BSC 1010C Ch10 HW
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.
1) In the light reactions, light energy is used to oxidize H2O to O2. 2) The electrons derived from this oxidation reaction in the light reactions are used to reduce NADP+ to NADPH. 3) The Calvin cycle oxidizes the light-reactions product NADPH to NADP+. 4)The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce CO2 to G3P.
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. Diagram showing electron transport through the four major protein complexes in the thylakoid membrane of a chloroplast: Photosystem II, cytochrome complex, Photosystem I, and NADP+ reductase For each step of photosynthetic electron flow from water to NADP+, drag the appropriate label to indicate whether or not that step requires an input of energy.
1. Water --> P680+ (No energy input required) 2. P680 --> Pq (pastoquinone) (energy input required) 3. Pq ---> P700+ (No energy input required) 4. P700 ---> Fd (ferredoxin) (energy input required) 5. Fd ---> NADP+ (No energy input required)
Proton gradient formation and ATP synthesis ATP synthesis in chloroplasts is very similar to that in mitochondria: Electron transport is coupled to the formation of a proton (H+) gradient across a membrane. The energy in this proton gradient is then used to power ATP synthesis. Two types of processes that contribute to the formation of the proton gradient are: processes that release H+ from compounds that contain hydrogen, and processes that transport H+ across the thylakoid membrane. Drag the labels to the appropriate locations on the diagram of the thylakoid membrane. Use only the blue labels for the blue targets, and only the pink labels for the pink targets. Note: One blue target and one pink target should be left empty.
Bottom Left Red Box: Site of H+ release First Blue Box: H+ pumped across membrane Third/Last Blue Box: H+ diffuse across membrane Last red box (at the top right) : site of ATP synthesis
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.
Input: NADP+, ADP, water, light Output: ATP, NADPH, O2 Not input or output: CO2, G3P, glucose
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.
Input: NADPH, ATP, CO2 Output: ADP, NADP+, G3P Not input or output: O2, glucose, light
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.
Photosystem II (PS II) only : oxidation of water, reduction of electron transport chain between the two photosystems Photosystem I (PS I) only: reduction of NADP+ , oxidation of electron transport chain between the two photosystems both PS II and PS I: light absorption, reduction of primary electron acceptor
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.)
The rate of O2 production would decrease because the rate of ADP and NADP+ production by the Calvin cycle would decrease.
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.
a. 3 molecules 3 carbon b. 6 molecules 18 carbon c. 6 molecules 18 carbon d. 5 molecules 15 carbon e. 3 molecules 15 carbon f. 3 molecules 15 carbon
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.
a. 6ATP 6 ADP B. 6 NADPH 6 NADP+ C. 6Pi D. 2P E. 3 ADP 3 ATP
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.
a. stroma b. thylakoid membrane c. cytosol d. location of Calvin cycle e. thylakoid space f. location of light reactions g. envelope membranes
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.
a. sunlight b. photosynthesis c. chloroplasts d. sugar e. chlorophyll f. carbon dioxide g. cellular respiration h. mitochondria
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.
cytoplasm
In C3 plants the conservation of water promotes _____.
photorespiration
C4 plants differ from C3 and CAM plants in that C4 plants _____.
transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
