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Biology I - Exam 3

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Quiz on Biology I - Exam 3, created by acbridges91 on 10/05/2015.
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Quiz by acbridges91, updated more than 1 year ago
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Question 1

Question
Which of the following is true of metabolism in its entirety in all organisms?
Answer
  • Metabolism uses all of an organism's resources.
  • Metabolism manages the increase of entropy in an organism.
  • Metabolism consists of all the energy transformation reactions in an organism.
  • Metabolism depends on a constant supply of energy from food.

Question 2

Question
Which of the following is an example of potential rather than kinetic energy?
Answer
  • water rushing over Niagara Falls
  • a molecule of glucose
  • a crawling beetle foraging for food
  • light flashes emitted by a firefly

Question 3

Question
Most cells cannot harness heat to perform work because _____.
Answer
  • heat is not a form of energy
  • heat must remain constant during work
  • heat can never be used to do work
  • temperature is usually uniform throughout a cell

Question 4

Question
Which of the following involves a decrease in entropy?
Answer
  • reactions that separate monomers
  • hydrolysis reactions
  • depolymerization reactions
  • condensation reactions

Question 5

Question
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
Answer
  • catabolism (catabolic pathways)
  • dehydration
  • metabolism
  • anabolism (anabolic pathways)

Question 6

Question
Anabolic pathways _____.
Answer
  • are usually highly spontaneous chemical reactions
  • release energy as they degrade polymers to monomers
  • consume energy to build up polymers from monomers
  • consume energy to decrease the entropy of the organism and its environment

Question 7

Question
Which of the following is a statement of the first law of thermodynamics?
Answer
  • The entropy of the universe is constant.
  • The entropy of the universe is decreasing.
  • Energy cannot be transferred or transformed.
  • Energy cannot be created or destroyed.

Question 8

Question
For living organisms, which of the following is an important consequence of the first law of thermodynamics?
Answer
  • The organism ultimately must obtain all of the necessary energy for life from its environment.
  • The entropy of an organism decreases with time as the organism grows in complexity.
  • The energy content of an organism is constant.
  • Organisms grow by converting energy into organic matter.

Question 9

Question
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
Answer
  • As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
  • Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe.
  • Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.
  • Living organisms are able to transform energy into entropy.

Question 10

Question
Which of the following statements is representative of the second law of thermodynamics?
Answer
  • Cells require a constant input of energy to maintain their high level of organization.
  • Conversion of energy from one form to another is always accompanied by some gain of free energy.
  • Every energy transformation by a cell decreases the entropy of the universe.
  • Without an input of energy, organisms would tend toward decreasing entropy.

Question 11

Question
Which of the following types of reactions would decrease the entropy within a cell?
Answer
  • digestion
  • hydrolysis
  • catabolic reactions
  • anabolic reactions

Question 12

Question
Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellular eukaryotic organisms, _____.
Answer
  • has been made possible by expending Earth's energy resources
  • has caused an increase in the entropy of the planet
  • has occurred in accordance with the laws of thermodynamics
  • has occurred in accordance with the laws of thermodynamics, by expending Earth's energy resources and causing an increase in the entropy of the planet

Question 13

Question
A system at chemical equilibrium _____.
Answer
  • has zero kinetic energy
  • releases energy at a steady rate
  • can do no work
  • consumes energy at a steady rate

Question 14

Question
Which of the following is true for all exergonic reactions?
Answer
  • The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants.
  • The products have more total energy than the reactants.
  • The reaction proceeds with a net release of free energy.
  • A net input of energy from the surroundings is required for the reactions to proceed.

Question 15

Question
A chemical reaction that has a positive ΔG is best described as _____.
Answer
  • enthalpic
  • spontaneous
  • endergonic
  • exergonic

Question 16

Question
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _____ is to _____.
Answer
  • work; energy
  • exergonic; endergonic
  • free energy; entropy
  • exergonic; spontaneous

Question 17

Question
Why is ATP an important molecule in metabolism?
Answer
  • It provides energy coupling between exergonic and endergonic reactions.
  • Its terminal phosphate bond has higher energy than the other two phosphate bonds.
  • Its hydrolysis provides an input of free energy for exergonic reactions.
  • Its terminal phosphate group contains a strong covalent bond that, when hydrolyzed, releases free energy.

Question 18

Question
Which of the following is most similar in structure to ATP?
Answer
  • a DNA nucleotide
  • a pentose sugar
  • an amino acid with three phosphate groups attached
  • an RNA nucleotide

Question 19

Question
Catabolic pathways _____.
Answer
  • are endergonic
  • are spontaneous and do not need enzyme catalysis
  • combine molecules into more energy-rich molecules
  • supply energy, primarily in the form of ATP, for the cell's work

Question 20

Question
When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?
Answer
  • It is secreted as waste.
  • It may be used to form a phosphorylated intermediate.
  • It is used only to regenerate more ATP.
  • It enters the nucleus and affects gene expression.

Question 21

Question
Which of the following is true of enzymes?
Answer
  • Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.
  • Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.
  • Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
  • Enzyme function is increased if the 3- D structure or conformation of an enzyme is altered.

Question 22

Question
The lock-and-key analogy for enzymes applies to the specificity of enzymes _____.
Answer
  • interacting with water
  • binding to their substrate
  • interacting with ions
  • as they form their tertiary and quaternary structure

Question 23

Question
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's _____.
Answer
  • free-energy content
  • entropy
  • activation energy
  • equilibrium point

Question 24

Question
The active site of an enzyme is the region that _____.
Answer
  • binds allosteric regulators of the enzyme
  • is involved in the catalytic reaction of the enzyme
  • is inhibited by the presence of a coenzyme or a cofactor
  • binds noncompetitive inhibitors of the enzyme

Question 25

Question
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
Answer
  • allosteric inhibition
  • the need for a coenzyme
  • insufficient cofactors
  • competitive inhibition

Question 26

Question
A noncompetitive inhibitor decreases the rate of an enzyme reaction by _____.
Answer
  • binding at the active site of the enzyme
  • acting as a coenzyme for the reaction
  • changing the shape of the enzyme's active site
  • changing the free energy change of the reaction

Question 27

Question
How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity?
Answer
  • by changing the shape of an enzyme
  • by changing the enzyme's stability
  • by changing the enzyme's pH optimum
  • An amino acid change away from the active site cannot alter the enzyme's substrate specificity.

Question 28

Question
HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon?
Answer
  • denaturation
  • allosteric regulation
  • competitive inhibition
  • vaccination

Question 29

Question
Use the following information to answer the questions below. A series of enzymes catalyze the reaction X → Y Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What is substance X?
Answer
  • the product
  • an allosteric inhibitor
  • an intermediate
  • a substrate

Question 30

Question
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as _____.
Answer
  • feedback inhibition
  • noncooperative inhibition
  • allosteric inhibition
  • metabolic inhibition

Question 31

Question
Allosteric enzyme regulation is usually associated with _____.
Answer
  • the need for cofactors
  • feedback inhibition
  • an enzyme with more than one subunit
  • activating activity

Question 32

Question
Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
Answer
  • hydrophobic interactions
  • connecting enzymes into large aggregates
  • localization of enzymes into specific organelles or membranes
  • exporting enzymes out of the cell

Question 33

Question
Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization?
Answer
  • Membrane localization lowers the activation energy of the phosphorylation reaction.
  • ATP is more abundant near the plasma membrane.
  • They can more readily encounter and phosphorylate other membrane proteins.
  • They flip back and forth across the membrane to access target proteins on either side.

Question 34

Question
Substrate-level phosphorylation occurs _____.
Answer
  • in the citric acid cycle
  • in both glycolysis and the citric acid cycle
  • in glycolysis
  • during oxidative phosphorylation

Question 35

Question
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction _____.
Answer
  • gains electrons and loses potential energy
  • loses electrons and gains potential energy
  • loses electrons and loses potential energy
  • gains electrons and gains potential energy

Question 36

Question
When electrons move closer to a more electronegative atom, what happens? The more electronegative atom is _____.
Answer
  • reduced, and energy is consumed
  • reduced, and energy is released
  • oxidized, and energy is consumed
  • oxidized, and energy is released

Question 37

Question
Which of the listed statements describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
Answer
  • O2 is reduced and CO2 is oxidized.
  • C6H12O6 is oxidized and O2 is reduced.
  • O2 is oxidized and H2O is reduced.
  • CO2 is reduced and O2 is oxidized.

Question 38

Question
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes _____.
Answer
  • an oxidizing agent
  • hydrolyzed
  • reduced
  • oxidized

Question 39

Question
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____.
Answer
  • reduced
  • redoxed
  • dehydrogenated
  • oxidized

Question 40

Question
Which of the following statements about NAD+ is true?
Answer
  • NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
  • NAD+ can donate electrons for use in oxidative phosphorylation.
  • NAD+ has more chemical energy than NADH.
  • In the absence of NAD+, glycolysis can still function.

Question 41

Question
The oxygen consumed during cellular respiration is involved directly in which process or event?
Answer
  • glycolysis
  • the oxidation of pyruvate to acetyl CoA
  • the citric acid cycle
  • accepting electrons at the end of the electron transport chain

Question 42

Question
Carbohydrates and fats are considered high-energy foods because they _____.
Answer
  • have a lot of oxygen atoms.
  • are easily reduced.
  • have a lot of electrons associated with hydrogen.
  • have no nitrogen in their makeup.

Question 43

Question
A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
Answer
  • He or she has to sit down and rest.
  • Other cells take over, and the muscle cells that have used up their ATP cease to function.
  • ATP is transported into the cell from the circulatory system.
  • Catabolic processes are activated that generate more ATP.

Question 44

Question
Starting with one molecule of glucose, the energy-containing products of glycolysis are _____.
Answer
  • 6 CO2, 2 pyruvate, and 2 ATP
  • 2 FADH2, 2 pyruvate, and 4 ATP
  • 2 NADH, 2 pyruvate, and 2 ATP
  • 2 NAD+, 2 pyruvate, and 2 ATP

Question 45

Question
In glycolysis, for each molecule of glucose oxidized to pyruvate _____.
Answer
  • four molecules of ATP are used and two molecules of ATP are produced.
  • two molecules of ATP are used and six molecules of ATP are produced.
  • two molecules of ATP are used and four molecules of ATP are produced.
  • two molecules of ATP are used and two molecules of ATP are produced.

Question 46

Question
Most of the CO2 from the catabolism of glucose is released during _____.
Answer
  • glycolysis
  • chemiosmosis
  • the citric acid cycle
  • electron transport

Question 47

Question
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of _____.
Answer
  • NADH
  • acetyl-CoA
  • pyruvate
  • glucose

Question 48

Question
Which electron carrier(s) function in the citric acid cycle?
Answer
  • ADP and ATP
  • NAD+ only
  • the electron transport chain
  • NADH and FADH2

Question 49

Question
Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
Answer
  • acetyl CoA
  • glyceraldehyde 3-phosphate
  • citrate
  • oxaloacetate

Question 50

Question
Which of the following events takes place in the electron transport chain?
Answer
  • substrate-level phosphorylation
  • the extraction of energy from high-energy electrons remaining from glycolysis and the citric acid cycle
  • the breakdown of glucose into two pyruvate molecules
  • the breakdown of an acetyl group to carbon dioxide

Question 51

Question
The electron transport chain _____.
Answer
  • is a series of substitution reactions
  • takes place in the cytoplasm of prokaryotic cells
  • is driven by ATP consumption
  • is a series of redox reactions

Question 52

Question
The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because it explains _____.
Answer
  • the reduction of oxygen to water in the final steps of oxidative metabolism
  • the sequence of the electron transport chain molecules
  • how electron transport can fuel substrate-level phosphorylation
  • how ATP is synthesized by a proton motive force

Question 53

Question
During aerobic respiration, electrons travel downhill in which sequence?
Answer
  • glucose → pyruvate → ATP → oxygen
  • food → glycolysis → citric acid cycle → NADH → ATP
  • glucose → NADH → electron transport chain oxygen
  • glucose → ATP → electron transport chain NADH

Question 54

Question
Where are the proteins of the electron transport chain located?
Answer
  • mitochondrial matrix
  • mitochondrial outer membrane
  • mitochondrial inner membrane
  • mitochondrial intermembrane space

Question 55

Question
During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?
Answer
  • ADP + Pi
  • NADH
  • ATP
  • FADH2

Question 56

Question
The primary role of oxygen in cellular respiration is to _____.
Answer
  • yield energy in the form of ATP as it is passed down the respiratory chain
  • combine with carbon, forming CO2
  • combine with lactate, forming pyruvate
  • act as an acceptor for electrons and hydrogen, forming water

Question 57

Question
During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?
Answer
  • molecular oxygen (O2)
  • carbon dioxide (CO2)
  • pyruvate (C3H3O3-)
  • glucose (C6H12O6)

Question 58

Question
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
Answer
  • mitochondrial matrix
  • mitochondrial inner membrane
  • mitochondrial outer membrane
  • mitochondrial intermembrane space

Question 59

Question
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the _____.
Answer
  • reduction of NAD+
  • creation of a proton-motive force
  • lowering of pH in the mitochondrial matrix
  • formation of ATP

Question 60

Question
Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?
Answer
  • 2
  • 4
  • 30-32
  • 18-24

Question 61

Question
The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of _____.
Answer
  • a reaction with a positive ΔG
  • an endergonic reaction coupled to an exergonic reaction
  • allosteric regulation
  • active transport

Question 62

Question
In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
Answer
  • It allows for an increased rate of the citric acid cycle.
  • It allows for an increased rate of glycolysis.
  • It increases the surface for substrate-level phosphorylation.
  • It increases the surface for oxidative phosphorylation.

Question 63

Question
Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in _____.
Answer
  • all cells, but only in the presence of oxygen
  • only eukaryotic cells, in the presence of oxygen
  • all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors
  • only in mitochondria, using either oxygen or other electron acceptors

Question 64

Question
Which of the following normally occurs regardless of whether or not oxygen (O2) is present?
Answer
  • oxidative phosphorylation (chemiosmosis)
  • citric acid cycle
  • fermentation
  • glycolysis

Question 65

Question
Which of the following occurs in the cytosol of a eukaryotic cell?
Answer
  • glycolysis and fermentation
  • citric acid cycle
  • fermentation and chemiosmosis
  • oxidation of pyruvate to acetyl CoA

Question 66

Question
The process of photosynthesis probably originated _____.
Answer
  • three separate times during evolution
  • in plants
  • in prokaryotes
  • in fungi

Question 67

Question
Plants photosynthesize _____.
Answer
  • only in the light but respire only in the dark
  • only in the dark but respire only in the light
  • only in the light but respire in light and dark
  • and respire only in the light

Question 68

Question
Every ecosystem must have _____.
Answer
  • autotrophs and heterotrophs
  • photosynthesizers
  • producers and primary consumers
  • autotrophs

Question 69

Question
When oxygen is released as a result of photosynthesis, it is a direct by-product of _____.
Answer
  • chemiosmosis
  • the electron transfer system of photosystem II
  • the electron transfer system of photosystem I
  • splitting water molecules

Question 70

Question
Which of the following statements is a correct distinction between autotrophs and heterotrophs?
Answer
  • Cellular respiration is unique to heterotrophs.
  • Only heterotrophs have mitochondria.
  • Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.
  • Only heterotrophs require oxygen.

Question 71

Question
A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed. What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?
Answer
  • green light
  • a mixture of blue and red light
  • full-spectrum white light
  • UV light

Question 72

Question
Why are there several structurally different pigments in the reaction centers of photosystems?
Answer
  • This arrangement enables the plant to absorb light energy of a variety of wavelengths.
  • They enable the reaction center to excite electrons to a higher energy level.
  • They enable the plant to absorb more photons from light energy, all of which are at the same wavelength.
  • Excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain.

Question 73

Question
If pigments from a particular species of plant are extracted and subjected to paper chromatography, which of the following is most likely?
Answer
  • Paper chromatography would isolate only the pigments that reflect green light.
  • Paper chromatography for the plant would isolate a single band of pigment that is characteristic of that particular plant.
  • The isolated pigments would be some shade of green.
  • Paper chromatography would separate the pigments from a particular plant into several bands.

Question 74

Question
In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and _____.
Answer
  • the degraded chlorophyll changes into many other colors
  • water supply to the leaves has been reduced
  • carotenoids and other pigments are still present in the leaves
  • sugars are sent to most of the cells of the leaves

Question 75

Question
What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?
Answer
  • An electron is excited.
  • ATP is synthesized from the energy absorbed.
  • A carboxylation reaction of the Calvin cycle occurs.
  • Electrons are stripped from NADPH.

Question 76

Question
As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?
Answer
  • It is lost as heat.
  • It excites electrons of the reaction center of photosystem I.
  • It is used to phosphorylate NAD+ to NADPH, the molecule that accepts electrons from photosystem I.
  • It is used to establish and maintain a proton gradient.

Question 77

Question
The final electron acceptor associated with photosystem I is _____.
Answer
  • water
  • NADPH
  • oxygen
  • NADP

Question 78

Question
The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?
Answer
  • oxygen
  • the electron carrier, plastocyanin
  • water
  • photosystem I

Question 79

Question
In the thylakoid membranes, the pigment molecules in a light-harvesting complex _____.
Answer
  • synthesize ATP from ADP and Pi
  • split water and release oxygen from the reaction-center chlorophyll
  • absorb and transfer light energy to the reaction-center chlorophyll
  • transfer electrons to ferredoxin and then NADPH

Question 80

Question
Which of the following are directly associated with photosystem I?
Answer
  • passing electrons to the cytochrome complex
  • extraction of hydrogen electrons from the splitting of water
  • generation of molecular oxygen
  • receiving electrons from the thylakoid membrane electron transport chain

Question 81

Question
Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be to _____.
Answer
  • test for CO2 fixation in the dark
  • test for liberation of O2 in the light
  • do experiments to generate an action spectrum
  • determine if they have thylakoids in the chloroplasts

Question 82

Question
What are the products of linear electron flow?
Answer
  • ADP and NADP+
  • ATP and NADPH
  • heat and fluorescence
  • ATP and P700

Question 83

Question
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will most directly affect the _____.
Answer
  • splitting of water
  • reduction of NADP+
  • synthesis of ATP
  • flow of electrons from photosystem II to photosystem I

Question 84

Question
In a plant cell, where are the ATP synthase complexes located?
Answer
  • inner mitochondrial membrane only
  • thylakoid membrane and plasma membrane
  • thylakoid membrane only
  • thylakoid membrane and inner mitochondrial membrane

Question 85

Question
In mitochondria, chemiosmosis moves protons from the intermembrane space into the matrix, whereas in chloroplasts, chemiosmosis moves protons from the _____.
Answer
  • thylakoid space to the stroma
  • matrix to the stroma
  • stroma to the thylakoid space
  • intermembrane space to the matrix

Question 86

Question
Which of the following statements best describes the relationship between photosynthesis and respiration?
Answer
  • Photosynthesis is catabolic; respiration is anabolic.
  • Photosynthesis occurs only in plants; respiration occurs only in animals.
  • Respiration runs the biochemical pathways of photosynthesis in reverse.
  • Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules

Question 87

Question
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during _____.
Answer
  • photosynthesis only
  • neither photosynthesis nor respiration
  • photosynthesis and respiration
  • respiration only

Question 88

Question
Carbon dioxide is split to form oxygen gas and carbon compounds _____.
Answer
  • during photosynthesis and respiration
  • in neither photosynthesis nor respiration
  • during photosynthesis
  • during respiration

Question 89

Question
What is the relationship between the wavelength of light and the quantity of energy per photon?
Answer
  • They are separate phenomena.
  • They are inversely related.
  • They are logarithmically related.
  • They have a direct, linear relationship.

Question 90

Question
P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?
Answer
  • It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.
  • It is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system.
  • It is the receptor for the most excited electron in either photosystem of photosynthesis.
  • It transfers its electrons to reduce NADP+ to NADPH.

Question 91

Question
Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?
Answer
  • They shield the sensitive chromosomes of the plant from harmful ultraviolet radiation.
  • They protect against oxidative damage from excessive light energy.
  • They serve as accessory pigments to increase light absorption.
  • They reflect orange light and enhance red light absorption by chlorophyll.

Question 92

Question
In a plant, the reactions that produce molecular oxygen (O2) take place in _____.
Answer
  • neither the light reactions nor the Calvin cycle
  • the Calvin cycle alone
  • the light reactions alone
  • the light reactions and the Calvin cycle

Question 93

Question
The accumulation of free oxygen in Earth's atmosphere began with the origin of _____.
Answer
  • land plants
  • chloroplasts in photosynthetic eukaryotic algae
  • life and respiratory metabolism
  • cyanobacteria using photosystem II

Question 94

Question
In its mechanism, photophosphorylation is most similar to _____.
Answer
  • reduction of NADP+
  • substrate-level phosphorylation in glycolysis
  • the Calvin cycle
  • oxidative phosphorylation in cellular respiration

Question 95

Question
Which process is most directly driven by light energy?
Answer
  • creation of a pH gradient by pumping protons across the thylakoid membrane
  • carbon fixation in the stroma
  • reduction
  • removal of electrons from chlorophyll molecules

Question 96

Question
Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
Answer
  • ATP and NADPH
  • H2O and O2
  • ADP, Pi, and NADP+
  • CO2 and glucose

Question 97

Question
Where does the Calvin cycle take place?
Answer
  • thylakoid membrane
  • interior of the thylakoid (thylakoid space)
  • outer membrane of the chloroplast
  • stroma of the chloroplast

Question 98

Question
What is the primary function of the Calvin cycle?
Answer
  • use NADPH to release carbon dioxide
  • synthesize simple sugars from carbon dioxide
  • split water and release oxygen
  • transport RuBP out of the chloroplast

Question 99

Question
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
Answer
  • NADPH → O2 → C O2
  • NADPH → electron transport chain → O2
  • H2O → NADPH → Calvin cycle
  • NADPH → chlorophyll → Calvin cycle

Question 100

Question
Which of the following does NOT occur during the Calvin cycle?
Answer
  • oxidation of NADPH
  • release of oxygen
  • consumption of ATP
  • regeneration of the CO2 acceptor
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