Question 1

Suppose atmospheric carbon dioxide levels rise dramatically in the future.How do you predict this will affect competition between C3 and C4 plants?

Accepted Answer

A)  C3 and C4 plants will compete equally, since both use the same stoichiometry of carbon dioxide to water in the overall photosynthetic reaction. 
B)  C3 plants will outcompete C4 plants, since C4 plants must use more energy in the carbon fixation phase of photosynthesis than C3 plants. 
C)  C3 plants will outcompete C4 plants, since there are many more species of C3 plants than C4 species. 
D)  C4 plants will outcompete C3 plants, since C3 plants are not hampered by photorespiration and C4 plants are hampered by this rubisco activity. 
E)  C3 plants will outcompete C4 plants, since C3 plants can store fixed carbon in four-carbon organic molecules in mesophyll cells until needed for Calvin cycle reactions. 
A)  C3 and C4 plants will compete equally, since both use the same stoichiometry of carbon dioxide to water in the overall photosynthetic reaction. 
B)  C3 plants will outcompete C4 plants, since C4 plants must use more energy in the carbon fixation phase of photosynthesis than C3 plants. 
C)  C3 plants will outcompete C4 plants, since there are many more species of C3 plants than C4 species. 
D)  C4 plants will outcompete C3 plants, since C3 plants are not hampered by photorespiration and C4 plants are hampered by this rubisco activity. 
E)  C3 plants will outcompete C4 plants, since C3 plants can store fixed carbon in four-carbon organic molecules in mesophyll cells until needed for Calvin cycle reactions.

Question 2

Refer to the table below.   The table contains data collected by Melvin Calvin and his colleagues during experiments designed to trace the pathway of carbon in photosynthesis.Carbon dioxide labeled with carbon-14 was incubated with algal cells under different conditions outlined in the table before the cells were harvested and their contents analyzed for the amount of carbon-14 label in various compounds.Quantities of radioactivity in three compounds are listed in the table.Which statement correctly explains why the amount of carbon-14 present in 3PG increased after 30 seconds of dark?

Accepted Answer

A)  Enough ATP and NADPH were synthesized during the period of light to allow synthesis of 3PG. 
B)  The enzyme rubisco is able to function for a short period in the dark following exposure to light. 
C)  The Calvin cycle can continue to run indefinitely in the dark after a period of illumination. 
D)  The Calvin cycle enzymes function better in the dark than in the light, which explains why the reactions they catalyze are called light-independent reactions. 
E)  The increase reflects a lag time that occurs once Calvin cycle enzymes are activated by light. 
A)  Enough ATP and NADPH were synthesized during the period of light to allow synthesis of 3PG. 
B)  The enzyme rubisco is able to function for a short period in the dark following exposure to light. 
C)  The Calvin cycle can continue to run indefinitely in the dark after a period of illumination. 
D)  The Calvin cycle enzymes function better in the dark than in the light, which explains why the reactions they catalyze are called light-independent reactions. 
E)  The increase reflects a lag time that occurs once Calvin cycle enzymes are activated by light.

Question 3

The carbon from CO2 is

Accepted Answer

A)  oxidized during the Calvin cycle. 
B)  reduced during the Calvin cycle. 
C)  lost during NADP+ reduction. 
D)  integrated into ATP. 
E)  added to 3PG. 
A)  oxidized during the Calvin cycle. 
B)  reduced during the Calvin cycle. 
C)  lost during NADP+ reduction. 
D)  integrated into ATP. 
E)  added to 3PG.

Question 4

In C4 plants, starch grains are found in the chloroplasts of

Accepted Answer

A)  the stems. 
B)  mesophyll cells. 
C)  the intercellular region. 
D)  the epidermis. 
E)  bundle sheath cells. 
A)  the stems. 
B)  mesophyll cells. 
C)  the intercellular region. 
D)  the epidermis. 
E)  bundle sheath cells.

Question 5

When a photon meets a molecule, which of the following cannot happen?

Accepted Answer

A)  The photon may be scattered or reflected. 
B)  The photon may excite an electron in the molecule to a shell farther from the nucleus. 
C)  The photon may be transmitted. 
D)  The photon may be absorbed. 
E)  The photon may lower the ground state of the absorbing molecule. 
A)  The photon may be scattered or reflected. 
B)  The photon may excite an electron in the molecule to a shell farther from the nucleus. 
C)  The photon may be transmitted. 
D)  The photon may be absorbed. 
E)  The photon may lower the ground state of the absorbing molecule.

Question 6

What determines whether rubisco acts as an oxygenase or a carboxylase?

Accepted Answer

A)  Rubisco has ten times more affinity for O2 than for CO2; therefore, it favors O2 fixation. 
B)  If O2 is relatively abundant, rubisco acts as a carboxylase. 
C)  If O2 predominates, rubisco fixes it, and the Calvin cycle occurs. 
D)  Oxygenase activity is more likely at low temperatures. 
E)  As the ratio of CO2 to O2 falls in the leaf, the reaction of rubisco with O2 is favored. 
A)  Rubisco has ten times more affinity for O2 than for CO2; therefore, it favors O2 fixation. 
B)  If O2 is relatively abundant, rubisco acts as a carboxylase. 
C)  If O2 predominates, rubisco fixes it, and the Calvin cycle occurs. 
D)  Oxygenase activity is more likely at low temperatures. 
E)  As the ratio of CO2 to O2 falls in the leaf, the reaction of rubisco with O2 is favored.

Question 7

A new plant is discovered in the desert and determined to be either a C4 or CAM plant.Which measurement will best help you to determine whether it is a C4 or CAM plant?

Accepted Answer

A)  The rate of photorespiration 
B)  The number of stomata 
C)  The activity of PEP carboxylase in the day and at night 
D)  The amount of oxaloacetate produced in a 24-hour period 
E)  The amount of soil moisture 
A)  The rate of photorespiration 
B)  The number of stomata 
C)  The activity of PEP carboxylase in the day and at night 
D)  The amount of oxaloacetate produced in a 24-hour period 
E)  The amount of soil moisture

Question 8

Photosynthesis

Accepted Answer

A)  uses 100 percent of the sunlight that reaches Earth. 
B)  is a very efficient biochemical pathway. 
C)  utilizes all wavelengths of light. 
D)  converts 90 percent of light energy to chemical energy. 
E)  utilizes only a small portion of the energy of sunlight. 
A)  uses 100 percent of the sunlight that reaches Earth. 
B)  is a very efficient biochemical pathway. 
C)  utilizes all wavelengths of light. 
D)  converts 90 percent of light energy to chemical energy. 
E)  utilizes only a small portion of the energy of sunlight.

Question 9

During photorespiration, rubisco uses _______ as a substrate.

Accepted Answer

A)  CO2 
B)  O2 
C)  glyceraldehyde 3-phosphate 
D)  3-phosphoglycerate 
E)  NADPH 
A)  CO2 
B)  O2 
C)  glyceraldehyde 3-phosphate 
D)  3-phosphoglycerate 
E)  NADPH

Question 10

Which graph illustrates the expected changes in a chloroplast's stroma pH in response to a cycle of light and dark?

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 11

Refer to the table below.   Data in the table summarize a set of experiments in which a plant species was treated with plain water or with additions of compound X or compound Y to its daily waterings.After 7 days of treatment, chloroplasts from the plants were isolated, and their abilities to carry out water oxidation, ATP production, and NADP+ reduction were measured.The number of "+" symbols is proportional to the level of biological activity observed.Both cyclic and noncyclic photophosphorylation processes are active in this plant species.Which hypothesis concerning the mode of action of compounds X and Y is consistent with the data?

Accepted Answer

A)  Compound X and compound Y are both inhibitors of ATP synthase. 
B)  Compound X and compound Y are both inhibitors of NADP+ reductase. 
C)  Compound X is an NADP+ reductase inhibitor, and compound Y causes protons to leak through the thylakoid membrane. 
D)  Compound X causes protons to leak through the thylakoid membrane, and compound Y is an ATP synthase inhibitor. 
E)  Compound X is an ATP synthase inhibitor, and compound Y causes protons to leak through the thylakoid membrane. 
A)  Compound X and compound Y are both inhibitors of ATP synthase. 
B)  Compound X and compound Y are both inhibitors of NADP+ reductase. 
C)  Compound X is an NADP+ reductase inhibitor, and compound Y causes protons to leak through the thylakoid membrane. 
D)  Compound X causes protons to leak through the thylakoid membrane, and compound Y is an ATP synthase inhibitor. 
E)  Compound X is an ATP synthase inhibitor, and compound Y causes protons to leak through the thylakoid membrane.

Question 12

Which of the following occurs during the light-independent reactions of photosynthesis?

Accepted Answer

A)  Water is converted into hydrogen and oxygen. 
B)  CO2 is converted into sugars. 
C)  Chlorophyll acts as an enzyme. 
D)  Nothing occurs; the plant rests in the dark. 
E)  CO2 is split into carbon and oxygen. 
A)  Water is converted into hydrogen and oxygen. 
B)  CO2 is converted into sugars. 
C)  Chlorophyll acts as an enzyme. 
D)  Nothing occurs; the plant rests in the dark. 
E)  CO2 is split into carbon and oxygen.

Question 13

Which statement can be used to describe PEP carboxylase but cannot be used to describe rubisco?

Accepted Answer

A)  Carbon dioxide is a substrate. 
B)  Enzymatic activity is found in the cytosol. 
C)  Enzymatic activity is independent of oxygen concentration. 
D)  A four-carbon molecule is the product. 
E)  It is found in CAM plants. 
A)  Carbon dioxide is a substrate. 
B)  Enzymatic activity is found in the cytosol. 
C)  Enzymatic activity is independent of oxygen concentration. 
D)  A four-carbon molecule is the product. 
E)  It is found in CAM plants.

Question 14

As global atmospheric CO2 levels continue to rise,

Accepted Answer

A)  C4 plants will have an advantage over C3 plants. 
B)  C3 plants will have an advantage over C4 plants. 
C)  the growth rates of rice and wheat will decrease. 
D)  photorespiration will increase. 
E)  CAM plants will have an advantage over C3 plants. 
A)  C4 plants will have an advantage over C3 plants. 
B)  C3 plants will have an advantage over C4 plants. 
C)  the growth rates of rice and wheat will decrease. 
D)  photorespiration will increase. 
E)  CAM plants will have an advantage over C3 plants.

Question 15

Refer to the flowchart below.   Note that there is an empty box in this flowchart.Adding _______ to this box will complete the flowchart.

Accepted Answer

The answer of Refer to the flowchart below.  ...

Question 16

Metabolic pathways are somewhat like roadways: A metabolic path may be one-way or two-way.It may contain intersections that connect many different pathways, or it may be isolated, with a dead end, and only connect to one other pathway.What roadway analogy could be used to describe the location of glyceraldehyde 3-phosphate (product of the Calvin cycle) in plant cell metabolism?

Accepted Answer

A)  At the end of a dead-end street 
B)  At the intersection of two rarely traveled one-way streets 
C)  At the intersection of several busy superhighways 
D)  In the middle of a long heavily traveled road with no intersections 
E)  In the middle of a bridge that spans a very wide river 
A)  At the end of a dead-end street 
B)  At the intersection of two rarely traveled one-way streets 
C)  At the intersection of several busy superhighways 
D)  In the middle of a long heavily traveled road with no intersections 
E)  In the middle of a bridge that spans a very wide river

Question 17

Refer to the table below showing observations from experiments conducted on three types of pea plants.One type of pea plant contained a mutation in the gene encoding thioredoxin that resulted in zero production of the protein thioredoxin.Another type contained two mutations: the same thioredoxin mutation as in the previous type and a mutation in the gene encoding the Calvin cycle enzyme phosphoribulokinase (PRK) that did not affect its expression.The third type contained no mutations in either gene and was designated as "wild type." Before the experiments, all plants were kept on a 14-hour light/10-hour dark cycle for several weeks.   In conducting the experiments, researchers excised leaves either toward the end of a light cycle or toward the end of a dark cycle.Chloroplasts were then isolated and lysed to release the contents of the stroma, and PRK was assayed to determine its catalytic activity.Which statement about thioredoxin is consistent with these data?

Accepted Answer

A)  Thioredoxin is an electron carrier protein that participates in the electron transport chain during photophosphorylation. 
B)  Thioredoxin is a regulatory molecule, becoming activated via light-induced changes and then activating PRK by shifting it from an inactive to an active conformation. 
C)  Thioredoxin is a regulatory molecule, shutting down Calvin cycle reactions by acting as an alternative to NADP+ as the final electron acceptor during the light reactions. 
D)  Thioredoxin is an enzyme that functions in carbon fixation as an alternative to the Calvin cycle enzyme rubisco. 
E)  Thioredoxin is an integral protein component of the thylakoid membrane that ensures that the membrane remains impermeable to protons. 
A)  Thioredoxin is an electron carrier protein that participates in the electron transport chain during photophosphorylation. 
B)  Thioredoxin is a regulatory molecule, becoming activated via light-induced changes and then activating PRK by shifting it from an inactive to an active conformation. 
C)  Thioredoxin is a regulatory molecule, shutting down Calvin cycle reactions by acting as an alternative to NADP+ as the final electron acceptor during the light reactions. 
D)  Thioredoxin is an enzyme that functions in carbon fixation as an alternative to the Calvin cycle enzyme rubisco. 
E)  Thioredoxin is an integral protein component of the thylakoid membrane that ensures that the membrane remains impermeable to protons.

Question 18

Refer to the figure below.   The figure compares the inputs and outputs of the carboxylase and oxygenase reactions catalyzed by rubisco.Which compound fits in the box containing a question mark?

Accepted Answer

A)  CO2 
B)  H2O 
C)  O2 
D)  ATP 
E)  NADPH 
A)  CO2 
B)  H2O 
C)  O2 
D)  ATP 
E)  NADPH

Question 19

Refer to the graph below summarizing results from experiments on lysed chloroplasts.These are chloroplasts that have been isolated from green plant cells and then broken open to release all of the chloroplast contents into a mixture in a test tube.The mixture contained rubisco enzymes that were tested for their level of catalytic activity under the four conditions shown in the graph.DCMU is an organic molecule that inhibits the photosystem II electron transport chain.   Which statement about photosynthesis is supported by the data presented in the graph?

Accepted Answer

A)  Rubisco undergoes activation in response to light and involves a mechanism mediated by electron transport. 
B)  The Calvin cycle reactions require energy input in the form of NADPH and ATP, which are generated using energy from light. 
C)  Carbohydrates produced in photosynthesis are used to make other molecules, including amino acids, lipids, and the building blocks of nucleic acids. 
D)  The initial reaction in the Calvin cycle adds the carbon in CO2 to ribulose 1,5-bisphosphate (RuBP). 
E)  ATP synthase couples the formation of ATP to the movement of protons from a position of high concentration to a position of low concentration. 
A)  Rubisco undergoes activation in response to light and involves a mechanism mediated by electron transport. 
B)  The Calvin cycle reactions require energy input in the form of NADPH and ATP, which are generated using energy from light. 
C)  Carbohydrates produced in photosynthesis are used to make other molecules, including amino acids, lipids, and the building blocks of nucleic acids. 
D)  The initial reaction in the Calvin cycle adds the carbon in CO2 to ribulose 1,5-bisphosphate (RuBP). 
E)  ATP synthase couples the formation of ATP to the movement of protons from a position of high concentration to a position of low concentration.

Question 20

Refer to the table below, which contains data collected using the same techniques that Calvin and his colleagues used to determine the pathway of carbon atoms during photosynthesis.In this experiment, the starting material was a synthesized compound that contained carbon-14.This 14C-labeled compound was supplied to a living culture of algae at time zero.Then, at 5-second intervals, samples of the culture were harvested and extracted.The extracts were subjected to two-dimensional chromatography, and the resulting spots were numbered and measured for radioactivity.A "0" indicates negligible radioactivity, while a "+" indicates measurable radioactivity; the greater the number of "+" symbols, the greater the radioactivity detected.   Based on these results, what is the sequence of compounds in the metabolic pathway?

Accepted Answer

A)  3 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 2 F1F1F1S1F1F1F10 4 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 6 
B)  4 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 3 F1F1F1S1F1F1F10 2 
C)  1 F1F1F1S1F1F1F10 4 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 3 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 2 
D)  2 F1F1F1S1F1F1F10 3 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 4 
E)  4 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 2 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 3 
A)  3 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 2 F1F1F1S1F1F1F10 4 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 6 
B)  4 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 3 F1F1F1S1F1F1F10 2 
C)  1 F1F1F1S1F1F1F10 4 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 3 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 2 
D)  2 F1F1F1S1F1F1F10 3 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 4 
E)  4 F1F1F1S1F1F1F10 1 F1F1F1S1F1F1F10 5 F1F1F1S1F1F1F10 2 F1F1F1S1F1F1F10 6 F1F1F1S1F1F1F10 3

Exam 10: Photosynthesis: Energy From Sunlight

Suppose atmospheric carbon dioxide levels rise dramatically in the future.How do you predict this will affect competition between C3 and C4 plants?

The carbon from CO2 is

In C4 plants, starch grains are found in the chloroplasts of

When a photon meets a molecule, which of the following cannot happen?

What determines whether rubisco acts as an oxygenase or a carboxylase?

A new plant is discovered in the desert and determined to be either a C4 or CAM plant.Which measurement will best help you to determine whether it is a C4 or CAM plant?

Photosynthesis

During photorespiration, rubisco uses _______ as a substrate.

Which graph illustrates the expected changes in a chloroplast's stroma pH in response to a cycle of light and dark?

Which of the following occurs during the light-independent reactions of photosynthesis?

Which statement can be used to describe PEP carboxylase but cannot be used to describe rubisco?

As global atmospheric CO2 levels continue to rise,

Refer to the flowchart below. Note that there is an empty box in this flowchart.Adding _______ to this box will complete the flowchart.

Refer to the figure below. The figure compares the inputs and outputs of the carboxylase and oxygenase reactions catalyzed by rubisco.Which compound fits in the box containing a question mark?

Studying Life

Small Molecules and the Chemistry of Life

Proteins, Carbohydrates, and Lipids

Nucleic Acids and the Origin of Life

Cells: the Working Units of Life

Cell Membranes

Cell Communication and Multicellularity

Energy, Enzymes, and Metabolism

Pathways That Harvest Chemical Energy

The Cell Cycle and Cell Division

Inheritance, Genes, and Chromosomes

Dna and Its Role in Heredity

From Dna to Protein: Gene Expression

Gene Mutation and Molecular Medicine

Regulation of Gene Expression

Genomes

Recombinant Dna and Biotechnology

Mechanisms of Evolution

Reconstructing and Using Phylogenies

Speciation

Evolution of Genes and Genomes

The History of Life on Earth

Bacteria, Archaea, and Viruses

The Origin and Diversification of Eukaryotes

Plants Without Seeds: From Water to Land

The Evolution of Seed Plants

The Evolution and Diversity of Fungi

Animal Origins and the Evolution of Body Plans

Protostome Animals

Deuterostome Animals

The Plant Body

Transport in Plants

Plant Nutrition

Regulation of Plant Growth

Reproduction in Flowering Plants

Plant Responses to Environmental Challenges

Physiology, Homeostasis, and Temperature Regulation

Animal Hormones

Immunology: Animal Defense Systems

Animal Reproduction

Animal Development

Neurons, Glia, and Nervous Systems

Sensory Systems

The Mammalian Nervous System: Structure and Higher Functions

Musculoskeletal Systems

Gas Exchange

Circulatory Systems

Nutrition, Digestion, and Absorption

Salt and Water Balance and Nitrogen Excretion

Animal Behavior

The Physical Environment and Biogeography of Life

Populations

Species Interactions

Communities

Ecosystems

A Changing Biosphere

Filters

Suppose atmospheric carbon dioxide levels rise dramatically in the future.How do you predict this will affect competition between C₃ and C₄ plants?

The carbon from CO₂ is

In C₄ plants, starch grains are found in the chloroplasts of

A new plant is discovered in the desert and determined to be either a C₄ or CAM plant.Which measurement will best help you to determine whether it is a C₄ or CAM plant?

As global atmospheric CO₂ levels continue to rise,