Chapter 10. Photosynthesis: Energy from Sunlight (HOMEWORK & QUIZ)

What percentage of sunlight is used as chemical energy for carbon fixation?

5

Match the structure/location in the chloroplast with its name and the chemical reaction that takes place there.

A = thylakoids, equation 2. B= Stroma, equation 1

How many six-carbon sugar molecules are produced by the Calvin cycle when 18 CO2 are fixed? A) 3 B) 9 C) 18 D) 36 E) 44

A) 3

Conversion of carbon dioxide into carbohydrates relies on energy from A) ATP B) NAD+ C) NAPD+ D) ADP E) NADH

A) ATP

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 (G3P, product of the Calvin cycle) in plant cell metabolism? A) At the intersection of several busy superhighways B) In the middle of a long heavily traveled road with no intersections C) At the intersection of two rarely traveled one-way streets D)At the end of a dead-end street In the middle of a bridge that spans a very wide river

A) At the intersection of several busy superhighways

Corn, Bermuda grass, and sugarcane are examples of A) C4 plants. B) succulents. C) CAM plants. D) C3 plants. E) desert plants.

A) C4 plants.

The most important wavelengths of light for photosynthesis are

the visible wavelengths between 400 and 525 nm and between 600 and 700 nm.

12 H2S + 6 CO2 + light → C6H12O6 + 12 S + 6 H2O

uses H2S as an electron donor.

12 H2O → 24 H+ + 24 e- + 6 O2

water is oxidized.

Which enzyme catalyzes the first step in the Calvin cycle? A) 3PG B) Glyceraldehyde-3-phosphate C) RuBP D) PEP E) Rubisco

E) Rubisco

A(n) _______ moves from a low energy level to a higher energy level to produce this excited-state chlorophyll molecule. A) electron B) water molecule C) photon D) proton E) ATP molecule

A) electron

C4 plants differ from C3 plants because C3 plants _________, while C4 plants __________. A) have mesophyll cells that fix CO2 and contain the Calvin cycle; have mesophyll cells that fix CO2 and bundle sheath cells that contain the Calvin cycle B) produce a four-carbon intermediate after CO2 fixation; produce a three-carbon intermediate after CO2 fixation C) gain CO2 via photorespiration; lose CO2 via photorespiration D) can concentrate the CO2 by regulating the stomata closure; can concentrate CO2 at night E) concentrate CO2 near rubisco; cannot concentrate CO2 near rubisco

A) have mesophyll cells that fix CO2 and contain the Calvin cycle; have mesophyll cells that fix CO2 and bundle sheath cells that contain the Calvin cycle

The chemical energy stored from photosynthesis represents ________ percent of the total energy of the sunlight hitting a green leaf. A)5 B) 10 C) 30 D) 50 E) 100

A)5

It has been estimated that only about 5 percent of the sun's energy that reaches Earth is captured as chemical energy in the form of carbohydrates via photosynthesis. How much of the sun's energy reaching Earth do you estimate is stored in the cells of nonphotosynthetic organisms?

Above 0 but well below 5 percent

Plant cellular respiration occurs

All the time

What percentage of sunlight is used as chemical energy for carbon fixation? A) 0 B) 5 C) 10 D) 30 E) 100

B) 5

Which reaction taking place in a chloroplast directly depends on light? A) A reaction producing carbohydrate B) A reaction action producing oxygen C) A reaction using carbon dioxide D) A reaction using NADPH E) A reaction using ATP

B) A reaction action producing oxygen

Photophosphorylation requires A) darkness. B) ATP synthase. C) a flow of electrons from photosystem I to photosystem II. D) a low concentration of protons in the thylakoid lumen. E) the production of NADP+.

B) ATP synthase.

What are stomata? A) Adjustable pores on a leaf that allow CO2 to enter and only O2 to exit B) Adjustable pores on a leaf that allow CO2 to enter and O2 and water to exit C) Parts of the chloroplast where carbon-fixation reactions occur D) Types of organisms that use sulfide ions as electron donors E) Photosynthetic structures in prokaryotes

B) Adjustable pores on a leaf that allow CO2 to enter and O2 and water to exit

Photosystem I (PSI) and photosystem II (PSII) have similarities and differences. Which statement comparing these two systems is true? A) The energy trapped in the excited states of both PSI and PSII is used to reduce NADP+. B) Both PSI and PSII reaction centers draw electrons from electron donors after they are excited by photons and oxidized. C) PSII and PSI are both located in the stroma of the chloroplast along with the electron transport chain. D) PSI and PSII have reaction center chlorophylls that absorb light at the same wavelengths. E) The excited chlorophyll (Chl*) of a PSI reaction center loses an electron and is re-reduced by water, while the Chl* of a PSII reaction center passes its electrons via intermediates to NADP+.

B) Both PSI and PSII reaction centers draw electrons from electron donors after they are excited by photons and oxidized.

A species of plant is found to use both cyclic and noncyclic photophosphorylation. Which outcome is most likely for this plant if cyclic photophosphorylation is completely inhibited? A) It will produce leaves with much greater surface area. B) It will experience impaired growth and development. C) It will grow taller and heavier than normal. D) It will not experience any change that can be observed in its outward appearance. E) It will produce more branches with greater numbers of leaves per plant.

B) It will experience impaired growth and development.

Water molecules labeled with 18O were added to the water given to a plant and subsequently taken up by the plant's roots. If molecule(s) associated with the plant were analyzed at a later time, which would you expect to contain 18O? A) Water B) Oxygen C) Carbon dioxide D) Carbohydrate E) Lipid

B) Oxygen

Some plants have the capacity to carry out both cyclic and noncyclic photophosphorylation at the same time. They also have the ability to regulate the rates of these two processes. Which is a correct statement that explains an advantage of this type of regulation? A) The plant can take advantage of a broader range of visible light wavelengths by shifting back and forth between the two processes. B) The plant can shift flow of electrons through the two processes to shift the ratio of ATP to NADPH being produced to best meet metabolic demands. C) The plant can generate heat in place of ATP synthesis as needed, by shifting the flow of electrons between the two processes. D) The plant can conserve space in the chloroplast membrane by shifting gene expression to the process with fewer components. E) The plant can avoid the effects of chemical inhibitors of ATP synthase used as herbicides, by shifting between the two processes.

B) The plant can shift flow of electrons through the two processes to shift the ratio of ATP to NADPH being produced to best meet metabolic demands.

When the ratio of O2 to CO2 within their leaves _________, C3 plants undergo a shift toward more _______ and less _________. A) Increases; growth; carbon fixation B) increases; photorespiration; carbon fixation C) decreases; photorespiration; growth D) increases; carbon fixation; photorespiration E) decreases; photorespiration; carbon fixation

B) increases; photorespiration; carbon fixation

A photosynthetic action spectrum plots measurements of A) the relative rate of photosynthesis as a function of time. B) the relative rate of photosynthesis as a function of wavelength. C) the relative absorption of light as a function of wavelength. D) the relative absorption of light as a function of time. E) the relative absorption of light of a chlorophyll molecule as a function of wavelength.

B) the relative rate of photosynthesis as a function of wavelength.

What part of the electromagnetic spectrum has more energy than yellow light?

Blue light

Which type of plant increases the concentration of CO2 around the rubisco enzyme prior to carbon fixation by rubisco? A) Plants that undergo cellular respiration B) C3 C) C4 D) CAM E) Plants that undergo photorespiration

C) C4

Photosynthesis and cellular respiration are connected through which pathways? A) Fatty acid synthesis and Calvin cycle B) Gluconeogenesis and glycolysis C) Calvin cycle and glycolysis D) Glycolysis and citric acid cycle E) Citric acid cycle and Calvin cycle

C) Calvin cycle and glycolysis

In the overall reaction describing photosynthesis, which class of compounds is represented in one of the products? A) Lipids B) Sterols C) Carbohydrates D) Fatty acids E) Proteins

C) Carbohydrates

If four molecules of ribulose bisphosphate (RuBP) were added to a solution containing rubisco and CO2, what would be the products of the reaction? A) Four molecules of glycolate and four molecules of 3PG B) Eight molecules of G3P C) Eight molecules of 3PG D) Six molecules of 3PG E) Four molecules of 3PG

C) Eight molecules of 3PG

The Calvin cycle is linked to glycolysis by which intermediate? A) Glycerol B) Pyruvate C) Glyceraldehyde 3-phosphate (G3P) D) Acetyl CoA E) Sucrose

C) Glyceraldehyde 3-phosphate (G3P)

The immediate source of energy for ATP synthesis in chloroplasts is __________, while the ultimate source of energy for ATP synthesis in chloroplasts is __________. A) NADPH; energized chlorophylls B) NADPH; electron transport C) a proton gradient; light D) electron transport; a proton gradient E) light; electron transport

C) a proton gradient; light

Light is a form of A) chemical energy. B) chlorophyll. C) electromagnetic radiation. D) magnetic radiation. E) an absorption spectrum.

C) electromagnetic radiation

Careful measurements of pH on each side of the thylakoid membrane have shown that the interior lumen is lower in pH than the exterior. This observation provides one piece of evidence that supports the mechanism for the _______ in photosynthesis. A) transfer of light energy to the reaction center of photosystem I B) transfer of light energy to the reaction center of photosystem II C) production of ATP by chemiosmosis D) entrance of CO2 into the Calvin cycle E) reduction of NADP+ to NADPH

C) production of ATP by chemiosmosis

Plants that carry out crassulacean acid metabolism (CAM) differ from C4 plants in that A) they do not contain PEP carboxylase. B) they do not contain rubisco. C) their stomata are open at night. D) they do not carry out the Calvin cycle. E) they do not need ATP for photosynthesis.

C) their stomata are open at night.

Wheat, roses, and rice are examples of

C3 plants

Which substance has not been identified as an electron donor in various organisms that carry out either oxygenic or anoxygenic photosynthesis? a) Water b) Ferrous iron c) Sulfide ions d) Hydrogen e) Carbon dioxide

Carbon dioxide

How many micromoles of 3-phosphoglycerate would be formed by rubisco if 4 μM of RuBP were added to the solution in the presence of CO2 and the absence of O2? A) 1 B) 2 C) 4 D) 8 E) 16

D) 8

Which is a metabolic pathway that links the Calvin cycle to lipid biosynthesis? A) RuMP → RuBP → nucleic acids → fatty acids → glycolysis → glycerol → lipids B) G3P → glycolysis → acetyl CoA → citric acid cycle → α-ketoglutarate → lipids C) 3PG → sucrose → hexose P → pyruvate → acetyl CoA → glycolysis → fatty acids → lipids D) G3P → glycolysis → pyruvate → acetyl CoA → fatty acids → lipids E) 3PG → glycolysis → glycerol → RuMP → nucleotides → acetyl CoA → lipids

D) G3P → glycolysis → pyruvate → acetyl CoA → fatty acids → lipids

Glyceraldehyde 3-phosphate (G3P) A) Is a four-carbon molecule. B) Is insoluble in water. C) contains carbon and phosphate but no oxygen atoms. D) Is converted to glucose in the chloroplast and cytoplasm. E) Is exported from the cytoplasm to the chloroplast.

D) Is converted to glucose in the chloroplast and cytoplasm.

What role does water play in photosynthesis? A) Its atoms end up in sugar. B) It is only a reactant in the photosynthetic process. C) It acts as an electron acceptor. D) It undergoes no net chemical change. E) It is the source of oxygen atoms in the product O2.

D) It is the source of oxygen atoms in the product O2.

In the 1930s, researchers worked with green algae to experimentally determine the minimum light exposure in a single flash that produced the maximal oxygen output. When the researchers calculated the amount of chlorophyll present, they found that there were 300 times more chlorophyll molecules present than would be needed to produce this amount of oxygen with a single light flash. How are these observations consistent with the way that scientists today describe the light-harvesting complex in chloroplasts? A) The observations explain how energy is transferred from the light-harvesting complex to the Calvin cycle. B) The observations explain why water is the source of oxygen that is produced during the reaction taking place inside one light-harvesting complex. C) The observations explain how light energy is ultimately converted to chemical energy within the light-harvesting complex. D) The observations explain how most chlorophyll molecules act as antennae to absorb photons and then redirect this energy to a single chlorophyll molecule at the center of the complex. E) The observations explain why most chlorophyll molecules are static and not reactive inside the light-harvesting complex.

D) The observations explain how most chlorophyll molecules act as antennae to absorb photons and then redirect this energy to a single chlorophyll molecule at the center of the complex.

Which statement about the light-independent reactions (carbon-fixation reactions) of photosynthesis is true? A) ATP is not needed in light-independent reactions. B) Light-independent reactions take place in the chloroplast thylakoids. C) NADPH is created by light-independent reactions. D) The term "light-independent reactions" refers to the pathways by which CO2 is reduced to carbohydrates. E) Light-independent reactions operate in the dark.

D) The term "light-independent reactions" refers to the pathways by which CO2 is reduced to carbohydrates.

The first product of CO2 fixation in C4 plants is A) rubisco. B) 3-phosphoglycerate (3PG). C) RuBP. D) oxaloacetate. E) PEP.

D) oxaloacetate.

Light-harvesting complexes were isolated and analyzed from a red alga. It is likely that the alga got its color from A) chlorophyll a because it reflects green light. B) beta-carotene because it absorbs red light. C) chlorophyll b because it absorbs blue and red light. D) phycobilins because they absorb yellow-green, yellow, and orange light. E) chlorophyll a because it absorbs red light.

D) phycobilins because they absorb yellow-green, yellow, and orange light

The first step in noncyclic electron transport includes A) NADPH being produced. B) water being oxidized by oxygen. C) electrons flowing through plastoquinone (PQ). D) the P680 reaction center being excited by a photon. E) protons being actively transported into the thylakoid lumen.

D) the P680 reaction center being excited by a photon.

In the equation, 12 H2O → 24 H+ + 24 e- + 6 O2, A) water is reduced. B) oxygen ions are produced. C) electrons are gained by water. D) water is oxidized. E) oxygen atoms are oxidized.

D) water is oxidized.

In photosynthesis, ATP is generated in the light reactions and used in the light-independent reactions as a reducing agent to reduce carbon dioxide to form carbohydrates, which the plant can use for structure and energy. Which word or phrase could be changed or deleted to eliminate the error? A) "carbon dioxide" changed to "sugars" B) "ATP" changed to "NADP+" C) "reducing agent" changed to "oxidizing agent" D) "and energy" deleted E) "ATP" changed to "NADPH"

E) "ATP" changed to "NADPH"

While reading a biology resource text, a student noticed two terms used erroneously in the statement: Light energy is converted to chemical energy with the production of carrier molecules ATP and NADPH during the endergonic light-dependent reactions of photosynthesis. These carrier molecules provide the energy and reducing power for the synthesis of carbon-carbon bonds during the exergonic carbon-fixation reactions of photosynthesis. Which terms are used erroneously in the text? A) Light-dependent and light-independent B) Chemical energy and reducing power C) ATP and NADPH D) Carrier molecules and carbon-carbon bonds E) Endergonic and exergonic

E) Endergonic and exergonic

Which statement about chlorophyll is true? A) Chlorophyll is absent from light-harvesting complexes, also known as antenna systems. B) Most of the chlorophyll in a plant participates in an oxidation-reduction reaction. C) Chlorophyll contains Fe2+. D) Chlorophyll appears green because it absorbs green light. E) Most of the chlorophyll in a plant functions to gather light.

E) Most of the chlorophyll in a plant functions to gather light.

Which statement concerning PEP carboxylase and rubisco is true ? A) PEP carboxylase catalyzes a carboxylase reaction, but rubisco does not. B) PEP carboxylase is found in C4 plants, but rubisco is not. C) PEP carboxylase is an enzyme, but rubisco is not. D) PEP carboxylase and rubisco both use oxygen as a substrate. E) PEP carboxylase requires a three-carbon reactant, while rubisco requires a five-carbon reactant.

E) PEP carboxylase requires a three-carbon reactant, while rubisco requires a five-carbon reactant.

Which statement is false regarding the Calvin cycle? A) ATP is required during carbon fixation, reduction, sugar production, and regeneration of RuBP. B) NADPH is required for oxidation and sugar production. C) Light does not have an effect on the Calvin cycle. D) Twelve ATP molecules are required for every 6 CO2 fixed. E) Twelve NADPH are required for every 6 CO2 fixed.

E) Twelve NADPH are required for every 6 CO2 fixed.

In addition to driving the synthesis of ATP and the reduction of NADP+ to NADPH, light stimulates the Calvin cycle by __________ and __________. A) increasing the pH of the stroma; oxidation of some Calvin cycle enzymes B) decreasing the pH of the stroma; oxidation of some Calvin cycle enzymes C) increasing the pH of the thylakoid lumen; reduction of some Calvin cycle enzymes D) decreasing the pH of the stroma; reduction of some Calvin cycle enzymes E) increasing the pH of the stroma; reduction of some Calvin cycle enzymes

E) increasing the pH of the stroma; reduction of some Calvin cycle enzymes

In oxygenic photosynthesis, water is A) reduced to hydrogen gas (H2) in the light. B) reduced to oxygen gas (O2) in the light. C) oxidized to oxygen gas (O2) in the dark. D) reduced to hydrogen gas (H2) in the dark. E) oxidized to oxygen gas (O2) in the light.

E) oxidized to oxygen gas (O2) in the light.

Melvin Calvin and colleagues determined the steps of the Calvin cycle through A) characterization of mutant organisms using genetic engineering techniques. B) analysis of molecules using mass spectroscopy. C) identification of enzymes using modern genetics methods. D) observations of cells using microscopy. E) separation of molecules using paper chromatography.

E) separation of molecules using paper chromatography.

Which statement about rubisco is true?

It generates a six-carbon molecule that splits into two molecules of 3PG.

Which statement about the light-independent reactions of photosynthesis is false?

Light independent reactions operate in the dark

In noncyclic photophosphorylation, electrons flow in a one-way path from water to

NADP+.

In oxygenic photosynthesis, water is

Oxidized to oxygen gas in the light

To study the mechanism of excitation in the reaction center of a photosystem, on what timescale would you need to capture data?

Picoseconds (10-12 sec)

The immediate source of energy for ATP synthesis in chloroplasts is _______, while the ultimate source of energy for ATP synthesis in chloroplasts is _______.

a proton gradient; light

If stomata on a plant leaf close, then a) tarch production increases. b) sugar production increases. c) oxygen production increases. d) photosynthesis rates decrease. e) photosynthesis rates increase.

d) photosynthesis rates decrease.

Photosynthetic efficiency is affected by the

orientation of a plant's leaves to the sun.

The first enzyme in C4 carbon fixation is

phosphoenolpyruvate (PEP) carboxylase.

Cyclic electron transport involves _______ and generates _______.

photosystem I; ATP

Light is needed for photosynthesis, because it

provides a source of energy for making chemical bonds.

The carbon from CO2 is

reduced during the Calvin cycle.