Mastering Biology Chp. 8 HW

PHOTOSYSTEM 2 ONLY: -oxidation of water -reduction of electron transport chain between the two photosystems PHOTOSYSTEM 1 ONLY: -reduction of NADP+ -oxidation of electron transport chain between the two photosystems BOTH PS2 AND PS1: -light absorption -reduction of primary electron acceptor [The key function of each of the two photosystems is to absorb light and convert the energy of the absorbed light into redox energy, which drives electron transport. -In PS II (the first photosystem in the sequence), P680 is oxidized (which in turn oxidizes water), and the PS II primary electron acceptor is reduced (which in turn reduces the electron transport chain between the photosystems). -In PS I, the PS I primary electron acceptor is reduced (which in turn reduces other compounds that ultimately reduce NADP+ to NADPH), and P700 is oxidized (which in turn oxidizes the electron transport chain between the photosystems).]

ENERGY INPUT REQUIRED? 1. no energy input required 2. energy input required 3. no energy input required 4. energy input required 5. no energy input required [In both PS II and PS I, light energy is used to drive a redox reaction that would not otherwise occur. In each photosystem, this redox reaction moves an electron from the special chlorophyll pair (P680 in PS II and P700 in PS I) to that photosystem's primary electron acceptor. The result in each case is a reductant (the reduced primary electron acceptor) and an oxidant (P680+ in PS II and P700+ in PS I) that are able to power the rest of the electron transfer reactions without further energy input.]

top left pink: empty bottom left: site of H+ release top right pink: site of ATP synthesis left blue: H+ pumped across membrane middle blue: empty right blue: H+ diffuses across membrane [Photosynthetic electron transport contributes to the formation of a proton (H+) gradient across the thylakoid membrane in two places. -In PS II, the oxidation of water releases protons into the thylakoid space. -Electron transport between PS II and the cytochrome complex (through Pq) pumps protons from the stroma into the thylakoid space. The resulting proton gradient is used by the ATP synthase complex to convert ADP to ATP in the stroma.]

a. sunlight b. photosynthesis c. chloroplasts d. sugar e. chlorophyll f. carbon dioxide g. cellular respiration h. mitochondria [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.]

2. Prism disperses sunlight into individual wavelengths 3. Alga's photosynthetic pigments absorb photons at specific wavelengths 4. Absorbed photons drive photosynthesis in alga 5. Alga gives off oxygen as it photosynthesizes 6. Bacteria attracted to regions of highest oxygen concentration [In this experiment, Engelmann was able to determine which wavelengths (colors) of light are most effective at driving photosynthesis. -First, Engelmann used a prism to disperse white light from the sun into the colors (wavelengths) of the visible spectrum. -Then, using a microscope, he illuminated a filament of green algae with the visible spectrum. The photosynthetic pigments in the alga absorbed some of the wavelengths of light, using the absorbed energy to drive the reactions of photosynthesis, including oxygen production. -Engelmann used his recently discovered aerotactic bacteria to determine which wavelengths of light caused the alga to photosynthesize most. Because the aerotactic bacteria were attracted to areas of highest oxygen concentration, they congregated around the regions of the alga that photosynthesized the most. -He then counted the bacteria associated with each region of the alga illuminated by the various colors of light. Engelmann found that some wavelengths of light attracted more bacteria, suggesting that these wavelengths drive more photosynthesis than others.]

-The number of bacteria clustered at each wavelength (color) was approximately proportional to the amount of oxygen being produced by that portion of the alga. - The distribution of chloroplasts within each algal cell was approximately the same. [For Engelmann to be able to draw meaningful conclusions from his experiment, he had to assume that the number of bacteria at any location on the slide was proportional to the amount of oxygen produced by the alga at that location. If this were not the case, the distribution of the bacteria around the alga would be of no use in determining the amount of photosynthesis that occurs at each wavelength. Similarly, it was necessary for Engelmann to assume that the distribution of chloroplasts among the cells in the algal filament was approximately equal. Fewer chloroplasts in one cell compared to another would mean a lower potential for oxygen production at any color. Engelmann's microscope was sufficiently powerful to see that Cladophora cells contain many small chloroplasts that were nearly uniform in their distribution within and between cells. In contrast, Engelmann did not assume that the alga absorbed the same number of photons at each wavelength. In fact, most photosynthetic pigments absorb more strongly in the red and blue parts of the spectrum and less strongly in the yellow and green parts. He also did not assume that all absorbed photons drive photosynthesis, and thus oxygen production, by the alga. In fact, all photosynthetic organisms contain some pigments that absorb photons but do not contribute to photosynthesis or oxygen production.]

-Red line higher than black line -touch around 550 nm [An action spectrum is typically plotted so that the "action" shown on the y-axis is measured with an equal number of photons at each wavelength of the visible spectrum. But our sun does not emit equal numbers of photons at each wavelength. Instead, the sun emits the most photons in the yellow part of the spectrum, with relatively fewer photons emitted in the red and violet-blue parts of the spectrum. Thus, the red and violet-blue regions of Engelmann's action spectrum were measured with fewer photons than in the yellow part of the spectrum. To correct for this, you have to consider how increasing the number of photons in the red and violet-blue parts of the spectrum--to match the emission level in the yellow part--would change the amount of oxygen produced, and thus the number of bacteria that accumulated, in the red and violet-blue spectral regions. The corrected action spectrum would show higher peaks in the red and violet-blue parts of the spectrum, but the plot in the yellow part of the spectrum would be approximately the same as Engelmann's.]

435 nm

455 nm

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

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

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.

INPUT: -light -water -NADP+ -ADP OUTPUT: -O2 -ATP -NADPH NOT INPUT OR OUTPUT: -glucose -CO2 -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.]

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.]

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. [In the light reactions, light energy is used to remove electrons from (oxidize) water, producing O2 gas. These electrons are ultimately used to reduce NADP+ to NADPH. In the Calvin cycle, NADPH is oxidized back to NADP+ (which returns to the light reactions). The electrons released by the oxidation of NADPH are used to reduce three molecules of CO2 to sugar (G3P), which then exits the Calvin cycle.]

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.]

a) 3 molecules 3 carbons b) 6 molecules 18 carbons c) 6 molecules 18 carbons d) 5 molecules 15 carbons e) 3 molecules 15 carbons f) 3 molecules 15 carbons [Counting carbons—keeping track of where the carbon atoms go in each reaction—is a simple way to help understand what is happening in the Calvin cycle. -To produce 1 molecule of G3P (which contains 3 carbons), the Calvin cycle must take up 3 molecules of CO2 (1 carbon atom each). -The 3 CO2 molecules are added to 3 RuBP molecules (which contain 15 total carbon atoms), next producing 6 molecules of 3-PGA (18 total carbon atoms). -In reducing 3-PGA to G3P (Phase 2), there is no addition or removal of carbon atoms. -At the end of Phase 2, 1 of the 6 G3P molecules is output from the cycle, removing 3 of the 18 carbons. -The remaining 5 G3P molecules (15 total carbon atoms) enter Phase 3, where they are converted to 3 molecules of R5P. -Finally, the R5P is converted to RuBP without the addition or loss of carbon atoms.]

a) 6 ATP 6 ADP b) 6 NADPH 6 NADP+ c) 6pi d) 2pi e) 3 ADP 3 ATP [The Calvin cycle requires a total of 9 ATP and 6 NADPH molecules per G3P output from the cycle (per 3 CO2 fixed). -In Phase 2, six of the ATP and all of the NADPH are used in Phase 2 to convert 6 molecules of PGA to 6 molecules of G3P. Six phosphate groups are also released in Phase 2 (derived from the 6 ATP used). -In the first part of Phase 3, 5 molecules of G3P (1 phosphate group each) are converted to 3 molecules of R5P (also 1 phosphate group each). Thus there is a net release of 2 Pi. -In the second part of Phase 3, 3 ATP molecules are used to convert the 3 R5P into 3 RuBP. Note that in the entire cycle, 9 ATP are hydrolyzed to ADP; 8 of the 9 phosphate groups are released as Pi, and the ninth phosphate appears in the G3P output from the cycle.]

The rate of O2 production would decrease because the rate of ADP and NADP+ production by the Calvin cycle would decrease. [A reaction or process is dependent on another if the output of the second is an input to the first. For example, the light reactions are dependent on the Calvin cycle because the NADP+ and ADP produced by the Calvin cycle are inputs to the light reactions. Thus, if the Calvin cycle slows (because of a decrease in the amount of available CO2), the light reactions will also slow because the supply of NADP+ and ADP from the Calvin cycle would be reduced.]

concentration of CO2 in the air, in parts per million [This is the independent variable, which goes on the x-axis.]

average dry mass of one plant, in grams [This is the dependent variable, which goes on the y-axis.]

1200

100

Corn (C4) is on top decreasing between 90-80 Velvet leaf (C3) is on the bottom increasing between 30-50

doesn't quite go through all the points

As CO2 increases, the dry weight of corn decreases.

As CO2 increases, the dry weight of velvetleaf increases.

As atmospheric CO2 rises, velvetleaf weeds may grow larger and better compete with corn, reducing grain yields.

corn: 91 g; velvetleaf: 38 g

corn: 84 g; velvetleaf: 50 g

The dry mass of corn would decrease by about 8%, and the dry mass of velvetleaf would increase by about 32%.

Yes, because C3 velvetleaf had a positive growth response to increased CO2, but C4 corn had a negative growth response to it.