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51) Which of the following processes is classified as a metabolic pathway?
A) protein synthesis
B) osmosis
C) cell lysis
D) passive diffusion
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
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.
54) The transfer of a phosphate group to a molecule or compound is called
A) carboxylation.
B) ionization.
C) phosphorylation.
D) hydrogenation.
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.
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.
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.
58) The energy required to initiate an exergonic reaction is called
A) exergonic energy.
B) endergonic energy.
C) input energy.
D) activation energy.
59) Most of a cell's enzymes are
A) lipids.
B) proteins.
C) amino acids.
D) carbohydrates.
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.
61) Substrates bind to an enzyme's ________ site.
A) allosteric
B) inhibitory
C) phosphate
D) active
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.
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.
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.
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.
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.
67) Which of the following substances could be a cofactor?
A) a protein
B) a polypeptide
C) a zinc atom
D) a ribosome
68) Which of the following is a coenzyme?
A) zinc
B) vitamin B6
C) iron
D) iodine
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.
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.
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.
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.
73) A group of single cell organisms collected from the ocean was brought into the lab for
examination. The lab assistant was concerned that the water had become full of toxic waste
products and so added clean water to the culture. All of the organisms died, and when she looked
at them under the microscope, all she could see were bits and pieces of them scattered
throughout the water. What likely happened?
A) She added water that was hypotonic to the culture of organisms, and they ruptured.
B) She added sea water to which she had added too much salt, and they ruptured.
C) She added water isotonic to the organisms, causing too much water to move in and out of the
organism, and they ruptured.
D) She added too little salt to the sea water she added, and the organisms all lost too much water
and shriveled up.
5.2 Art Questions
1) Which figure depicts an animal cell placed in a solution hypotonic to the cell?
A) cell A
B) cell B
C) cell C
D) cell D
2) Which part of the ATP molecule breaks free of the rest when an ATP molecule is used for
energy?
A) part A
B) part B
C) part C
D) part D
22
Figure A. Changes in permeability of tubules in the kidney in response to the hormone
vasopressin (AVP), which aids in osmoregulation.
Figure B. Density of aquaporins in kidney tubule cells before, during, and after administration of
vasopressin.
Figure C. Permeability of tissues to water before, during, and after administration of vasopressin.
The following questions relate to these data indicating how the tubules in the kidney respond to
the administration of the hormone vasopressin.
3) Using the data from the graphs and what you know about membranes and metabolic
pathways, predict which of the following is the likely reason why actions of aquaporins in a
membrane can change so rapidly.
A) The number of aquaporins in the membrane is constant, but the pores have to be activated.
B) Aquaporins are inserted into the membrane as needed.
C) Aquaporins are only in cells that need to be permeable to water.
D) Aquaporins use ATP to pump water across the membrane, and their action is limited by the
metabolic pathways that produce ATP.
4) How do the data in Figure A relate to the data in Figures B and C?
A) Figure B shows the method used to obtain the data in Figure A.
B) Figure C is essentially a summary of the data in Figure A.
C) Figure A is about water movement, and Figures B and C are about presence of aquaporins.
D) Figure A has data for more than 2 hours, and Figures B and C show data all collected at the
same time.
5.3 Scenario Questions
After reading the paragraph below, answer the questions that follow.
Americans spend up to $100 billion annually for bottled water (41 billion gallons). The only
beverages with higher sales are carbonated soft drinks. Recent news stories have highlighted the
fact that most bottled water comes from municipal water supplies (the same source as your tap
water), although it may undergo an extra purification step called reverse osmosis.
Imagine two tanks that are separated by a membrane that's permeable to water, but not to the
dissolved minerals present in the water. Tank A contains tap water and tank B contains the
purified water. Under normal conditions, the purified water would cross the membrane to dilute
the more concentrated tap water solution. In the reverse osmosis process, pressure is applied to
the tap water tank to force the water molecules across the membrane into the pure water tank.
1) After the reverse osmosis system has been operating for 30 minutes, the solution in tank A
would
A) be hypotonic to tank B.
B) be isotonic to tank B.
C) be hypertonic to tank B.
D) move by passive transport to tank B.
2) If you shut off the system and pressure was no longer applied to tank A, you would expect
A) the water to flow from tank A to tank B.
B) the water to reverse flow from tank B to tank A.
C) the water to flow in equal amounts in both directions.
D) the water to flow against the concentration gradient.
3) Water that is filtered out of the blood by the kidneys is returned to the body through the action
of aquaporins. Which of the following statements about water balance disorders is scientifically
accurate?
A) People with heart failure often swell due to too much water from excess numbers of
aquaporins.
B) Water retention (too much water) in pregnancy can be due to a decreased number of
aquaporins.
C) Kidney failure and decreased urine production are due to increased numbers of aquaporins.
D) Small amounts of urine are produced by people who inherit a defect in the ability to make
aquaporins.
