) Which of the following has the greatest amount of kinetic energy?
- A) A tank of gasoline
- B) A moving car
- C) A hot car engine
- D) The cool air surrounding the car engine
- E) An unlit firecracker
Answer: B
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
2) Which of the following does NOT have much potential energy?
- A) A water droplet at the top of a waterfall
- B) A glucose molecule
- C) A diver on a springboard
- D) A 9-V battery
- E) A ball that has rolled downhill and stopped
Answer: E
Diff: 2
Section: 6.1
Skill: Application/Analysis
3) All of the following statements are true of the first law of thermodynamics EXCEPT:
- A) the amount of useful energy decreases.
- B) the first law of thermodynamics is often called the law of the conservation of energy.
- C) the total amount of energy within an isolated system remains the same.
- D) one form of energy may be converted to a different form of energy.
Answer: A
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
4) In an isolated system, all of the following are true of the second law of thermodynamics EXCEPT:
- A) the amount of useful energy decreases.
- B) reactions cause energy to be converted from more useful to less useful forms.
- C) all chemical reactions release more energy than they consume.
- D) there is a natural tendency toward greater disorder of the organization of matter.
Answer: C
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
5) Entropy is a measure of an increase in
- A) orderliness.
- B) high-level energy.
- C) potential energy.
- D) randomness.
- E) kinetic energy.
Answer: D
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
6) How is your body able to work against the effects of entropy?
- A) Regular exercise
- B) Sunbathing
- C) Eating a balanced diet
- D) Regular work
Answer: C
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
7) Each of the following requires 12 carbon atoms. Which of the arrangements of carbon atoms has the greatest entropy?
- A) 12 molecules of carbon dioxide, CO2
- B) 1 molecule of the disaccharide maltose, C12H22O11
- C) 2 molecules of the monosaccharide glucose, C6H12O6
- D) 4 molecules of the monosaccharide pyruvate, C3H4O3
Answer: A
Diff: 3
Section: 6.1
Skill: Application/Analysis
8) Energy that is not converted to useful energy is usually given off as
- A) radioactivity.
- B) electricity.
- C) light.
- D) heat.
- E) entropy.
Answer: D
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
9) During photosynthesis, plants convert light energy to chemical energy. This is an example of
- A) increasing entropy.
- B) chemical equilibrium.
- C) the first law of thermodynamics.
- D) the second law of thermodynamics.
- E) a spontaneous reaction.
Answer: C
Diff: 2
Section: 6.1
Skill: Application/Analysis
10) Similar to a car, a human body is about ________ efficient in converting chemical energy to movement.
- A) 1%
- B) 25%
- C) 75%
- D) 95%
Answer: B
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
11) Which of the following is part of the first law of thermodynamics?
- A) Energy cannot be created or destroyed.
- B) Kinetic energy is stored energy.
- C) Energy cannot be transferred or transformed.
- D) Exergonic reactions are coupled with endergonic reactions.
- E) Potential energy equals kinetic energy in a reaction.
Answer: A
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
12) How is it possible for living organisms to comply with the second law of thermodynamics?
- A) Chemical reactions inside cells mostly cause an increase in high-level energy.
- B) Living organisms are totally isolated systems that are not subject to the laws of physics.
- C) Sunlight functions as an ultimate source of energy for most forms of life on Earth.
- D) Living organisms are unique in that they do not require energy for survival.
- E) Organisms are able to function efficiently on heat energy alone.
Answer: C
Diff: 2
Section: 6.1
Skill: Synthesis/Evaluation
13) What is the ultimate source of energy for almost all forms of life on Earth?
- A) Heat energy
- B) Solar energy
- C) Thermal energy
- D) Chemical energy
- E) Nuclear energy
Answer: B
Diff: 1
Section: 6.1
Skill: Knowledge/Comprehension
14) In exergonic chemical reactions
- A) the reactants have more energy than the products.
- B) energy is stored by the reactions.
- C) the reactants have less energy than the products.
- D) the reactants and products possess equal amounts of energy.
Answer: A
Diff: 2
Section: 6.2
Skill: Knowledge/Comprehension
15) When solid sodium hydroxide is added to water, the solution gets hot. This is an example of a(n)
- A) endergonic process.
- B) exergonic process.
- C) enzyme-catalyzed process.
- D) release of activation energy.
- E) conversion of kinetic energy to potential energy.
Answer: B
Diff: 2
Section: 6.2
Skill: Application/Analysis
16) Why is photosynthesis considered an endergonic reaction?
- A) Activation energy is not required.
- B) Photosynthesis does not comply with the physical laws of the universe.
- C) Sugar has less energy than the sun.
- D) Protein catalysts are not needed.
- E) Low-energy reactants are converted to high-energy products.
Answer: E
Diff: 2
Section: 6.2
Skill: Knowledge/Comprehension
17) Activation energy is necessary for all ________ reactions.
- A) exergonic
- B) endergonic
- C) coupled
- D) chemical
Answer: D
Diff: 1
Section: 6.2
Skill: Knowledge/Comprehension
18) When, if ever, do molecules stop moving?
- A) at the freezing point (0°C)
- B) at the boiling point (100°C)
- C) at absolute zero (-273.15°C)
- D) never
Answer: C
Diff: 1
Section: 6.2
Skill: Knowledge/Comprehension
19) An ________ chemical reaction releases energy, whereas an ________ reaction requires an input of energy.
- A) exergonic; endergonic
- B) endergonic; exergonic
- C) enzymatic; endergonic
- D) endergonic; enzymatic
- E) equilibrium; exergonic
Answer: A
Diff: 1
Section: 6.2
Skill: Knowledge/Comprehension
20) In the liver, the polysaccharide glycogen is broken down into glucose monomers. The glucose molecules are then released into the blood when blood sugar levels need to be raised. This process is an example of a(n) ________ reaction.
- A) endergonic
- B) exergonic
- C) kinetic
- D) potential
Answer: B
Diff: 2
Section: 6.2
Skill: Application/Analysis
21) Imagine you are conducting an experiment on a yeast enzyme known as sucrase. This enzyme is used by yeast cells to break down sucrose into glucose and fructose. What type of reaction is this?
- A) Metergonic
- B) Exergonic
- C) Endergonic
- D) Spontaneous
Answer: B
Diff: 2
Section: 6.2
Skill: Application/Analysis
22) Which of the following is the best description of a coupled reaction?
- A) Two reactions that occur simultaneously
- B) A reaction that occurs right after another reaction
- C) Two reactions that occur in the same organelle
- D) Reactions that occur during sexual reproduction
- E) Two reactions that involve one providing energy for the other
Answer: E
Diff: 2
Section: 6.3
Skill: Application/Analysis
23) Why is photosynthesis a coupled reaction?
- A) The exergonic reaction occurs in the plant, and the endergonic reaction occurs in the soil.
- B) The exergonic reaction occurs in the plant, and the endergonic reaction occurs in the sun.
- C) Photosynthesis requires a couple of reactants: carbon dioxide and water.
- D) An exergonic reaction occurs in the sun, and an endergonic reaction occurs in the plant.
- E) Sunlight energy enters a plant and is ultimately lost as heat.
Answer: D
Diff: 2
Section: 6.3
Skill: Application/Analysis
24) The most common energy carrier molecule in living organisms is
- A) ATP.
- B) ADP.
- C) DNA.
- D) glucose.
- E) NADPH.
Answer: A
Diff: 1
Section: 6.3
Skill: Knowledge/Comprehension
25) A “high-energy” bond in an ATP molecule is located between
- A) adenine and ribose.
- B) two phosphate groups.
- C) ribose and the first phosphate group.
- D) adenine and the first phosphate group.
Answer: B
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
26) When a muscle cell demands energy to perform its work of contraction, ATP
- A) manufactures more ATP.
- B) enters a metabolic pathway.
- C) is broken down.
- D) is phosphorylated.
- E) catalyzes the reaction.
Answer: C
Diff: 1
Section: 6.3
Skill: Knowledge/Comprehension
27) Which of the following is NOT a commonly used energy carrier in the cell?
- A) ADP
- B) NADH
- C) Electron carriers
- D) ATP
Answer: A
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
28) When a high-energy bond of ATP is broken, what primarily happens to the released energy?
- A) It is lost as light energy.
- B) It functions as a second messenger.
- C) It polarizes the cell.
- D) It converts inorganic phosphates to energy carrier molecules.
- E) It drives endergonic reactions in the cell.
Answer: E
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
29) Which molecule functions in the short-term storage of energy?
- A) Glycogen
- B) Steroids
- C) Phospholipids
- D) Adenosine triphosphate
- E) Protein
Answer: D
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
30) ATP is an energy carrier. Where is the energy actually located?
- A) Attached to the phosphate group
- B) In the bonds between phosphate groups
- C) Attached to the nucleotide
- D) Inside the phosphate
- E) Between the sugar and the phosphate
Answer: B
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
31) FADH2 is an example of a(n)
- A) protein.
- B) electron carrier.
- C) enzyme.
- D) enzyme-substrate complex.
- E) active site.
Answer: B
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
32) Most reactions in the body occur too slowly to sustain life. This is because
- A) all reactions in the body are endergonic.
- B) many reactions require large inputs of activation energy.
- C) no catalysts are present in body cells.
- D) most biological catalysts are not active at body temperature (37°C).
- E) there is not enough ATP in body cells.
Answer: B
Diff: 2
Section: 6.4
Skill: Application/Analysis
33) Which of the following lowers the activation energy of a biochemical reaction?
- A) Presence of a catalyst
- B) High temperature
- C) Low concentration of reactants
- D) Altering pH to 7
- E) High concentration of products
Answer: A
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
34) All of the following statements pertaining to catalysts are true EXCEPT:
- A) biological catalysts are specific enzymes.
- B) catalysts increase activation energy requirements.
- C) catalysts increase the reaction rate.
- D) catalysts are not permanently altered during reaction.
- E) catalysts can be used over and over again.
Answer: B
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
35) The reactant in an enzyme-catalyzed reaction is the
- A) substrate.
- B) active site.
- C) product.
- D) allosteric inhibitor.
- E) activation energy.
Answer: A
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
36) Enzymes are important because they
- A) are structural proteins that make up bodily tissues.
- B) can enable organisms to evade the laws of thermodynamics.
- C) bind irreversibly to substrates.
- D) allow reactions to occur at body temperature.
- E) increase the body temperature of organisms.
Answer: D
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
37) Place these steps of enzyme catalysis in the correct order:
- The substrate and enzyme change shape.
- The substrate enters the active site.
- The enzyme reverts to its original configuration.
- The product is expelled.
- A) 1, 2, 3, 4
- B) 1, 3, 4, 2
- C) 2, 1, 4, 3
- D) 2, 1, 3, 4
- E) 2, 3, 1, 4
Answer: C
Diff: 2
Section: 6.4
Skill: Application/Analysis
38) Which of these statements regarding enzymes is FALSE?
- A) Enzymes are proteins that function as biological catalysts.
- B) Enzymes are highly specific for the molecules to which they attach.
- C) Enzymes provide energy for the reactions they catalyze.
- D) The activity of enzymes can be regulated by factors in their environment.
- E) An enzyme may be used many times for the same specific reaction.
Answer: C
Diff: 2
Section: 6.4
Skill: Application/Analysis
39) Which of the following functions as a biological catalyst?
- A) Energy carrier molecule
- B) Amino acid
- C) Enzyme
- D) Substrate
- E) Steroid
Answer: C
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
40) Which statement best describes the relationship between an enzyme and a reactant?
- A) The relationship is temporary.
- B) Covalent chemical bonds stabilize the relationship.
- C) The enzyme and the reactant molecule are both permanently changed.
- D) The resultant product and the enzyme are permanently bonded together.
- E) The reactant cannot function without the enzyme.
Answer: A
Diff: 2
Section: 6.4
Skill: Application/Analysis
41) Animals have enzymes that break apart starch molecules but not cellulose, despite the fact that both are made up of glucose subunits. Which enzyme characteristic best explains this?
- A) Enzyme activity is regulated.
- B) Enzymes usually speed up chemical reactions.
- C) Enzymes are not permanently changed by the reactions they promote.
- D) Enzymes are highly specific.
- E) All enzymes are proteins.
Answer: D
Diff: 2
Section: 6.4
Skill: Application/Analysis
42) All of the following are examples of competitive inhibitors EXCEPT:
- A) insecticides.
- B) lead.
- C) penicillin.
- D) ibuprofen.
Answer: D
Diff: 2
Section: 6.5
Skill: Knowledge/Comprehension
43) To say that an enzyme has been denatured means that
- A) an inhibitor has bound the enzyme at the active site.
- B) the enzyme is working at its maximal rate.
- C) the enzyme is working at an optimal temperature.
- D) its three-dimensional structure has changed and the enzyme can no longer function properly.
Answer: D
Diff: 2
Section: 6.5
Skill: Knowledge/Comprehension
44) All of the following are ways in which enzymes are regulated by the cell EXCEPT:
- A) a gene coding for the enzyme may be turned off.
- B) by first synthesizing the enzyme in an inactive form.
- C) by feedback inhibition.
- D) a heavy metal may block the enzymes active site.
Answer: D
Diff: 2
Section: 6.5
Skill: Knowledge/Comprehension
45) The hydrolysis of sucrose to glucose and fructose is a spontaneous reaction. However, if you dissolve sucrose in water and keep the solution overnight at room temperature, there is no detectable conversion to glucose and fructose. Why not?
- A) The reaction is at equilibrium.
- B) The energy of the products is higher than the energy of the reactants.
- C) The activation energy of the reaction decreases.
- D) The reaction is endergonic.
- E) The reaction requires a catalyst.
Answer: E
Diff: 2
Section: 6.4
Skill: Application/Analysis
46) The end product of a biosynthetic pathway often acts to block the initial step in that pathway. This phenomenon is called
- A) allosteric activation.
- B) denaturation.
- C) irreversible inhibition.
- D) feedback inhibition.
- E) substrate activation.
Answer: D
Diff: 2
Section: 6.5
Skill: Knowledge/Comprehension
47) Competitive and noncompetitive enzyme inhibitors differ with respect to
- A) the precise location on the enzyme to which they bind.
- B) their pH.
- C) their binding affinities.
- D) their energies of activation.
Answer: A
Diff: 2
Section: 6.5
Skill: Knowledge/Comprehension
48) Which of the following will bind to the active site of an enzyme?
- A) Substrate only
- B) Competitive inhibitor only
- C) Allosteric inhibitor only
- D) Noncompetitive inhibitor only
- E) Both substrate and competitive inhibitor
Answer: E
Diff: 2
Section: 6.5
Skill: Application/Analysis
49) The optimum reaction rate of a particular enzyme occurs at pH 7.3 at 37°C. This reaction would probably proceed faster by
- A) decreasing the pH and increasing the temperature.
- B) increasing the temperature to 38°C and keeping the pH at 7.3.
- C) increasing the pH and maintaining the temperature at 37°C.
- D) increasing both temperature and pH.
Answer: B
Diff: 2
Section: 6.5
Skill: Application/Analysis
50) For many enzymes, the rate of product formation increases as the concentration of the substrate increases. Eventually the rate of the reaction reaches a maximum at which further increases in the concentration of the substrate have no effect. Why?
- A) At high concentrations of substrate, all of the enzyme molecules are bound to substrate molecules.
- B) At high concentrations of substrate, the activation energy of the reaction increases.
- C) At high concentrations of substrate, the activation energy of the reaction decreases.
- D) The enzyme is no longer specific for the substrate.
- E) At high concentrations of substrate, the reaction is endergonic.
Answer: A
Diff: 3
Section: 6.5
Skill: Synthesis/Evaluation
51) The addition of a competitive inhibitor slows down a particular reaction. What could be done to increase the rate of the reaction, even in the presence of the inhibitor?
- A) Add more inhibitor.
- B) Add more substrate.
- C) Lower the temperature of the reaction.
- D) Add a coenzyme.
- E) Allow the reaction to reach equilibrium.
Answer: B
Diff: 3
Section: 6.5
Skill: Synthesis/Evaluation
52) Sulfa antibiotics damage bacteria by affecting a certain bacterial enzyme. The sulfa antibiotic looks similar to a substrate normally required by the bacterial cells to live. The sulfa antibiotic occupies the active site of the required enzyme and blocks entry of its normal substrate. This prevents the bacteria from making nucleotides that are required for their reproduction and survival. Based on this information, the action of sulfa antibiotics is an example of
- A) electron carriers.
- B) competitive inhibition.
- C) denaturing of proteins.
- D) activation energy.
Answer: B
Diff: 3
Section: 6.5
Skill: Application/Analysis
53) Preservatives such as citric acid are added to foods to interfere with bacterial growth. This creates an acidic pH in the food. Why does this affect the bacteria that are present?
- A) An acidic environment encourages endergonic reactions in the bacterial cells.
- B) An acidic environment increases the activation energy more quickly in bacteria.
- C) An acidic environment causes bacterial enzymes to fail or work less efficiently.
- D) An acidic environment causes the bacteria to grow more rapidly.
Answer: C
Diff: 3
Section: 6.5
Skill: Application/Analysis
54) Triclosan is a broad-spectrum antibacterial agent used in many household products. It is structurally similar to polychlorobiphenylol, a substrate that binds to the active site of the enzyme sulfotransferase. Based on these facts, you can conclude that triclosan most likely:
- A) lowers the activation energy of chemical reactions.
- B) functions as an enzyme when sulfotransferase is absent.
- C) is a competitive inhibitor.
- D) acts as a noncompetitive inhibitor.
Answer: C
Diff: 2
Section: 6.5
Skill: Application/Analysis
6.2 True/False Questions
1) The law of conservation of energy states that although the form of energy used remains the same, the total amount of energy changes. True or False?
Answer: FALSE
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
2) Energy is defined as the capacity to do work. True or False?
Answer: TRUE
Diff: 1
Section: 6.1
Skill: Knowledge/Comprehension
3) Kinetic energy is like sitting at the top of a hill, and potential energy is like coasting down that hill on your bike. True or False?
Answer: FALSE
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
4) The photosynthetic reaction is considered to be an endergonic reaction. True or False?
Answer: TRUE
Diff: 2
Section: 6.2
Skill: Knowledge/Comprehension
5) The burning of sugar is an example of an endergonic reaction, and photosynthesis is an example of an exergonic reaction. True or False?
Answer: FALSE
Diff: 2
Section: 6.2
Skill: Knowledge/Comprehension
6) In cells, endergonic reactions are often coupled with enzymatic reactions that store energy. True or False?
Answer: FALSE
Diff: 2
Section: 6.2
Skill: Knowledge/Comprehension
7) ADP stores energy in its chemical bonds and is able to use that energy for work in the cell. True or False?
Answer: FALSE
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
8) Activation energy can be provided by the kinetic energy of moving molecules. True or False?
Answer: TRUE
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
9) The metabolism of a cell is the sum of all its chemical reactions. True or False?
Answer: TRUE
Diff: 1
Section: 6.5
Skill: Knowledge/Comprehension
6.3 Fill-in-the-Blank Questions
1) The second law of thermodynamics states that the ________, or disorder, of the universe is constantly increasing.
Answer: entropy
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
2) Energy transformations are not 100% efficient. Often, energy is released in the form of ________, which is in agreement with the second law of thermodynamics.
Answer: heat
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
3) The energy of movement is referred to as ________ energy, and stored energy is referred to as ________ energy.
Answer: kinetic; potential
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
4) Sitting at the top of a slide, a child has ________ energy; sliding down, she is using ________ energy.
Answer: potential; kinetic
Diff: 2
Section: 6.1
Skill: Application/Analysis
5) In chemical reactions, the ________ are converted into products.
Answer: reactants
Diff: 1
Section: 6.2
Skill: Knowledge/Comprehension
6) In chemical reactions, ________ reactions release energy and ________ reactions require an input of energy.
Answer: exergonic; endergonic
Diff: 3
Section: 6.2
Skill: Knowledge/Comprehension
7) The burning of sugars as fuels for runners is an example of an ________ chemical reaction, whereas the production of sugars during photosynthesis is an example of an ________ chemical reaction.
Answer: exergonic; endergonic
Diff: 2
Section: 6.2
Skill: Application/Analysis
8) The molecule ________ is the major energy carrier in cells.
Answer: ATP
Diff: 1
Section: 6.3
Skill: Knowledge/Comprehension
9) ATP is considered a short-term form of energy for the cell, whereas ________ represent more stable, long-term energy stores.
Answer: carbohydrates (sucrose, glycogen) or fats
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
10) Special molecules such as NADH and FADH2 transport ________ in cells, which can then be used as energy in the cell.
Answer: electrons
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
11) ________ are biological catalysts.
Answer: Enzymes
Diff: 2
Section: 6.4
Skill: Knowledge/Comprehension
12) The enzyme phosphoglucoisomerase catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate. The region on phosphoglucoisomerase where glucose-6-phosphate binds is called the ________ ________.
Answer: active site
Diff: 2
Section: 6.4
Skill: Application/Analysis
6.4 Short Answer Questions
1) Briefly describe the difference between kinetic energy and potential energy, and give an example of each.
Answer: Kinetic energy is the energy of motion (examples include heat, light, electricity, a car moving), and potential energy is stored energy (examples include energy in chemical bonds, batteries, child sitting at the top of a slide).
Diff: 2
Section: 6.1
Skill: Synthesis/Evaluation
2) Briefly explain the two laws of thermodynamics.
Answer: The law of the conservation of energy states that although the form of energy changes, the total amount remains the same. The second law states that as energy changes from one form to another, the amount of useful energy decreases.
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
3) What is a simple definition of energy, from a biological perspective? Give some examples of how energy is used in a cell.
Answer: Energy is the ability of a cell to do work. The cell uses energy to synthesize molecules, move objects, and generate heat (other examples could be used).
Diff: 2
Section: 6.1
Skill: Knowledge/Comprehension
4) Compare endergonic and exergonic chemical reactions using an analogy from everyday life.
Answer: There are many possible examples: Rolling a boulder up a hill requires an input of energy (an endergonic process), whereas the same boulder, once given a push, rolls down the hill spontaneously (an exergonic process).
Diff: 2
Section: 6.2
Skill: Synthesis/Evaluation
5) Briefly describe how ATP acts as an energy carrier in cells.
Answer: ATP stores energy in its chemical bonds and releases the energy when needed with the breaking of the third phosphate bond (forming ADP and phosphate).
Diff: 2
Section: 6.3
Skill: Knowledge/Comprehension
6) Describe the molecular difference between ATP and ADP.
Answer: Both ATP and ADP contain an adenosine and a sugar. In ATP three phosphate groups are attached, whereas in ADP only two phosphate groups are attached.
Diff: 2
Section: 6.3
Skill: Synthesis/Evaluation
7) Coupled reactions are important components of human physiology. Describe an example of a coupled reaction in the human body.
Answer: A coupled reaction is when an exergonic reaction provides the energy needed to drive an endergonic reaction. One example is when the chemical breakdown of sugars in the human body (exergonic reactions) is used to fuel essential endergonic reactions such as muscle contractions.
Diff: 3
Section: 6.3
Skill: Application/Analysis
8) Explain how enzymes decrease the activation energy required for biological processes in our bodies.
Answer: Enzymes decrease the activation energy by a combination of factors, including substrate orientation, formation of temporary chemical bonds, electrostatic interactions, and bond distortion.
Diff: 2
Section: 6.4
Skill: Application/Analysis
9) Describe the biochemical properties of a biological catalyst.
Answer: Catalysts (enzymes) speed up only those reactions that would occur spontaneously anyway. They are not consumed in the reaction, nor are they permanently changed after the reaction is completed.
Diff: 2
Section: 6.4
Skill: Application/Analysis
10) Why does increasing the temperature of a chemical reaction generally increase the rate of the reaction?
Answer: Increasing the temperature increases the kinetic energy of the reactants, causing the molecules to interact more frequently and with sufficient speed to overcome the activation energy of the reaction.
Diff: 2
Section: 6.5
Skill: Knowledge/Comprehension
11) Normally, a certain enzyme has maximum activity at 37°C, but once it has been heated to 100°C and then cooled back down to 37°C, the enzyme is no longer active. Why?
Answer: The enzyme’s three-dimensional shape has been distorted, and the active site is no longer able to bind the appropriate substrates in the reaction.
Diff: 3
Section: 6.5
Skill: Synthesis/Evaluation
6.5 Art Questions
1) This figure shows the metabolism of glucose and oxygen to CO2 and H2O. From what molecule do the carbon in CO2 and the hydrogen in H2O come from?
- A) Glucose
- B) The product
- C) O2
- D) The catalyst
Answer: A
Diff: 1
Section: 6.4
Skill: Application/Analysis
2) Which of the enzymes shown is active in the stomach of the human digestive tract?
Answer: pepsin
Diff: 1
Section: 6.4
Skill: Knowledge/Comprehension
6.6 Scenario Questions
1) When certain molecules are pumped across biological membranes against a concentration gradient via active transport, ATP is used. In the cells of our bodies, for example, sugars are actively transported and metabolized within the membrane-enclosed mitochondria. Prokaryotes, in contrast, lack mitochondria but are nonetheless able to metabolize the same sugars.
Based on the details provided in this scenario, which of the following statements is expected to be true?
- A) The sugar-digesting enzymes in eukaryotic cells, such as sucrase, are not the same sugar-digesting enzymes found in prokaryotic cells.
- B) Overall, prokaryotes will gain more ATP per sugar molecule metabolized than will eukaryotes.
- C) Prokaryotes and eukaryotes should have the same metabolic efficiency when digesting the same sugars, assuming their enzymes are the same.
- D) Sugar metabolism in prokaryotes is exergonic, whereas in eukaryotes it is endergonic.
Answer: B
Diff: 3
Section: 6.3
Skill: Synthesis/Evaluation
2) Imagine you are conducting an experiment on an enzyme known as sucrase. This enzyme is synthesized and used by yeast cells to break down the disaccharide sucrose (table sugar) into the monosaccharides glucose and fructose. You decide to conduct an experiment to test whether the sucrase enzyme can break down the artificial sweetener sucralose. Sucralose (a “chlorinated” carbohydrate) has some chemical similarity to sucrose, but is different in that three of its hydroxyl groups are missing and replaced with chlorine atoms instead.
Based on the details provided in this scenario, do you think the sucrase enzyme will be able to interact with sucralose?
- A) Yes; enzymes such as sucrase are not specific for their substrate.
- B) No; all enzymes are highly specific and can react with only a specific substrate.
- C) No; sucralose is an ion and not a true carbohydrate.
- D) Yes; the enzymes in human cells can interact with artificial sweeteners as if they were sugars.
Answer: B
Diff: 3
Section: 6.4
Skill: Synthesis/Evaluation
Biology: Life on Earth with Physiology, 10e (Audesirk)
Chapter 7 Capturing Solar Energy: Photosynthesis
7.1 Multiple Choice Questions
1) Before photosynthesis evolved, ________ was rare in Earth’s atmosphere.
- A) N2
- B) CO2
- C) O2
- D) H2O
- E) air
Answer: C
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
2) The products of photosynthesis are
- A) glucose and water.
- B) carbon dioxide, water, and energy.
- C) glucose and carbon dioxide.
- D) carbon dioxide, chlorophyll, and oxygen.
- E) glucose and oxygen.
Answer: E
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
3) What structural feature of a leaf enables it to obtain CO2 from the air?
- A) Stomata
- B) Epidermis
- C) Cuticle
- D) Mesophyll
- E) Chloroplast
Answer: A
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
4) The vast majority of chloroplasts found in a leaf are in the
- A) vascular bundles.
- B) cuticle.
- C) epidermis.
- D) stroma.
- E) mesophyll.
Answer: E
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
5) Specifically, molecules of chlorophyll are located in the membranes of sacs called
- A) stoma.
- B) thylakoids.
- C) stroma.
- D) grana.
- E) vesicles.
Answer: B
Diff: 1
Section: 7.1
Skill: Knowledge/Comprehension
6) All of the following factors influence the rate of photosynthesis EXCEPT:
- A) light intensity.
- B) temperature.
- C) atmospheric CO2
- D) water availability.
- E) atmospheric N2
Answer: E
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
7) All of the following compounds are necessary constituents for photosynthesis EXCEPT:
- A) ATP.
- B) NADP.
- C) water.
- D) oxygen.
- E) carbon dioxide.
Answer: D
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
8) The cellular organelle that utilizes sunlight to convert carbon dioxide and water into sugar and oxygen is the
- A) thylakoid.
- B) mitochondrion.
- C) chloroplast.
- D) endoplasmic reticulum.
- E) cristae.
Answer: C
Diff: 1
Section: 7.1
Skill: Knowledge/Comprehension
9) Imagine that a scientist discovers a mutant plant seedling that appears to lack stomata. What would be the effect of this?
- A) CO2would not be able to enter the plant as a reactant for photosynthesis.
- B) Water would not be able to enter the plant as a reactant for photosynthesis.
- C) Visible wavelengths of light would be unable to reach the chloroplasts.
- D) Additional ATP would be produced by the seedling, and the plant would grow taller.
Answer: A
Diff: 2
Section: 7.1
Skill: Application/Analysis
10) Imagine that a plant in your garden doesn’t receive an adequate amount of water. Which of the following would be most affected by this?
- A) the light reactions of photosynthesis only
- B) the Calvin cycle of photosynthesis only
- C) both the light reactions and the Calvin cycle of photosynthesis
- D) neither the light reactions nor the Calvin cycle of photosynthesis
Answer: C
Diff: 2
Section: 7.1
Skill: Application/Analysis
11) Albino corn has no chlorophyll. You would expect albino corn seedlings to
- A) capture light energy in the white end of the visible light spectrum.
- B) fail to thrive because they cannot capture light energy.
- C) synthesize glucose indefinitely, using stored ATP and NADPH.
- D) switch from the C4pathway to the CAM pathway.
- E) use accessory pigments such as carotenoids to capture light.
Answer: B
Diff: 3
Section: 7.2
Skill: Application/Analysis
12) The energy required for photosynthesis to occur is
- A) glucose.
- B) ultraviolet light.
- C) visible light.
- D) air.
- E) oxygen.
Answer: C
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
13) In the chloroplast, energy in sunlight is passed around different chlorophyll molecules until it reaches a specific chlorophyll molecule that can transfer energy in sunlight to an energized electron. This chlorophyll molecule is called the
- A) reaction center.
- B) photoelectric point.
- C) electron carrier molecule.
- D) accessory pigment.
- E) nucleus.
Answer: A
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
14) Carotenoid pigments are found in the
- A) mitochondria.
- B) stroma of the chloroplasts.
- C) thylakoid membranes of the chloroplasts.
- D) nucleus.
Answer: C
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
15) Pigments that absorb light energy to drive photosynthesis include which of the following?
- A) Chlorophyll only
- B) Carotenoids only
- C) Anthocyanins only
- D) Chlorophyll and carotenoids
- E) Carotenoids and anthocyanins
Answer: D
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
16) A pigment that absorbs red and blue light and reflects green light is
- A) phycocyanin.
- B) carotenoid.
- C) xanthophyll.
- D) melanin.
- E) chlorophyll.
Answer: E
Diff: 1
Section: 7.2
Skill: Knowledge/Comprehension
17) Which of the following is NOT true of chlorophyll?
- A) It reflects green wavelengths of light.
- B) It absorbs light at the red and blue ends of the spectrum.
- C) It is the main photosynthetic pigment in plants.
- D) It is found in mitochondria.
- E) It is found in the membrane of a thylakoid disk.
Answer: D
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
18) Suppose that you are experimenting with different types of lighting for your indoor green plants. Which of the following colors of light will be most effective?
- A) Green
- B) Orange-yellow
- C) Black
- D) Red-green
- E) Red-blue
Answer: E
Diff: 2
Section: 7.2
Skill: Application/Analysis
19) Which statement is true regarding the light reactions?
- A) They rely on energy provided by glucose synthesis.
- B) Oxygen is required.
- C) Without water, the system would shut down.
- D) ATP and NADPH are needed.
- E) Without photosystem I, photosystem II could not occur.
Answer: C
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
20) The replacement electrons for the reaction center of photosystem II come from
- A) photosystem I.
- B) H2
- C) glucose.
- D) O2.
- E) NADPH.
Answer: B
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
21) Which sequence accurately describes the flow of electrons in photosynthesis?
- A) Photosystem I → photosystem II → H2O → NADP
- B) Photosystem II → photosystem I → NADP → H2O
- C) H2O → photosystem II → photosystem I → NADP
- D) Photosystem I → photosystem II → NADP → H2O
- E) H2O → photosystem I → photosystem II → NADP
Answer: C
Diff: 2
Section: 7.2
Skill: Application/Analysis
22) The ATP and NADPH synthesized during the light reactions are
- A) dissolved in the cytoplasm.
- B) transported to the mitochondria.
- C) pumped into a compartment within the thylakoid membrane.
- D) transported into the nucleus.
- E) moved to the stroma.
Answer: E
Diff: 3
Section: 7.2
Skill: Knowledge/Comprehension
23) What is produced in the electron transport system associated with photosystem II?
- A) NADPH
- B) ATP
- C) Glucose
- D) O2
- E) CO2
Answer: B
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
24) Light reactions produce
- A) ATP, NADPH, and O2.
- B) ATP, NADPH, and CO2.
- C) glucose, ATP, and O2.
- D) glucose, ATP, and CO2.
- E) ATP, NADPH, and H2
Answer: A
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
25) Where does the O2 released during photosynthesis come from?
- A) CO2
- B) H2O
- C) ATP
- D) C6H12O6
- E) RuBP
Answer: B
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
26) During the process of photosynthesis, solar energy is converted to
- A) chemical energy.
- B) heat energy.
- C) thermal energy.
- D) mechanical energy.
- E) nuclear energy.
Answer: A
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
27) The light reactions of photosynthesis result in which of the following?
- A) Oxidation of CO2
- B) Reduction of H2O
- C) Synthesis of ATP
- D) Oxidation of chlorophyll
- E) Oxidation of glucose
Answer: C
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
28) The role of water in photosynthesis is to
- A) maintain turgor pressure.
- B) provide electrons.
- C) provide oxygen.
- D) provide H2.
Answer: B
Diff: 2
Section: 7.2
Skill: Application/Analysis
29) Which of the following is a source of electrons that plants use for reduction reactions during photosynthesis?
- A) Glucose
- B) CO2
- C) RuBP
- D) O2
- E) H2O
Answer: E
Diff: 2
Section: 7.2
Skill: Application/Analysis
30) Hydrogen ions cross the thylakoid membranes from the stroma by
- A) osmosis.
- B) facilitated diffusion.
- C) active transport.
- D) simple diffusion.
- E) synthesis.
Answer: C
Diff: 3
Section: 7.2
Skill: Knowledge/Comprehension
31) The energy of the movement of electrons down a concentration gradient via electron transport within chloroplasts and mitochondria is used to generate molecules of
- A) H2
- B) CO2.
- C) glucose.
- D) ATP.
- E) O2.
Answer: D
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
32) The energy of the movement of electrons down a concentration gradient via electron transport within the thylakoid membrane is used to generate
- A) H2
- B) CO2.
- C) glucose.
- D) O2.
- E) ATP.
Answer: E
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
33) Which process of photosynthesis is linked to the production of ATP?
- A) Photosystem II
- B) Generation of NADPH
- C) Splitting of a water molecule
- D) Fixing of carbon
- E) Synthesis of O2
Answer: A
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
34) Suppose you are studying photosynthesis in a research lab. You grow your plants in a chamber with a source of water that has a radioactively labeled oxygen atom. What photosynthetic product will be radioactive?
- A) ATP
- B) Glucose
- C) O2gas
- D) NADPH
- E) CO2gas
Answer: C
Diff: 2
Section: 7.2
Skill: Application/Analysis
35) Which of the following statements is true about the light reactions?
- A) NADPH and ATP are both synthesized from the light reactions within photosystem I.
- B) Photosystem I generates ATP, whereas photosystem II generates NADPH.
- C) Photosystem II generates ATP, whereas photosystem I generates NADPH.
- D) ATP is the final electron acceptor.
Answer: C
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
36) Which of the following statements about the light reactions of photosynthesis is FALSE?
- A) The splitting of water molecules provides a source of electrons.
- B) Chlorophyll (and other pigments) absorbs light energy, which excites electrons.
- C) An electron transport chain is used to create a proton gradient.
- D) NADPH becomes oxidized to NADP+.
- E) ATP is formed.
Answer: D
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
37) The NADPH required for carbon dioxide fixation during the Calvin cycle is formed
- A) by the reduction of oxygen.
- B) by the hydrolysis of ATP.
- C) during the light reactions.
- D) only in C4
- E) in the mitochondria.
Answer: C
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
38) The primary function of the light reactions of photosynthesis is to
- A) produce energy-rich glucose from carbon dioxide and water.
- B) produce energy-rich ATP and NADPH.
- C) produce NADPH used in respiration.
- D) convert light energy to the chemical energy of lipids.
- E) use ATP to make glucose.
Answer: B
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
39) You are carrying out an experiment on several aquatic plants in your fish tank. You decide to expose two of the plants to green light and two to blue light. You want to determine which type of light is best for the light reactions, so you decide to record the amount of oxygen bubbles produced to reach your conclusions. Which of the following results would be expected?
- A) There would be more bubbles from the plants in green light than from those in blue light.
- B) There would be more bubbles from the plants in blue light than from those in green light.
- C) There would be the same number of bubbles from plants in blue or green light.
- D) No bubbles would be produced in either green light or blue light.
Answer: B
Diff: 3
Section: 7.2
Skill: Application/Analysis
40) Which of the following provides O2 as an end product?
- A) Light reaction
- B) Light-independent reaction
- C) Cellular respiration
- D) Glycolysis
- E) Synthesis
Answer: A
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
41) Glucose synthesis during photosynthesis requires that
- A) NADH and FADH are available.
- B) the products of light-dependent reactions must be available.
- C) the concentration of O2must be significantly higher than that of CO2.
- D) mitochondria must convert light energy to ATP.
Answer: B
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
42) The term “cycle” is used to describe the Calvin cycle because
- A) the reactions occur only once in a 24-hour day.
- B) CO2is fixed.
- C) the metabolic pathway begins and ends with RuBP.
- D) glucose is synthesized during the process.
- E) the process depends on products from the light reactions.
Answer: C
Diff: 2
Section: 7.3
Skill: Application/Analysis
43) Where is glucose synthesized during photosynthesis?
- A) Thylakoids
- B) Cytoplasm
- C) Matrix
- D) Stroma
- E) Membrane proteins
Answer: D
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
44) What is the correct order for the reactions of the Calvin cycle?
- A) Carbon fixation, regeneration of RuBP, synthesis of G3P
- B) Synthesis of G3P, regeneration of RuBP, carbon fixation
- C) Carbon fixation, synthesis of G3P, regeneration of RuBP
- D) Regeneration of RuBP, carbon fixation, synthesis of G3P
- E) Synthesis of G3P, carbon fixation, regeneration of RuBP
Answer: C
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
45) Which of the following occurs during the Calvin cycle of photosynthesis?
- A) Water is converted to its most basic elements, hydrogen and water.
- B) Carbon dioxide is converted to chemicals that can be used to make sugars.
- C) Chlorophyll acts as an enzyme, but only in the dark.
- D) Nothing occurs because the plant rests in the dark.
Answer: B
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
46) All of the following are part of the Calvin cycle EXCEPT:
- A) carbon fixation.
- B) synthesis of G3P.
- C) generation of ATP.
- D) regeneration of RuBP.
Answer: C
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
47) What happens to CO2 when it moves into the stroma?
- A) The CO2gives up its O2.
- B) It immediately passes on to the thylakoids.
- C) It gets incorporated into the Calvin cycle and becomes a carbohydrate.
- D) The CO2becomes a by-product of cellular respiration.
- E) It is converted to water.
Answer: C
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
48) In green plants, the primary function of the Calvin cycle is to
- A) use ATP to release carbon dioxide.
- B) use NADPH to release carbon dioxide.
- C) split water and release oxygen.
- D) transport glucose out of the chloroplast.
- E) construct the building blocks of simple sugars from carbon dioxide.
Answer: E
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
49) Glucose is made during which of the following reactions?
- A) The light reactions only
- B) The Calvin cycle only
- C) Both the light reactions and the Calvin cycle
- D) Neither the light reactions nor the Calvin cycle
Answer: B
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
50) During photosynthesis, when is CO2 utilized?
- A) During the light reactions only
- B) During the Calvin cycle only
- C) During both the light reactions and the Calvin cycle
- D) During neither the light reactions nor the Calvin cycle
Answer: B
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
51) NADPH is required during which of the following reactions?
- A) The light reactions only
- B) The Calvin cycle only
- C) Both the light reactions and the Calvin cycle
- D) Neither the light reactions nor the Calvin cycle
Answer: B
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
52) Enzymes are required during which of the following reactions?
- A) The light reactions only
- B) The Calvin cycle only
- C) Both the light reactions and the Calvin cycle
- D) Neither the light reactions nor the Calvin cycle
Answer: C
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
53) Water is required to drive which of the following reactions?
- A) The light reactions only
- B) The Calvin cycle only
- C) Both the light reactions and the Calvin cycle
- D) Neither the light reactions nor the Calvin cycle
Answer: A
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
54) NADPH is synthesized during which of the following reactions?
- A) The light reactions only
- B) The Calvin cycle only
- C) Both the light reactions and the Calvin cycle
- D) Neither the light reactions nor the Calvin cycle
Answer: A
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
55) In the C3 pathway, where does the carbon come from to form glucose?
- A) ATP and NADPH
- B) Chlorophyll
- C) Atmospheric CO2
- D) Enzymes
- E) Water
Answer: C
Diff: 2
Section: 7.3
Skill: Knowledge/Comprehension
56) In the reduction of CO2 during C4 photosynthesis, which of the following initially combines with CO2?
- A) PGA
- B) RuBP
- C) PGAL
- D) NADH
- E) PEP
Answer: E
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
57) Where do the reactions of a C4 pathway occur in a plant such as corn?
- A) Mesophyll cells only
- B) Bundle sheath cells only
- C) Epidermal cells only
- D) Mesophyll and bundle sheath cells
- E) Bundle sheath and epidermal cells
Answer: D
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
58) In the C4 pathway, what is the source of carbon?
- A) NADPH
- B) Glucose
- C) Water
- D) Carbon dioxide
- E) ATP
Answer: D
Diff: 2
Section: 7.4
Skill: Application/Analysis
59) What kind of habitat does a C4-pathway plant favor?
- A) Hot and dry
- B) Cool and moist
- C) Totally aquatic
- D) Wet and cloudy
- E) Cool and dry
Answer: A
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
60) Photorespiration is detrimental for a plant because
- A) O2is required.
- B) CO2is synthesized.
- C) RuBP is degraded.
- D) glucose is synthesized.
- E) no glucose is produced.
Answer: E
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
61) Where does the C4 cycle get its name?
- A) Only four carbons are used in the cycle.
- B) It is a four-step process.
- C) Four CO2molecules are released.
- D) The first product in the cycle has four carbons.
- E) PEP is a four-carbon molecule.
Answer: D
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
62) If C4 photosynthesis prevents photorespiration, why haven’t all plants evolved to use the C4 pathway?
- A) All plants will evolve to be C4in time.
- B) C4produces some toxic by-products.
- C) C4is not advantageous in all climates.
- D) Only some plants use C4
- E) C4is advantageous in only high-oxygen habitats.
Answer: C
Diff: 2
Section: 7.4
Skill: Synthesis/Evaluation
63) C3 plants are adapted to ________ environmental conditions, whereas C4 plants are adapted to ________ conditions.
- A) dry; wet
- B) wet; dry
- C) temperate; cool and rainy
- D) high-light; low-light
- E) drought; rainy
Answer: B
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
64) In C3 photosynthesis, what fixes the carbon?
- A) RuBP
- B) PEP
- C) PGA
- D) PGAL
- E) ATP
Answer: A
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
65) In C4 photosynthesis, where does the carbon in newly synthesized glucose come from?
- A) ATP and NADPH
- B) Chlorophyll
- C) Enzymes
- D) Water
- E) Atmospheric CO2
Answer: E
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
66) All of the following are true of biofuels EXCEPT:
- A) The goal of their use is to reduce harmful carbon dioxide emissions.
- B) These are fuels such as methane produced from renewable biological resources such as soybeans and corn.
- C) There is concern that using food products as a fuel sources will reduce the global food supply and increase food prices.
- D) Demand for biofuels has placed demands on rain forest lands.
- E) Biofuels are the only solution to our growing need for fuels in the future.
Answer: E
Diff: 2
Section: 7.3
Skill: Application/Analysis
7.2 True/False Questions
1) The stacked thylakoids are disk-shaped, interconnected membranous sacs embedded in the membrane of the stroma. True or False?
Answer: FALSE
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
2) The majority of the leaf’s chloroplasts are found in the mesophyll cells. True or False?
Answer: TRUE
Diff: 1
Section: 7.1
Skill: Knowledge/Comprehension
3) The photosystems are involved in the light reactions of photosynthesis. True or False?
Answer: TRUE
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
4) Carbon dioxide is required in the light reactions of photosynthesis. True or False?
Answer: FALSE
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
5) The carotenoids and other accessory pigments in the chloroplast help capture light into the reaction center’s chlorophyll molecules. True or False?
Answer: TRUE
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
6) Under dry conditions, a C4 plant is more efficient at photosynthesis than a C3 plant. True or False?
Answer: TRUE
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
7.3 Fill-in-the-Blank Questions
1) Light reactions occur in the ________, and the Calvin cycle occurs in the ________ of the chloroplast of a typical mesophyll leaf cell.
Answer: thylakoids; stroma
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
2) The cells in the ________ layer of the leaf contain the majority of a leaf’s chloroplasts.
Answer: mesophyll
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
3) The process of photosynthesis converts solar energy to ________ energy stored in the bonds of glucose.
Answer: chemical
Diff: 1
Section: 7.1
Skill: Knowledge/Comprehension
4) Many plants have evolved leaves that have adjustable pores, called ________, which allow for gas exchange and water loss.
Answer: stomata
Diff: 2
Section: 7.1
Skill: Knowledge/Comprehension
5) ________ is the main light-capturing molecule in chloroplasts and is responsible for giving leaves their characteristic green color.
Answer: Chlorophyll
Diff: 1
Section: 7.2
Skill: Knowledge/Comprehension
6) In the process of photosynthesis, ________ and ________ formed during the light reactions are required in the Calvin cycle to reduce carbon dioxide to glucose.
Answer: ATP; NADPH
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
7) During the light reactions of photosynthesis, the synthesis of ________ is coupled to the diffusion of protons.
Answer: ATP
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
8) Light-harvesting pigments in the chloroplast include chlorophyll and the yellowish accessory pigments called ________.
Answer: carotenoids
Diff: 1
Section: 7.2
Skill: Knowledge/Comprehension
9) A(n) ________ is composed of a light-harvesting complex of chlorophyll pigments and an electron transport system.
Answer: photosystem
Diff: 1
Section: 7.2
Skill: Knowledge/Comprehension
10) Photosystem II generates ________, and photosystem I generates ________, both of which are required by the light reactions.
Answer: ATP; NADPH
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
11) During the Calvin cycle, the combination of oxygen with RuBP rather than carbon dioxide is called ________.
Answer: photorespiration
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
12) Some plants, called the ________ plants, have evolved a way to reduce photorespiration.
Answer: C4
Diff: 1
Section: 7.4
Skill: Knowledge/Comprehension
13) During the process of ________, RuBP combines with oxygen instead of carbon dioxide.
Answer: photorespiration
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
14) In C3 plants, the Calvin cycle occurs in the chloroplasts of ________ cells, but in C4 plants, the Calvin cycle occurs in the ________ cells.
Answer: mesophyll; bundle sheath
Diff: 2
Section: 7.4
Skill: Knowledge/Comprehension
7.4 Short Answer Questions
1) Give the simplest chemical equation for photosynthesis. For each reactant, indicate where the plant acquires it. For each product, note during what part of photosynthesis it is produced.
Answer: The chemical equation for photosynthesis is
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
CO2 comes through the stomata, water comes from the vascular bundles (or veins) to the mesophyll cells, and chlorophyll molecules embedded in the thylakoid membrane of the chloroplast absorb sunlight. The glucose is produced immediately following the Calvin cycle, and the oxygen is produced during the light reactions.
Diff: 3
Section: 7.1
Skill: Synthesis/Evaluation
2) Explain how the leaf is adapted for capturing energy from sunlight and for acquiring carbon dioxide and water.
Answer: CO2 comes through adjustable pores, or stomata, and water comes from the vascular bundles (or veins) to the mesophyll cells. Leaves are broad and flat to provide a large surface area to the sun. Chlorophyll molecules embedded in the thylakoid membrane of the chloroplast absorb sunlight.
Diff: 2
Section: 7.1
Skill: Application/Analysis
3) What is the role of the green pigment chlorophyll in photosynthesis?
Answer: Chlorophyll is critical in light reactions to harness light energy and begin the flow of electrons, which in turn creates the proton gradient allowing for ATP formation, which is required for the Calvin cycle.
Diff: 2
Section: 7.2
Skill: Application/Analysis
4) Describe the two major components of a photosystem. What is the function of each?
Answer: The light-harvesting complex absorbs light and passes the energy to a specific chlorophyll molecule called the reaction center. The electron transport system is a series of electron carrier molecules that are responsible for directly donating electrons to the electron carrier molecule NADP+ and indirectly driving the synthesis of ATP.
Diff: 2
Section: 7.2
Skill: Knowledge/Comprehension
5) Imagine you are conducting a photosynthesis experiment on a plant in the lab. You block any light from reaching the plant. Explain the specific effect this will have on the light reactions.
Answer: Light will not be present to hit the chlorophyll and electrons will not be excited. Therefore, the light reactions will not occur and no energy will be produced to be used in the dark reactions.
Diff: 1
Section: 7.2
Skill: Application/Analysis
6) Is glucose a direct product of the Calvin cycle?
Answer: No; G3P is the carbohydrate produced, and two of these molecules must combine to form one molecule of glucose.
Diff: 2
Section: 7.3
Skill: Application/Analysis
7) Which component of the Calvin cycle is recycled, and why is this important for the Calvin cycle?
Answer: The RuBP molecule is recycled. This is essential to maintain the cyclical nature of the process.
Diff: 2
Section: 7.3
Skill: Application/Analysis
8) How are the light reactions and the Calvin cycle related to each other?
Answer: The light reactions produce the ATP and NADPH required to drive the Calvin cycle, which results in the synthesis of sugar (glucose).
Diff: 2
Section: 7.3
Skill: Synthesis/Evaluation
9) What happens to the photosynthetic reactions when no sunlight is present?
Answer: ATP and NADPH levels from the light reactions become limiting, and that in turn can lead to a decrease in sugar production following the Calvin cycle.
Diff: 2
Section: 7.3
Skill: Application/Analysis
10) Why does photorespiration reduce photosynthesis efficiency?
Answer: Photorespiration does not produce any useful cellular energy, and it prevents the synthesis of glucose in C3 plants.
Diff: 2
Section: 7.4
Skill: Application/Analysis
11) What is photorespiration? Describe how C4 plants have evolved the ability to reduce photorespiration.
Answer: Photorespiration occurs when RuBP combines with O2 rather than CO2, so the plant is not allowed to fix carbon and produce glucose. C4 plants use a two-stage carbon-fixation pathway where PEP is used instead of RuBP, which specifically reacts with CO2 and not O2. The CO2 is then shuttled to the bundle sheath cells and creates a high CO2 concentration that favors the regular C3 cycle reactions without competition from O2.
Diff: 3
Section: 7.4
Skill: Application/Analysis
7.5 Art Questions
1) Based on the information provided in this figure, where does the oxygen gas produced by a leaf come from?
- A) C6H12O6
- B) CO2
- C) H2O
- D) NADPH
Answer: C
Diff: 1
Section: 7.1
Skill: Knowledge/Comprehension
2) Based on this graph, which wavelengths of light would result in the highest rates of ATP production during photosynthesis?
- A) 450-500 nanometers
- B) 550-600 nanometers
- C) 600-650 nanometers
- D) 700-750 nanometers
Answer: A
Diff: 1
Section: 7.2
Skill: Synthesis/Evaluation
3) Based on the information provided in this figure, what event contributes directly to the creation of a proton gradient across the thylakoid membrane?
- A) The creation of C6H12O6
- B) The flow of electrons through photosystem I
- C) The splitting of H2O
- D) The creation of ATP
- E) The flow of electrons through electron transport chain II
Answer: E
Diff: 1
Section: 7.2
Skill: Application/Analysis
7.6 Scenario Questions
1) Imagine that, similar to events that occurred 65 million years ago, a huge meteorite were to hit Earth tomorrow, spewing cloudy debris into the atmosphere and blocking a large proportion of sunlight. Because plants rely on sunlight, global rates of photosynthesis would be greatly reduced, and many of the animals that depend on photosynthetic plants (such as herbivores and the predators that feed on those herbivores) would starve or go extinct.
In this scenario, why can’t the plants continue to produce sugars and survive if the sugar-producing reactions in photosynthesis are considered “light independent”?
Answer: The Calvin cycle, used to drive the synthesis of glucose, requires ATP and NADPH produced from the light reactions.
Diff: 2
Section: 7.3
Skill: Synthesis/Evaluation
2) Consider the scenario of two scientists conducting an experiment to track what happens to the carbon atoms from CO2 molecules used during the Calvin cycle of photosynthesis. They add a radioactive “tag” to the carbon atoms of the CO2 reactants and then collect the products following the reactions. They analyze the products for their level of radioactivity.
Which product(s) would you expect to be radioactive?
- A) ATP only
- B) Water only
- C) Glucose only
- D) Both water and glucose
- E) Both ATP and water
Answer: C
Diff: 3
Section: 7.3
Skill: Application/Analysis
