Mastering Biology CH 10
What are the products of linear electron flow in the light reactions of photosynthesis?
ATP and NADPH
The light reactions supply the Calvin cycle with
ATPATP and NADPHNADPH.
Which of the following is a true statement?
Anabolic pathways build molecules, require energy, and are endergonic.
_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
B
Select the correct molecule that is the main product of the Calvin cycle.
G3P
Why are plants classified as producers?
Plants are classified as producers because they fix inorganic carbon into organic molecules.
When a pigment molecule in a light-harvesting complex absorbs a photon of light, what happens to its excited-state electron?
The electron falls back to its ground state, while passing its excited-state energy to an electron in a nearby pigment molecule.
A mutation that eliminates a plant's ability to perform photorespiration will most likely have which of the following effects on the plant?
There would be more cellular damage from harmful products of the light reactions of photosynthesis.
What is the biological significance of the light-independent reactions of photosynthesis?
They convert carbon dioxide to sugar.
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 oxidation of water reduction of electron transport chain between the two photosystems- Photosystem I reduction of NADP+oxidation of electron transport chain between the two photosystems- Both light absorption reduction of primary electron acceptor
How many electrons at a time are passed between the pigment molecules in the light-harvesting complexes?
0
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.
For every molecule of O2 that is released by photosystem II, _________ H2O molecules are needed, which together pass _________ electrons to the PS II reaction-center complex.
2,4
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6
If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), which of the following molecules produced by the algae (refer to the accompanying figure) would be least likely to contain 18O in subsequent analyses?
ADP
Which of the following statements best summarizes the metabolic results of photorespiration?
ATP is hydrolyzed, carbon dioxide is produced, and oxygen is consumed
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?
ATP will not be produced because there is no ADP and inorganic phosphate in the solution.
Which of the following statements best explains why photosynthesis using C4 or CAM systems may be described as a metabolic compromise?
Both pathways minimize photorespiration but also expend more ATP in the process of carbon fixation.
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells
Cytoplasm
Why is it correct to say that the linear electron flow of the light reactions directly captures energy in NADPH but only indirectly captures energy in ATP?
Electrons are directly transferred to NADP+ to form NADPH, but electron flow is used to generate a proton gradient for ATP synthesis. Electrons are not directly transferred to ATP.
What happens along an electron transport chain?
Electrons are passed from a reducing agent to an oxidizing agent, releasing free energy at each step.
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.
False
True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.
False
Which of the following is the correct order of electron flow in the light reactions of photosynthesis?
H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → NADPH
How is photosynthesis similar in C4C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially.
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: light, water, NADP+, ADP Output: O2, ATP, NADPH not input or output: glucose, CO2,G3P
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:ATP, NADPH, CO2 Output:ADP, NADP+, G3P not input or output:light, glucose, O2
A flask containing photosynthetic green algae and a control flask containing only water are exposed to a cycle of 12 hours of light and 12 hours of darkness. Which of the following statements best describes how the relative dissolved oxygen concentration in the flask with algae will compare to the control flask?
It will be lower in the control in the light, but higher in the control in the dark.
After 3-PGA is phosphorylated, it is reduced by _____.
NADPH
Which of the following molecules is the primary reducing agent in the Calvin cycle reactions?
NADPH
If the Calvin cycle slows down, what will happen to the rate of O2 production in PS II, and why?
O2 production will slow down because less NADP+ will be regenerated in the Calvin cycle.
_____ has a longer wavelength than _____.
Red ... green
To identify the molecule that first reacts with CO2 in the light-independent reactions of photosynthesis, Calvin and Benson manipulated the carbon-fixation cycle by either elminating CO2 or light from cultures of photosynthetic algae. Which of the following statements best predicts the immediate effects of these manipulations on the concentration of the molecule that initially reacts with CO2?
The concentration would increase when the CO2 is eliminated, but decrease when the light is eliminated.
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.
Which of the following events are associated with chemiosmosis in chloroplasts?
The pH of the thylakoid space increases and ATP is synthesized.
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.
Which of the following statements best explains the ability of CAM plants to synthesize sugars in the daytime while keeping their stomata closed to reduce water loss?
They fix CO2 into organic acids during the night.
Which of the following statements best explains the ability of C4 plants to perform photosynthesis with no apparent photorespiration?
They use PEP carboxylase to initially fix CO2.
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
a) stroma- b) thylakoid membrane- c)cytosol- d) location of Calvin Cycle- e) thylakoid space- f)location of light reactions- g) envelope membranes-
Following carbon atoms around the Calvin cycleThe 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 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
Which of the following processes is driven by the free energy released as electrons move through photosystem II and I in the thylakoid membranes?
establishment of a proton gradient
Which set of reactions uses H2O and produces O2?
light dependent
Which of the following processes is most directly driven by light energy?
oxidation of chlorophyll molecules
The mechanism of photophosphorylation is most similar to which of the following processes?
oxidative phosphorylation in cellular respiration
In mechanism, photophosphorylation is most similar to
oxidative phosphorylation in cellular respiration.
Which of the following is(are) produced by the light reactions of photosynthesis?
oxygen, ATP, and NADPH
In C3 plants the conservation of water promotes _____.
photorespiration
ATP is synthesized in plant cells by chemiosmosis in which of the following processes?
photosynthesis and cellular respiration
Which of the following processes is directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
Which of the following processes occurs in the Calvin cycle?
reduction of CO2
Which of the following processes would be most directly affected if a thylakoid membrane is punctured so that the interior of the thylakoid is no longer separated from the stroma?
synthesis of ATP
C4 plants occur more commonly in desert conditions because __________.
they can fix carbon at the lower CO2 concentrations that develop when the stomata are fully or partially closed
If various plant cell membranes are isolated and incubated with a proton gradient across the isolated membrane in the presence of ADP and Pi, which of the following samples are most likely to be able to synthesize ATP?
thylakoid membrane and inner mitochondrial membrane
C4 plants differ from C3 and CAM plants in that C4 plants _____.
transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
When a filament of algae is illuminated with light that is passed through a prism, different segments of algae are exposed to different wavelengths of light. When aerobic bacteria are present, they congregate in highest concentrations in the areas illuminated by the red and blue light. These data suggest a relationship between which of the following variables?
wavelength of light and the rate of photosynthesis
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.
1. no energy input required 2. energy input required 3. no energy input required 4. energy input required 5. no energy input required
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
3
