranes A) is attached to membrane proteins and extends into the watery environment surrounding the cell. B) helps to keep phospholipids from being too close to one another. C) is an abnormality resulting from a diet high in cholesterol. D) helps solidify the membranes when the room temperature is below freezing.

B

29) You are adrift in the Atlantic Ocean and, being thirsty, drink the surrounding seawater. As a result, A) you quench your thirst. B) your cells become turgid. C) you dehydrate yourself. D) your cells lyse from excessive water intake.

C

3) Membrane phospholipids A) have hydrophobic heads that face the center of the membrane and are shielded from water. B) have hydrophilic tails that face outward and are exposed to water. C) are able to drift about in the plasma membrane. D) remain fluid because they are tightly packed against one another.

C

41) Kinetic energy differs from chemical energy in that A) kinetic energy is stored energy that has the potential to do work, and chemical energy is the energy of movement. B) kinetic energy can be converted into various forms of energy, whereas chemical energy can only be converted into heat. C) kinetic energy is the energy of a moving object, whereas chemical energy is the potential energy of molecules. D) chemical energy is a particular form of kinetic energy.

C

43) In the reaction A → B + C + heat, A) there is a net input of energy. B) the potential energy of the products is greater than that of the reactant. C) the potential energy of the products is less than that of the reactant. D) entropy has decreased.

C

48) Living systems A) violate the first law of thermodynamics. B) violate the second law of thermodynamics. C) decrease their entropy while increasing the entropy of the universe. D) are examples of a closed system.

C

50) What is the basic difference between exergonic and endergonic reactions? A) Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds. B) Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds. C) Exergonic reactions release energy; endergonic reactions absorb it. D) In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.

C

56) ATP can be used as the cell's energy exchange mechanism because A) endergonic reactions can be fueled by coupling them with the formation of ATP from ADP. B) ATP is the most energy-rich small molecule in the cell. C) endergonic reactions can be fueled by coupling them with the hydrolysis of high-energy phosphate bonds in ATP. D) ATP is a disposable form of chemical energy, used once and then discarded by the cell.

C

57) An energy barrier A) is the amount of energy that must be produced by the reactants to end a chemical reaction. B) is higher than the activation energy of a reaction. C) prevents the spontaneous breakdown of molecules in the cell. D) can only be overcome with the use of enzymes.

C

62) The active site of an enzyme is A) the region of a substrate that is changed by an enzyme. B) the highly changeable portion of an enzyme that adapts to fit the substrates of various reactions. C) the region of an enzyme that attaches to a substrate. D) the region of a product that detaches from the enzyme.

C

63) Which of the following statements regarding enzyme function is false? A) An enzyme's function depends on its three-dimensional shape. B) Enzymes are very specific for certain substrates. C) Enzymes are used up when they catalyze a chemical reaction so must be synthesized for each new chemical reaction. D) Enzymes emerge unchanged from the reactions they catalyze.

C

64) Which of the following statements regarding enzymes is true? A) Enzymes are inorganic. B) An enzyme's function is unaffected by changes in pH. C) Enzymes catalyze specific reactions. D) All enzymes depend on protein cofactors to function.

C

67) Which of the following substances could be a cofactor? A) a protein B) a polypeptide C) a zinc atom D) a ribosome

C

2) The fluid mosaic model describes the plasma membrane as consisting of A) a phospholipid bilayer with embedded carbohydrates. B) two layers of phospholipids with cholesterol sandwiched between them. C) carbohydrates and phospholipids that can drift in the membrane. D) diverse proteins embedded in a phospholipid bilayer.

D

25) If placed in tap water, an animal cell will undergo lysis, whereas a plant cell will not. What accounts for this difference? A) the expulsion of water by the plant cell's central vacuole B) the relative impermeability of the plant cell wall to water C) the fact that plant cells are isotonic to tap water D) the relative inelasticity and strength of the plant cell wall

D

34) Which of the following processes can move a solute against its concentration gradient? A) osmosis B) passive transport C) facilitated diffusion D) active transport

D

35) Which of the following is a typical feature of an ATP-driven active transport mechanism? A) The transport protein must cross to the correct side of the membrane before the solute can bind to it. B) The transport protein is irreversibly phosphorylated as transport takes place. C) The transport protein catalyzes the conversion of ADP to ATP. D) The solute moves against the concentration gradient.

D

36) Which of the following statements regarding active transport is false? A) Active transport uses ATP as an energy source. B) Active transport can move a solute against its concentration gradient. C) Active transport requires the cell to expend energy. D) Active transport is driven by the concentration gradient.

D

38) The process of a white blood cell engulfing a bacterium is A) osmosis. B) receptor-mediated endocytosis. C) pinocytosis. D) phagocytosis

D

44) Which of the following statements regarding thermodynamics is false? A) Thermodynamics is the study of energy transformations that occur in a collection of matter. B) A single cell or the planet Earth could be a thermodynamic system. C) An open system exchanges both energy and matter with its surroundings. D) An automobile engine is a closed system because it does not exchange energy and matter with its surroundings.

D

47) Which of the following direct energy transfers is impossible in living systems? A) light energy to chemical energy B) chemical energy to kinetic energy C) light energy to potential energy D) heat to light energy

D

53) Which of the following statements about the ATP molecule is true? A) It contains five phosphate groups. B) Extremely stable bonds link the second and third phosphate groups. C) It contains the sugar glucose. D) It releases energy when one phosphate group leaves ATP.

D

58) The energy required to initiate an exergonic reaction is called A) exergonic energy. B) endergonic energy. C) input energy. D) activation energy.

D

61) Substrates bind to an enzyme's ________ site. A) allosteric B) inhibitory C) phosphate D) active

D

66) Heating inactivates enzymes by A) breaking the covalent bonds that hold the molecule together. B) removing phosphate groups from the enzyme. C) causing enzyme molecules to stick together. D) changing the enzyme's three-dimensional shape.

D

69) How does inhibition of an enzyme-catalyzed reaction by a competitive inhibitor differ from inhibition by a noncompetitive inhibitor? A) Competitive inhibitors interfere with the enzyme; noncompetitive inhibitors interfere with the reactants. B) Competitive inhibitors bind to the enzyme reversibly; noncompetitive inhibitors bind to it irreversibly. C) Competitive inhibitors change the enzyme's tertiary structure; noncompetitive inhibitors cause polypeptide subunits to dissociate. D) Competitive inhibitors bind to the active site of the enzyme; noncompetitive inhibitors bind to a different site.

D

39) Phagocytosis is to eating as pinocytosis is to A) osmosis. B) drinking. C) chewing. D) lysis.

b