Mastering Biology Chapter 10 Pre-Lecture Assignment

Photosynthesis and respiration in plants:

A mutually dependent relationship exists between chloroplasts and mitochondria in the plant cell. Photosynthesis, which occurs in chloroplasts, generates the sugars and oxygen gas that are used in mitochondria for cellular respiration. Cellular respiration generates carbon dioxide, which in turn is used as a carbon source for the synthesis of sugars during photosynthesis. Cellular respiration also generates ATP and water, which are used in various chemical reactions in the plant cell.

_____ splits water into 1/2 O2, H+, and e- . a. E b. C c. A d. B e. D

c. A Photosystem II splits water into 1/2 O2, H+, and e- .

Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions? a. 435 nm b. 525 nm c. 680 nm d. One cannot tell from this graph.

a. 435 nm

Chlorophyll can be found in _____. a. A and C b. B and D c. B and C d. B and E e. A and B

a. A and C The photosystems contain chlorophyll.

Which of these phosphorylates ADP to make ATP? a. E b. C c. D d. A e. B

a. E ATP synthase phosphorylates ADP.

Where does the Calvin cycle occur? a. E b. B c. A d. D e. C

a. E The Calvin cycle occurs in the stroma.

Which term describes ATP production resulting from the capture of light energy by chlorophyll? a. Photophosphorylation b. Substrate-level phosphorylation c. Dephosphorylation d. Oxidative phosphorylation

a. Photophosphorylation The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production.

Which of the following particles can pass through the ATP synthase channel? a. Protons b. ADP c. ATP d. Inorganic phosphate

a. Protons The channels formed by ATP synthase are specific for protons.

Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose? a. Regneration of RuBP b. Production of 3-phosphoglycerate c. Production of G3P d. Carbon fixation

a. Regneration of RuBP The regeneration of RuBP ensures that the Calvin cycle can proceed indefinitely, since RuBP fixes carbon dioxide into an organic molecule that is used to produce sugar.

If only chlorophyll a were involved in the light reactions, would blue light (wavelength about 490 nm) be effective in driving photosynthesis? a. The graph indicates that chlorophyll a absorbs very little blue light, so we can predict that blue light would not be effective. b. One cannot tell from this graph. c. The peak absorption for chlorophyll b is close to this wavelength, so we can predict that blue light would be effective.

a. The graph indicates that chlorophyll a absorbs very little blue light, so we can predict that blue light would not be effective.

What is the biological significance of the light-independent reactions of photosynthesis? a. They convert carbon dioxide to sugar. b. They make oxygen. c. They generate ATP and NADPH. d. They convert ATP to sugar.

a. They convert carbon dioxide to sugar. All organisms use the sugars produced by photosynthesis to generate energy.

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen. a. True b. False

a. True The water molecules are split to replenish electrons in photosystem II, leaving behind protons, which are used to generate a proton gradient for the formation of ATP, and oxygen, which is released as a by-product.

Which wavelength of light is best absorbed by chlorophyll b? a. 400 nm b. 455 nm c. 540 nm d. 645 nm e. One cannot tell from this graph.

b. 455 nm

True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain. a. True b. False

b. False The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane. a. True b. False

b. False The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.

Which of the following molecules is the primary product of photosystem I? a. ATP b. NADPH c. Oxygen d. Carbon dioxide

b. NADPH The NADPH produced by photosystem I is used to supply energy for the production of sugars during photosynthesis.

Which process produces oxygen? a. Cellular respiration b. Photosynthesis

b. Photosynthesis Oxygen is a by-product of the photosynthetic process.

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis? a. Osmotic gradient b. Proton gradient c. Temperature gradient d. Electrons

b. Proton gradient A proton gradient across chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase.

Which set of reactions uses H2O and produces O2? a. The light-independent reactions b. The light-dependent reactions

b. The light-dependent reactions The light-dependent reactions use H2O and produce O2.

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis? a. The light-dependent reactions pass electrons through an electron transport chain to the light-independent reactions. b. The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions. c. The light-independent reactions release energy, and the light-dependent reactions require energy. d. The light-dependent reactions produce carbon dioxide, which is then used by the light-independent reactions.

b. The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions. Light energy drives the formation of ATP and NADPH during the light-dependent reactions; these energy molecules are then used during the light-independent reactions to form sugars.

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere? a. The light-independent reactions turn sugar into ATP for energy. b. The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars. c. The light-independent reactions turn glucose, a sugar, into CO2 gas. d. The light-independent reactions use CO2 to make ATP.

b. The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars. CO2 is unusable until plants have "fixed" this carbon into sugar.

Which of these equations best summarizes photosynthesis? a. H2O → 2 H+ + 1/2 O2 + 2e- b. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy c. 6 CO2 + 6 H2O → C6H12O6 + 6 O2 d. 6 CO2 + 6 O2 → C6H12O6 + 6 H2O e. C6H12O6 + 6 O2 → 6 CO2 + 12 H2O

c. 6 CO2 + 6 H2O → C6H12O6 + 6 O2 This is the equation that summarizes the reactions of photosynthesis.

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5. The solution is then adjusted to pH 8. Which of the following conclusions can be drawn from these experimental conditions? a. Protons will not diffuse toward the outside of the vesicles. b. The change in the solution's pH results in a gradient across the chloroplast membranes such that there is a lower concentration of protons inside the vesicles and a higher concentration outside. c. ATP will not be produced because there is no ADP and inorganic phosphate in the solution. d. ATP will be produced because the proton gradient favors proton movement through the ATP synthase channels.

c. ATP will not be produced because there is no ADP and inorganic phosphate in the solution. This statement is true; although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added to the reaction.

Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+. a. E b. A c. C d. B e. D

c. C Energized electrons from photosystem I are used to reduce NADP+.

Can you tell from these absorption spectra whether red light is effective in driving photosynthesis? a. These absorption spectra indicate that green and yellow wavelengths of light are much more effective than red light. b. Because the absorption spectra of the pigments are highest in the purple/blue wavelengths, we can assume that red light is not effective. c. One cannot tell from this graph, but because chlorophyll a does absorb red light, we can predict that it would be effective in driving photosynthesis.

c. One cannot tell from this graph, but because chlorophyll a does absorb red light, we can predict that it would be effective in driving photosynthesis.

An action spectrum plots the rate of photosynthesis at various wavelengths of visible light, and it shows that blue light with a wavelength of about 490 nm is effective in driving photosynthesis. Based on this information and the absorption spectra shown at left, what role may chlorophyll b and carotenoids play in photosynthesis? a. These pigments probably play only a photoprotective role (absorbing excess light energy that could damage chlorophyll a) and a role in producing the colors of fall foliage. b. Because chlorophyll a is found in the reaction-center complexes of both photosystems II and I, we can assume that these other pigments play no role in photosynthesis. c. These pigments are able to absorb more wavelengths of light (and thus more energy) than chlorophyll a alone can absorb. As part of light-harvesting complexes in photosystems, they broaden the range of light that can be used in the light reactions.

c. These pigments are able to absorb more wavelengths of light (and thus more energy) than chlorophyll a alone can absorb. As part of light-harvesting complexes in photosystems, they broaden the range of light that can be used in the light reactions.

You obtain the pigments called carotenoids in your diet when you eat carrots. Why do carotenoids appear yellow and orange? a. Their line on this absorption spectrum is colored orange. b. They absorb yellow and orange wavelengths best. c. One cannot tell from this graph. d. They absorb blue/green light and reflect yellow and red wavelengths of light.

d. They absorb blue/green light and reflect yellow and red wavelengths of light.

_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment. a. C b. E c. D d. A e. B

e. B The energy released as electrons are passed along the electron transport chain is used to pump protons into the thylakoid compartment.

The light reactions of photosynthesis use _____ and produce _____. a. NADPH ... NADP+ b. carbon dioxide ... sugar c. NADPH ... oxygen d. carbon dioxide ... oxygen e. water ... NADPH

e. water ... NADPH NADPH is a reactant in the Calvin cycle.