Mastering Biology Chapter 10

Sentences summarizing the redox reactions of photosynthesis: In the light reactions, light energy is used to oxidize _____ to _______

H2O...........O2

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 to P680+ 2) P680 to Pq (plastoquinone) 3) Pq to P700+ 4) P700 to Fd (ferredoxin) 5) Fd to NADP+

1. No energy input recquired 2. Energy input required 3. No energy input required 4. Energy input required 5. No energy input required

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

Cytoplasm

Sentences summarizing the redox reactions of photosynthesis: The electrons derived from the oxidation reaction in the light reactions are used to reduce _______ to ________

NADP+.......NADPH

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

Photorespiration

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

Transfer fixed carbon dioxide to cells in which the Calvin cycle occurs

Sentences summarizing the redox reactions of photosynthesis: The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce ______ to _____

CO2.........G3P

Separate each item into one of the three categories, Photosystem II (PS II) only, Photosystem I (PS I) only, or both PS II and PS I. 1. Reduction of NADP+ 2. Reduction of primary electron acceptor 3. Oxidation of water 4. Light absorbtion 5. Reduction of electron transport chain between the two photosystems 6. Oxidation of electron transport chain between the two photosystems

1. Photosystem I 2. Both Photosystem I and Photosystem 2 3. Photosystem 2 4. Both Photosystem I and Photosystem 2 5. Photosystem 2 6. Photosystem 1

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. Choose between light, glucose, CO2, NADPH, G3P, NADP+, O2, ADP, and ATP

Input: ATP, NADPH, CO2 Output: ADP, NADP+, G3P Not input or output: light, glucose, O2 In the Calvin cycle, the energy outputs from the light reactions (ATP and NADPH) are used to power the conversion of CO2 into the sugar G3P. As ATP and NADPH are used, they produce ADP and NADP+, respectively, which are returned to the light reactions so that more ATP and NADPH can be formed.

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.) Choices are-light, water, ATP, ADP, NADP+, NADPH, O2, CO2, glucose, and G3P

Input: Light, water, NADP+, and ADP Output: O2 ATP, and NADPH Neither Input or Output: CO2, glucose, and G3P In the light reactions, the energy of sunlight is used to oxidize water (the electron donor) to O2 and pass these electrons to NADP+, producing NADPH. Some light energy is used to convert ADP to ATP. The NADPH and ATP produced are subsequently used to power the sugar-producing Calvin cycle.

Sentences summarizing the redox reactions of photosynthesis: The Calvin cycle oxidizes the light reactions product _____ to ______

NADPH......NADP+

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. The rate of O2 production would remain the same because the light reactions are independent of the Calvin cycle. The rate of O2 production would remain the same because the light intensity did not change. The rate of O2 production would decrease because the rate of G3P production by the Calvin cycle would decrease.

The rate of O2 production would decrease because the rate of ADP and NADP+ production by the Calvin cycle would decrease

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.

a) stroma- the dense fluid surrounded between the inner envelope membrane and the thylakoid membranes b) thylakoid membrane- the third membrane system; surrounds the thylakoid; chrorophyll resides in the thylakoid membrane c)cytosol- the fluid portion of cytoplasm surrounding (outside) the chloroplast d) location of Calvin Cycle- the calvin cycle occurs in the stroma e) thylakoid space- the space within the thylakoid sacs f)location of light reactions- the light reactions occur in the thylakoids of the chloroplast g) envelope membranes- the inner and outer membranes of the chloroplast The chloroplast is enclosed by a pair of envelope membranes (inner and outer) that separate the interior of the chloroplast from the surrounding cytosol of the cell. Inside the chloroplast, the chlorophyll-containing thylakoid membranes are the site of the light reactions. Between the inner envelope membrane and the thylakoid membranes is the aqueous stroma, which is the location of the reactions of the Calvin cycle. Inside the thylakoid membranes is the thylakoid space, where protons accumulate during ATP synthesis in the light reactions.