The light reactions of photosynthesis supply the Calvin cycle with
ATP and NADPH.
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
H2O ? NADPH ? Calvin cycle
How is photosynthesis similar in C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially.
Which of the following statements is a correct distinction between autotrophs and heterotrophs?
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.

Which of the following does not occur during the Calvin cycle?
release of oxygen
In mechanism, photophosphorylation is most similar to
oxidative phosphorylation in cellular respiration.
Which process is most directly driven by light energy?
removal of electrons from chlorophyll molecules
Select the most accurate statement describing the basic function of the light reactions of photosynthesis.
The basic function of the light reactions of photosynthesis is the conversion of solar energy to chemical energy.
Select the correct molecule that is the main product of the Calvin cycle.
G3P
What is the basic role of CO2 in photosynthesis?
CO2 is fixed or incorporated into organic molecules.
Select the correct statement about the Calvin cycle.

The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.
Why are plants classified as producers?
Plants are classified as producers because they fix inorganic carbon into organic molecules.
Which of the following is generally true about the stratosphere?
It is very dry.
Based on current findings, which of the following is true?
As climate change speeds up, there will be an increase in the number of strong storms, in turn causing an increased amount of ozone depletion.

Where was the thinning of ozone initially discovered?
Over the Antarctic
You are the CEO of a major manufacturing company that decides to use CFCs in production of your products. What are you failing to abide by?
Montreal Protocol
Which of the following two things worked in conjunction to make CFCs harmful to the ozone?
chlorine and sunlight
Identify the chloroplast.
A
Identify the stroma.
E
Identify a thylakoid.
D
Which of these equations best summarizes photosynthesis?
6 CO2 + 6 H2O ? C6H12O6 + 6 O2
Where does the Calvin cycle occur?
E
The light reactions of photosynthesis use _____ and produce _____.

water ... NADPH
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.

a. sunlight b. photosynthesis c. chloroplasts d. sugar e.

chlorophyll f. carbon dioxide g. cellular respiration h. mitochondria

Plants are photoautotrophs. What does this mean?
They use light energy to drive the synthesis of organic molecules from inorganic materials.

The ultimate source of energy to support most life on Earth is _____.
sunlight
The photosynthetic membranes are found in the _____ in plant cells.
chloroplasts
The process of photosynthesis probably originated _____.
in prokaryotes
In autotrophic bacteria, where is chlorophyll located?
in the infolded plasma membrane
Plants photosynthesize _____.
only in the light but respire in light and dark
Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide.

In fact, it comes from _____.

water
If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), later analysis will show that all of the following molecules produced by the algae contain 18O EXCEPT _____.
O2
Every ecosystem must have _____.
autotrophs
When oxygen is released as a result of photosynthesis, it is a direct by-product of _____.

splitting water molecules
Use your knowledge of the mechanism of photosynthesis and the data presented in the chart to determine which of the statements below is a correct explanation for the student's data.
Cup 4 had the slowest rate of photosynthesis because it had the least baking soda.
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.

*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).
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.
no energy energy no energy energy no energy
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.

*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.

Diagram showing the organization of the thylakoid membrane

_____ has a longer wavelength than _____.
Red ...

green

Which of these phosphorylates ADP to make ATP?
C
_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
B
_____ splits water into 1/2 O2, H+, and e- .
A
Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.
C
Chlorophyll can be found in _____.
A and C
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.

*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.

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.
The distribution of chloroplasts within each algal cell was approximately the same.

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.

Which red line shows the same action spectrum corrected for the unequal number of photons emitted across the visible spectrum?
*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.

Which term describes ATP production resulting from the capture of light energy by chlorophyll?
Photophosphorylation
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
According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?
Proton gradient
Which of the following particles can pass through the ATP synthase channel?
Protons
True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

False
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?
In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____.
ultraviolet radiation and infrared radiation
Which of the following is a product of the light reactions of photosynthesis?
oxygen, ATP, and NADPH
When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____.
splitting water
Photosynthesis is a redox reaction. This means that H2O is _____ during the light reactions and CO2 is _____ during the Calvin cycle.

oxidized...reduced
Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions?
435 nm
Which wavelength of light is best absorbed by chlorophyll b?
455 nm
You obtain the pigments called carotenoids in your diet when you eat carrots. Why do carotenoids appear yellow and orange?
They absorb blue/green light and reflect yellow and red wavelengths of light.

Can you tell from these absorption spectra whether red light is effective in driving photosynthesis?
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.
If only chlorophyll a were involved in the light reactions, would blue light (wavelength about 490 nm) 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.
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 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.

Which wavelengths of light drive the highest rates of photosynthesis? Select the two best answers.
400-450 nm 670-680 nm
The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?
Other pigments absorb light in addition to chlorophyll a.

What wavelength of light in the figure is most effective in driving photosynthesis?
420 mm
Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He noted that the largest groups were found in the areas illuminated by the red and blue light. What did Engelmann conclude about the congregation of bacteria in the red and blue areas?
Bacteria congregated in these areas because these areas had the most oxygen being released.
An outcome of Engelmann's experiment was to help determine the relationship between _____.

wavelengths of light and the rate of photosynthesis
What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?
a mixture of blue and red light
Suppose a plant has a unique photosynthetic pigment and the leaves of this plant appear to be reddish yellow. What wavelengths of visible light are absorbed by this pigment?
blue and violet
Halobacterium has a photosynthetic membrane that appears purple. Its photosynthetic action spectrum is the inverse of the action spectrum for green plants. (That is, the Halobacterium action spectrum has a peak where the green plant action spectrum has a trough.

) What wavelengths of light do the Halobacterium photosynthetic pigments absorb?

green and yellow
Why are there several structurally different pigments in the reaction centers of photosystems?
This arrangement enables the plant to absorb light energy of a variety of wavelengths.
If pigments from a particular species of plant are extracted and subjected to paper chromatography, which of the following is most likely?
Paper chromatography would separate the pigments from a particular plant into several bands.
In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and _____.
carotenoids and other pigments are still present in the leaves
What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?
An electron is excited.
As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy.

What happens to this energy?

It is used to establish and maintain a proton gradient.
The final electron acceptor associated with photosystem I is _____.
NADP
The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?
water
In the thylakoid membranes, the pigment molecules in a light-harvesting complex _____.
absorb and transfer light energy to the reaction-center chlorophyll
Which of the following are directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive.

The best way to detect the lack of photosystem II in these organisms would be to _____.

test for liberation of O2 in the light
What are the products of linear electron flow?
ATP and NADPH
As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find that 30,000 molecules of ATP were consumed, but only 20,000 molecules of NADPH were consumed. Where did the extra ATP molecules come from?
cyclic electron flow
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma.

This damage will most directly affect the _____.

synthesis of ATP
In a plant cell, where are the ATP synthase complexes located?
thylakoid membrane and inner mitochondrial membrane
In mitochondria, chemiosmosis moves protons from the intermembrane space into the matrix, whereas in chloroplasts, chemiosmosis moves protons from the _____.
thylakoid space to the stroma
Which of the following statements best describes the relationship between photosynthesis and respiration?
Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules
In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during _____.
photosynthesis and respiration
Carbon dioxide is split to form oxygen gas and carbon compounds _____.
in neither photosynthesis nor respiration
What is the relationship between the wavelength of light and the quantity of energy per photon?
They are inversely related.

P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?
It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.
Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?
They protect against oxidative damage from excessive light energy.
In a plant, the reactions that produce molecular oxygen (O2) take place in _____.
the light reactions alone
The accumulation of free oxygen in Earth's atmosphere began with the origin of _____.

cyanobacteria using photosystem II
In its mechanism, photophosphorylation is most similar to _____.
oxidative phosphorylation in cellular respiration
A gardener is concerned that her greenhouse is getting too hot from too much light and seeks to shade her plants with colored translucent plastic sheets, the color of which allows passage of only that wavelength. What color should she use to reduce overall light energy but still maximize plant growth?
blue
A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask. The dissolved oxygen in the flask with algae will _____.

be higher in the light, but lower in the dark
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.
*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.

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.
*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.

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.
*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.

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.

*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.
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.

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 The G3Ps are used in Phase 3 to regenerate the RuBP molecules used in Phase 1.

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.

*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.

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.
Carbon fixation involves the addition of carbon dioxide to _____.
RuBP
After 3-PGA is phosphorylated, it is reduced by _____.
NADPH
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
3
Which process produces oxygen?
Photosynthesis
Which set of reactions uses H2O and produces O2?
The light-dependent reactions
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.
True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.
True
Which of the following molecules is the primary product of photosystem I?
NADPH
What is the biological significance of the light-independent reactions of photosynthesis?
They convert carbon dioxide to sugar.

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?
The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.
Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?
Regneration of RuBP
Which of the following products of the light reactions of photosynthesis is consumed during the Calvin cycle?
NADPH
The overall function of the Calvin cycle is _____.
The overall function of the Calvin cycle is _____.
To explore the relationship between the two variables, it is useful to graph the data in a scatter plot, and then draw a regression line. But first, you must determine which variable should go on each axis of the graph.

What variable did the researchers intentionally vary in the experiment, and what are the units for this variable? (This is the independent variable.)

concentration of CO2 in the air, in parts per million
What variable's response to the independent variable was measured by the researchers, and what are the units for this variable?
average dry mass of one plant, in grams
Now that you have determined which variable goes on each axis, the graph can be constructed. An effective graph marks off the axes with just enough evenly spaced tick marks to accommodate the full set of data. Assuming that the x-axis tick marks will be separated by 200 (0, 200, 400, and so on), what is the largest value that should appear on the x-axis?
1200
Assuming that the y-axis tick marks will be separated by 10 (0, 10, 20, and so on), what is the largest value that should appear on the y-axis?
100
To compare the effect of rising atmospheric CO2 on C3 versus C4 plants, data from both types of plants can be placed on the same graph.

You should plot the data points for corn and velvetleaf using different symbols for each set of data, and add a key for the two symbols. Which of the following graphs correctly presents the data from the experiment?

Next you should draw a "best-fit" regression line for each set of points. A best-fit line does not pass through all or even most points. Instead, it is a straight line that passes as close as possible to all data points from that set. Which of the following graphs has the best-fit regression lines correctly drawn?
What is the relationship between increasing concentration of CO2 and the dry mass of corn?
As CO2 increases, the dry weight of corn decreases.

What is the relationship between increasing concentration of CO2 and the dry mass of velvetleaf?
As CO2 increases, the dry weight of velvetleaf increases.
Considering that velvetleaf is a weed invasive to cornfields, how would you predict increased CO2 concentration to affect interactions between the two species?
As atmospheric CO2 rises, velvetleaf weeds may grow larger and better compete with corn, reducing grain yields.
What is the estimated dry mass of corn and velvetleaf plants at an atmospheric CO2 concentration of 390 ppm (current levels)?
corn: 91 g; velvetleaf: 38 g
What is the estimated dry mass of corn and velvetleaf plants at an atmospheric CO2 concentration of 800 ppm?
corn: 84 g; velvetleaf: 50 g
If atmospheric CO2 concentration increases from 390 ppm to 800 ppm, what is the estimated percentage change in dry mass for corn? For velvetleaf?
The dry mass of corn would decrease by about 8%, and the dry mass of velvetleaf would increase by about 32%.
Do these results support the conclusion from other experiments that C3 plants have a better growth response than C4 plants under increased CO2 concentration? Why or why not?
Yes, because C3 velvetleaf had a positive growth response to increased CO2, but C4 corn had a negative growth response to it.

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
ATP and NADPH
Where does the Calvin cycle take place?
stroma of the chloroplast
What is the primary function of the Calvin cycle?
synthesize simple sugars from carbon dioxide
In the process of carbon fixation, RuBP attaches a CO2 to produce a six-carbon molecule, which is then split to produce two molecules of 3-phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs to happen to complete the Calvin cycle?
regeneration of RuBP
Refer to the figure. If the carbon atom of each of the incoming CO2 molecules is labeled with a radioactive isotope of carbon, which organic molecules will be radioactively labeled after one cycle?
B, C, D, and E
Refer to the figure. To identify the molecule that accepts CO2, Calvin and Benson manipulated the carbon-fixation cycle by either cutting off CO2 or cutting off light from cultures of photosynthetic algae.

They then measured the concentrations of various metabolites immediately following the manipulation. How would these experiments help identify the CO2 acceptor?

The CO2 acceptor concentration would increase when the CO2 is cut off, but decrease when the light is cut off.
Which of the following does NOT occur during the Calvin cycle?
release of oxygen
What compound provides the reducing power for Calvin cycle reactions?
NADPH
In C3 plants the conservation of water promotes _____.
photorespiration
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.

cytoplasm
C4 plants differ from C3 and CAM plants in that C4 plants _____.
transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
C4 plants occur more commonly in desert conditions because _____.
they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed
What would be the expected effect on plants if the atmospheric CO2 concentration was doubled?
C3 plants would have faster growth; C4 plants would be minimally affected.
Why are C4 plants able to photosynthesize with no apparent photorespiration?
They use PEP carboxylase to initially fix CO2.
CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they _____.

fix CO2 into organic acids during the night
The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?
Both minimize photorespiration but expend more ATP during carbon fixation.
If plant gene alterations cause plants to be deficient in photorespiration, what would most probably occur?
There would be more light-induced damage to the cells.
Compared to C3 plants, C4 plants _____.

can continue to fix CO2 even at lower CO2 concentrations and higher oxygen concentrations
Which of the following statements is true concerning the accompanying figure?
It represents a C4 photosynthetic system.
Referring to the accompanying figure, oxygen would inhibit the CO2 fixation reactions in _____.
cell II only
Photorespiration _____.
generates carbon dioxide and consumes ATP and oxygen
One of the important waste products of photosynthesis is oxygen gas. Where does this oxygen gas come from?
Oxygen is released when water is broken down to extract electrons and protons for use in the light reactions.
The light reactions produce _____.

oxygen, NADPH, and ATP
The thylakoid membranes bring together the components necessary to carry out the _____.
light reactions
Incoming photons of light energy initiate photosynthesis by _____.
exciting electrons in pigment molecules within the photosystems, raising them to a higher energy level
Which option properly summarizes the inputs and outputs of the Calvin cycle?
ATP + NADPH + 3CO 2 ? G3P
The use of non-C3 and non-CAM plants as crops may be limited in some regions because on hot, dry days, they close their stomata. What happens as a result of closing their stomata?
Oxygen from the light reactions in the leaf builds up. Water loss is reduced. In a process called photorespiration, rubisco binds oxygen instead of carbon dioxide.

Carbon dioxide is prevented from entering the leaf.

Which of the following equations represents photosynthesis?
6CO2 + 6H2O ? C6H12O6 + 6O2
In which of the following organelles does photosynthesis take place?
Chloroplast
What connects the two photosystems in the light reactions?
An electron transport chain
What two molecules are produced by the light reactions and used to power the Calvin cycle?
ATP and NADPH
What provides electrons for the light reactions?
H2O
What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
Carbon dioxide (CO2)
What transports electrons from the light reactions to the Calvin cycle?
NADPH
The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
thylakoids; stroma
The Calvin cycle occurs in the __________.
stroma
When chloroplast pigments absorb light, __________.

the pigments' electrons become excited
A photon of which of these colors would carry the most energy?
blue
The source of the oxygen produced by photosynthesis has been identified through experiments using radioactive tracers. The oxygen comes from __________.
water
Both mitochondria and chloroplasts __________.
use chemiosmosis to produce ATP
Why are C4 plants more suited to hot climates than C3 plants?
Unlike C3 plants, they keep fixing carbon dioxide even when the concentration of carbon dioxide in the leaf is low.
You could distinguish a thylakoid membrane from an inner mitochondrial membrane because the thylakoid membrane would __________.

have photosynthetic pigments
Building Vocabulary: Plant Adaptations to Hot, Dry Climates Can you match the following words to their descriptions? Part A Drag the terms at the left to the appropriate targets on the right to complete the sentences. Not all terms will be used.
C3 O2 photorespiration C4 CAM rubisco
In photosynthesis, plants use carbon from __________ to make sugar and other organic molecules.
carbon dioxide
What is the role of NADP+ in photosynthesis?
It is reduced and then carries electrons to the Calvin cycle.
The most important role of pigments in photosynthesis is to __________.

capture light energy
In photosynthesis, what is the fate of the oxygen atoms present in CO2? They end up __________.
in sugar molecules and in water
Molecular oxygen is produced during __________.
linear electron flow during the light reactions
During photosynthesis in a eukaryotic cell, an electrochemical gradient is formed across the __________.
thylakoid membrane
Which of the following groups of organisms contains only heterotrophs?
fungi
Which of the following occurs during the Calvin cycle?
ATP is hydrolyzed and NADPH is oxidized.

The reactions of the Calvin cycle are NOT directly dependent on light, but they usually do NOT occur at night. Why?
The Calvin cycle requires products only produced when the photosystems are illuminated.
Of the following, which occurs during the Calvin cycle?
CO2 is reduced.
Rubisco is __________.
the enzyme in plants that captures CO2 to begin the Calvin cycle
The energy used to produce ATP in the light reactions of photosynthesis comes from __________.
movement of H+ through a membrane
What structure is formed by the reaction center, light-harvesting complexes, and primary electron acceptors that cluster, and is located in the thylakoid membrane?
the photosystem
How does carbon dioxide enter the leaf?
through the stomata
What is the range of wavelengths of light that are absorbed by the pigments in the thylakoid membranes?
blue-violet and red-orange
In the Calvin cycle, CO2 is combined with __________.
a five-carbon compound to form an unstable six-carbon compound, which decomposes into two three-carbon compounds
Chlorophyll molecules are in which part of the chloroplast?
thylakoid membranes
Where do the electrons entering photosystem II come from?
water