BIO181 Chapter 10 MasteringBiology Homework

Part A - Photosynthesis and respiration in plants Drag the labels from the left to their correct locations in the concept map on the right. Not all labels will be used.

Part A - Inputs and outputs of the light reactions From the following choices, identify those that are the inputs and outputs of the light reactions. (Recall that inputs to chemical reactions are modified over the course of the reaction as they are converted into products. In other words, if something is required for a reaction to occur, and it does not remain in its original form when the reaction is complete, it is an input.) Drag each item to the appropriate bin. If the item is not an input to or an output from the light reactions, drag it to the "not input or output" bin.

Part B - Inputs and outputs of the Calvin cycle From the following choices, identify those that are the inputs and outputs of the Calvin cycle. Drag each item to the appropriate bin. If the item is not an input to or an output from the Calvin cycle, drag it to the "not input or output" bin.

Part C - Redox reactions of photosynthesis In photosynthesis, a redox compound that is produced in the light reactions is required to drive other redox reactions in the Calvin cycle, as shown in this figure along with other components of photosynthesis. Drag the terms to the appropriate blanks to complete the following sentences summarizing the redox reactions of photosynthesis. Terms may be used once, more than once, or not at all

Part D - Chloroplast structure and function In eukaryotes, all the reactions of photosynthesis occur in various membranes and compartments of the chloroplast. Identify the membranes or compartments of the chloroplast by dragging the blue labels to the blue targets. Then, identify where the light reactions and Calvin cycle occur by dragging the pink labels to the pink targets. Note that only blue labels should be placed in blue targets, and only pink labels should be placed in pink targets.

Part A - Functions of the photosystems The light reactions require the cooperation of two photosystems to power linear electron flow from water to NADP+. Drag each item into the appropriate bin depending on whether the process is associated with Photosystem II (PS II) only, Photosystem I (PS I) only, or both PS II and PS I. Note that "electron transport chain" here refers to the electron transport chain between the two photosystems, not the one that functions after PS I.

Part B - Energetics of electron transport This diagram shows the basic pattern of electron transport through the four major protein complexes in the thylakoid membrane of a chloroplast.

Part C - Proton gradient formation and ATP synthesis

Part A - Following carbon atoms around the Calvin cycle The net reaction of the Calvin cycle is the conversion of CO2 into the three-carbon sugar G3P. Along the way, reactions rearrange carbon atoms among intermediate compounds and use the ATP and NADPH produced by the light reactions. In this exercise, you will track carbon atoms through the Calvin cycle as required for the net production of one molecule of G3P. For each intermediate compound in the Calvin cycle, identify the number of molecules of that intermediate and the total number of carbon atoms contained in those molecules. As an example, the output G3P is labeled for you: 1 molecule with a total of 3 carbon atoms. Labels may be used once, more than once, or not at all.

Part B - Quantifying the inputs of ATP and NADPH and output of Pi The Calvin cycle depends on inputs of chemical energy (ATP) and reductant (NADPH) from the light reactions to power the conversion of CO2 into G3P. In this exercise, consider the net conversion of 3 molecules of CO2 into 1 molecule of G3P. Drag the labels to the appropriate targets to indicate the numbers of molecules of ATP/ADP, NADPH/NADP+, and Pi (inorganic phosphate groups) that are input to or output from the Calvin cycle. Labels can be used once, more than once, or not at all.

Part C - Do the light reactions of photosynthesis depend on the Calvin cycle? The rate of O2 production by the light reactions varies with the intensity of light because light is required as the energy source for O2 formation. Thus, lower light levels generally mean a lower rate of O2 production. In addition, lower light levels also affect the rate of CO2 uptake by the Calvin cycle. This is because the Calvin cycle needs the ATP and NADPH produced by the light reactions. In this way, the Calvin cycle depends on the light reactions. But is the inverse true as well? Do the light reactions depend on the Calvin cycle? Suppose that the concentration of CO2 available for the Calvin cycle decreased by 50% (because the stomata closed to conserve water). Which statement correctly describes how O2 production would be affected? (Assume that the light intensity does not change.)

Part A In C3 plants the conservation of water promotes _____. the light reactions the opening of stomata a shift to C4 photosynthesis photorespiration photosynthesis

Part B In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells. thylakoids grana cytoplasm stomata stroma

Part C C4 plants differ from C3 and CAM plants in that C4 plants _____. use PEP carboxylase to fix carbon dioxide use malic acid to transfer carbon dioxide to the Calvin cycle are better adapted to wet conditions open their stomata only at night transfer fixed carbon dioxide to cells in which the Calvin cycle occur

Part A Which of these equations best summarizes photosynthesis? H2O → 2 H+ + 1/2 O2 + 2e- C6H12O6 + 6 O2 → 6 CO2 + 12 H2O 6 CO2 + 6 H2O → C6H12O6 + 6 O2 6 CO2 + 6 O2 → C6H12O6 + 6 H2O C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

Part B here does the Calvin cycle occur? B C E D A

Part C The light reactions of photosynthesis use _____ and produce _____. NADPH ... NADP+ NADPH ... oxygen water ... NADPH carbon dioxide ... oxygen carbon dioxide ... sugar

Part A Identify the chloroplast. E D B C A

Part B Identify the stroma. D E A B C

Part C Identify a thylakoid. B C A D E

Part A Which term describes ATP production resulting from the capture of light energy by chlorophyll? Substrate-level phosphorylation Photophosphorylation Dephosphorylation Oxidative phosphorylation

Part B 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.

Part C According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis? Osmotic gradient Electrons Proton gradient Temperature gradient

Part D Which of the following particles can pass through the ATP synthase channel? Inorganic phosphate ATP ADP Protons

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

Part F 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? 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. ATP will be produced because the proton gradient favors proton movement through the ATP synthase channels. ATP will not be produced because there is no ADP and inorganic phosphate in the solution. Protons will not diffuse toward the outside of the vesicles.

Part A _____ has a longer wavelength than _____. Red ... green Blue ... green Green ... yellow Yellow ... red Violet ... blue

Part A Which of these phosphorylates ADP to make ATP? A E B D C

Part B _____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment. D C E A B

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

Part D Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+. D B C E A

Part E Chlorophyll can be found in _____. A and B B and C B and D B and E A and C

Part A In Engelmann's experiment, he used aerotactic (oxygen-seeking) bacteria to determine which wavelengths of visible light were most effective in driving the reactions of photosynthesis in green algae. A diagram of his apparatus is shown below. Can you deduce the logical link between light of different wavelengths and the distribution of bacteria that Engelmann observed? Drag the labels onto the flowchart to show the relationship between the production of photons by the sun (Engelmann's light source) and the distribution of bacteria that Engelmann observed under his microscope. Not all labels will be used.

Part B Engelmann counted the number of bacteria that were attracted to the algal filament associated with each color of light. As shown in the image below, most of the bacteria were attracted to the regions of the alga illuminated by red or violet-blue light. This distribution of bacteria shows that red and violet-blue wavelengths are most effective in driving photosynthesis. By measuring oxygen production with aerotactic bacteria, Engelmann described an action spectrum for photosynthesis. The action spectrum (indicated by the black line plot in the image above) shows the relative effectiveness of each color of light in driving photosynthesis. What assumptions did Engelmann make in order to conclude that red and violet-blue light were more effective than green light in driving photosynthesis? Select the two that apply. What assumptions did Engelmann make in order to conclude that red and violet-blue light were more effective than green light in driving photosynthesis? Select the two that apply.

Part C One of the assumptions that Engelmann made was that the sun (his light source) emits equal numbers of photons at each wavelength in the visible spectrum. In reality, the sun's emission peaks in the yellow region of the spectrum, with relatively fewer photons emitted in the red and violet-blue regions. Recall that the action spectrum from Engelmann's experiment plotted the rate of photosynthesis (as measured by oxygen production) versus wavelength. In each of the following graphs, the black line shows Engelmann's original action spectrum deduced from the distribution of aerotactic bacteria around the alga. Which red line shows the same action spectrum corrected for the unequal number of photons emitted across the visible spectrum?

Part A Which process produces oxygen? Photosynthesis Cellular respiration

Part B Which set of reactions uses H2O and produces O2? The light-independent reactions The light-dependent reactions

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

Part D True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

Part E Which of the following molecules is the primary product of photosystem I? NADPH ATP Carbon dioxide Oxygen

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

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

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

Part A Carbon fixation involves the addition of carbon dioxide to _____. 3-PGA NADPH RuBP G3P Rubisco

Part B After 3-PGA is phosphorylated, it is reduced by _____. ADP ATP NADPH NADP+ CO2

Part C How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose? 6 2 4 10 8

Part D In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules? 3 4 5 1 2

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

Part B Which wavelength of light is best absorbed by chlorophyll b? 400 nm 455 nm 540 nm 645 nm One cannot tell from this graph.

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

Part D Can you tell from these absorption spectra whether red light is effective in driving photosynthesis? These absorption spectra indicate that green and yellow wavelengths of light are much more effective than red light. 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. Because the absorption spectra of the pigments are highest in the purple/blue wavelengths, we can assume that red light is not effective.

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

Part F 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? 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. 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. 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.