Mastering Biology: Chapter 10 - Flashcards

question

The light reactions of photosynthesis supply the Calvin cycle with

answer

ATP and NADPH.

question

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

answer

H2O ? NADPH ? Calvin cycle

question

How is photosynthesis similar in C4 plants and CAM plants?

answer

In both cases, rubisco is not used to fix carbon initially.

question

Which of the following statements is a correct distinction between autotrophs and heterotrophs?

answer

Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.

question

Which of the following does not occur during the Calvin cycle?

answer

release of oxygen

question

In mechanism, photophosphorylation is most similar to

answer

oxidative phosphorylation in cellular respiration.

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Which process is most directly driven by light energy?

answer

removal of electrons from chlorophyll molecules

question

Select the most accurate statement describing the basic function of the light reactions of photosynthesis.

answer

The basic function of the light reactions of photosynthesis is the conversion of solar energy to chemical energy.

question

Select the correct molecule that is the main product of the Calvin cycle.

answer

G3P

question

What is the basic role of CO2 in photosynthesis?

answer

CO2 is fixed or incorporated into organic molecules.

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Select the correct statement about the Calvin cycle.

answer

The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.

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Why are plants classified as producers?

answer

Plants are classified as producers because they fix inorganic carbon into organic molecules.

question

Which of the following is generally true about the stratosphere?

answer

It is very dry.

question

Based on current findings, which of the following is true?

answer

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.

question

Where was the thinning of ozone initially discovered?

answer

Over the Antarctic

question

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?

answer

Montreal Protocol

question

Which of the following two things worked in conjunction to make CFCs harmful to the ozone?

answer

chlorine and sunlight

question

Identify the chloroplast.

answer

A

question

Identify the stroma.

answer

E

question

Identify a thylakoid.

answer

D

question

Which of these equations best summarizes photosynthesis?

answer

6 CO2 + 6 H2O ? C6H12O6 + 6 O2

question

Where does the Calvin cycle occur?

answer

E

question

The light reactions of photosynthesis use _____ and produce _____.

answer

water ... NADPH

question

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.

answer

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

question

Plants are photoautotrophs. What does this mean?

answer

They use light energy to drive the synthesis of organic molecules from inorganic materials.

question

The ultimate source of energy to support most life on Earth is _____.

answer

sunlight

question

The photosynthetic membranes are found in the _____ in plant cells.

answer

chloroplasts

question

The process of photosynthesis probably originated _____.

answer

in prokaryotes

question

In autotrophic bacteria, where is chlorophyll located?

answer

in the infolded plasma membrane

question

Plants photosynthesize _____.

answer

only in the light but respire in light and dark

question

Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide. In fact, it comes from _____.

answer

water

question

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 _____.

answer

O2

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Every ecosystem must have _____.

answer

autotrophs

question

When oxygen is released as a result of photosynthesis, it is a direct by-product of _____.

answer

splitting water molecules

question

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.

answer

Cup 4 had the slowest rate of photosynthesis because it had the least baking soda.

question

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.

answer

*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).

question

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.

answer

no energy energy no energy energy no energy

question

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.

answer

*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

question

_____ has a longer wavelength than _____.

answer

Red ... green

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Which of these phosphorylates ADP to make ATP?

answer

C

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_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.

answer

B

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_____ splits water into 1/2 O2, H+, and e- .

answer

A

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Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.

answer

C

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Chlorophyll can be found in _____.

answer

A and C

question

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.

answer

*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.

question

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.

answer

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.

question

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

answer

*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.

question

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

answer

Photophosphorylation

question

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.

answer

False

question

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?

answer

Proton gradient

question

Which of the following particles can pass through the ATP synthase channel?

answer

Protons

question

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

answer

False

question

In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____.

answer

ultraviolet radiation and infrared radiation

question

Which of the following is a product of the light reactions of photosynthesis?

answer

oxygen, ATP, and NADPH

question

When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____.

answer

splitting water

question

Photosynthesis is a redox reaction. This means that H2O is _____ during the light reactions and CO2 is _____ during the Calvin cycle.

answer

oxidized...reduced

question

Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions?

answer

435 nm

question

Which wavelength of light is best absorbed by chlorophyll b?

answer

455 nm

question

You obtain the pigments called carotenoids in your diet when you eat carrots. Why do carotenoids appear yellow and orange?

answer

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

question

Can you tell from these absorption spectra whether red light is effective in driving photosynthesis?

answer

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.

question

If only chlorophyll a were involved in the light reactions, would blue light (wavelength about 490 nm) be effective in driving photosynthesis?

answer

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

question

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?

answer

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.

question

Which wavelengths of light drive the highest rates of photosynthesis? Select the two best answers.

answer

400-450 nm 670-680 nm

question

The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different?

answer

Other pigments absorb light in addition to chlorophyll a.

question

What wavelength of light in the figure is most effective in driving photosynthesis?

answer

420 mm

question

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?

answer

Bacteria congregated in these areas because these areas had the most oxygen being released.

question

An outcome of Engelmann's experiment was to help determine the relationship between _____.

answer

wavelengths of light and the rate of photosynthesis

question

What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?

answer

a mixture of blue and red light

question

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?

answer

blue and violet

question

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?

answer

green and yellow

question

Why are there several structurally different pigments in the reaction centers of photosystems?

answer

This arrangement enables the plant to absorb light energy of a variety of wavelengths.

question

If pigments from a particular species of plant are extracted and subjected to paper chromatography, which of the following is most likely?

answer

Paper chromatography would separate the pigments from a particular plant into several bands.

question

In autumn, the leaves of deciduous trees change colors. This is because chlorophyll is degraded and _____.

answer

carotenoids and other pigments are still present in the leaves

question

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?

answer

An electron is excited.

question

As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?

answer

It is used to establish and maintain a proton gradient.

question

The final electron acceptor associated with photosystem I is _____.

answer

NADP

question

The electrons of photosystem II are excited and transferred to electron carriers. From which molecule or structure do the photosystem II replacement electrons come?

answer

water

question

In the thylakoid membranes, the pigment molecules in a light-harvesting complex _____.

answer

absorb and transfer light energy to the reaction-center chlorophyll

question

Which of the following are directly associated with photosystem I?

answer

receiving electrons from the thylakoid membrane electron transport chain

question

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 _____.

answer

test for liberation of O2 in the light

question

What are the products of linear electron flow?

answer

ATP and NADPH

question

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?

answer

cyclic electron flow

question

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 _____.

answer

synthesis of ATP

question

In a plant cell, where are the ATP synthase complexes located?

answer

thylakoid membrane and inner mitochondrial membrane

question

In mitochondria, chemiosmosis moves protons from the intermembrane space into the matrix, whereas in chloroplasts, chemiosmosis moves protons from the _____.

answer

thylakoid space to the stroma

question

Which of the following statements best describes the relationship between photosynthesis and respiration?

answer

Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules

question

In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during _____.

answer

photosynthesis and respiration

question

Carbon dioxide is split to form oxygen gas and carbon compounds _____.

answer

in neither photosynthesis nor respiration

question

What is the relationship between the wavelength of light and the quantity of energy per photon?

answer

They are inversely related.

question

P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?

answer

It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.

question

Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?

answer

They protect against oxidative damage from excessive light energy.

question

In a plant, the reactions that produce molecular oxygen (O2) take place in _____.

answer

the light reactions alone

question

The accumulation of free oxygen in Earth's atmosphere began with the origin of _____.

answer

cyanobacteria using photosystem II

question

In its mechanism, photophosphorylation is most similar to _____.

answer

oxidative phosphorylation in cellular respiration

question

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?

answer

blue

question

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 _____.

answer

be higher in the light, but lower in the dark

question

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.

answer

*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.

question

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.

answer

*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.

question

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.

answer

*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.

question

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.

answer

*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.

question

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.

answer

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.

question

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.

answer

*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.

question

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.)

answer

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

question

Carbon fixation involves the addition of carbon dioxide to _____.

answer

RuBP

question

After 3-PGA is phosphorylated, it is reduced by _____.

answer

NADPH

question

How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?

answer

6

question

In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?

answer

3

question

Which process produces oxygen?

answer

Photosynthesis

question

Which set of reactions uses H2O and produces O2?

answer

The light-dependent reactions

question

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?

answer

The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars.

question

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

answer

True

question

Which of the following molecules is the primary product of photosystem I?

answer

NADPH

question

What is the biological significance of the light-independent reactions of photosynthesis?

answer

They convert carbon dioxide to sugar.

question

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

answer

The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.

question

Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?

answer

Regneration of RuBP

question

Which of the following products of the light reactions of photosynthesis is consumed during the Calvin cycle?

answer

NADPH

question

The overall function of the Calvin cycle is _____.

answer

The overall function of the Calvin cycle is _____.

question

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.)

answer

concentration of CO2 in the air, in parts per million

question

What variable's response to the independent variable was measured by the researchers, and what are the units for this variable?

answer

average dry mass of one plant, in grams

question

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?

answer

1200

question

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?

answer

100

question

What is the relationship between increasing concentration of CO2 and the dry mass of corn?

answer

As CO2 increases, the dry weight of corn decreases.

question

What is the relationship between increasing concentration of CO2 and the dry mass of velvetleaf?

answer

As CO2 increases, the dry weight of velvetleaf increases.

question

Considering that velvetleaf is a weed invasive to cornfields, how would you predict increased CO2 concentration to affect interactions between the two species?

answer

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

question

What is the estimated dry mass of corn and velvetleaf plants at an atmospheric CO2 concentration of 390 ppm (current levels)?

answer

corn: 91 g; velvetleaf: 38 g

question

What is the estimated dry mass of corn and velvetleaf plants at an atmospheric CO2 concentration of 800 ppm?

answer

corn: 84 g; velvetleaf: 50 g

question

If atmospheric CO2 concentration increases from 390 ppm to 800 ppm, what is the estimated percentage change in dry mass for corn? For velvetleaf?

answer

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

question

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?

answer

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

question

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

answer

ATP and NADPH

question

Where does the Calvin cycle take place?

answer

stroma of the chloroplast

question

What is the primary function of the Calvin cycle?

answer

synthesize simple sugars from carbon dioxide

question

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?

answer

regeneration of RuBP

question

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?

answer

B, C, D, and E

question

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?

answer

The CO2 acceptor concentration would increase when the CO2 is cut off, but decrease when the light is cut off.

question

Which of the following does NOT occur during the Calvin cycle?

answer

release of oxygen

question

What compound provides the reducing power for Calvin cycle reactions?

answer

NADPH

question

In C3 plants the conservation of water promotes _____.

answer

photorespiration

question

In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.

answer

cytoplasm

question

C4 plants differ from C3 and CAM plants in that C4 plants _____.

answer

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

question

C4 plants occur more commonly in desert conditions because _____.

answer

they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed

question

What would be the expected effect on plants if the atmospheric CO2 concentration was doubled?

answer

C3 plants would have faster growth; C4 plants would be minimally affected.

question

Why are C4 plants able to photosynthesize with no apparent photorespiration?

answer

They use PEP carboxylase to initially fix CO2.

question

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they _____.

answer

fix CO2 into organic acids during the night

question

The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?

answer

Both minimize photorespiration but expend more ATP during carbon fixation.

question

If plant gene alterations cause plants to be deficient in photorespiration, what would most probably occur?

answer

There would be more light-induced damage to the cells.

question

Compared to C3 plants, C4 plants _____.

answer

can continue to fix CO2 even at lower CO2 concentrations and higher oxygen concentrations

question

Which of the following statements is true concerning the accompanying figure?

answer

It represents a C4 photosynthetic system.

question

Referring to the accompanying figure, oxygen would inhibit the CO2 fixation reactions in _____.

answer

cell II only

question

Photorespiration _____.

answer

generates carbon dioxide and consumes ATP and oxygen

question

One of the important waste products of photosynthesis is oxygen gas. Where does this oxygen gas come from?

answer

Oxygen is released when water is broken down to extract electrons and protons for use in the light reactions.

question

The light reactions produce _____.

answer

oxygen, NADPH, and ATP

question

The thylakoid membranes bring together the components necessary to carry out the _____.

answer

light reactions

question

Incoming photons of light energy initiate photosynthesis by _____.

answer

exciting electrons in pigment molecules within the photosystems, raising them to a higher energy level

question

Which option properly summarizes the inputs and outputs of the Calvin cycle?

answer

ATP + NADPH + 3CO 2 ? G3P

question

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?

answer

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.

question

Which of the following equations represents photosynthesis?

answer

6CO2 + 6H2O ? C6H12O6 + 6O2

question

In which of the following organelles does photosynthesis take place?

answer

Chloroplast

question

What connects the two photosystems in the light reactions?

answer

An electron transport chain

question

What two molecules are produced by the light reactions and used to power the Calvin cycle?

answer

ATP and NADPH

question

What provides electrons for the light reactions?

answer

H2O

question

What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?

answer

Carbon dioxide (CO2)

question

What transports electrons from the light reactions to the Calvin cycle?

answer

NADPH

question

The light reactions take place in the _________ and the Calvin cycle takes place in the _________.

answer

thylakoids; stroma

question

The Calvin cycle occurs in the __________.

answer

stroma

question

When chloroplast pigments absorb light, __________.

answer

the pigments' electrons become excited

question

A photon of which of these colors would carry the most energy?

answer

blue

question

The source of the oxygen produced by photosynthesis has been identified through experiments using radioactive tracers. The oxygen comes from __________.

answer

water

question

Both mitochondria and chloroplasts __________.

answer

use chemiosmosis to produce ATP

question

Why are C4 plants more suited to hot climates than C3 plants?

answer

Unlike C3 plants, they keep fixing carbon dioxide even when the concentration of carbon dioxide in the leaf is low.

question

You could distinguish a thylakoid membrane from an inner mitochondrial membrane because the thylakoid membrane would __________.

answer

have photosynthetic pigments

question

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.

answer

C3 O2 photorespiration C4 CAM rubisco

question

In photosynthesis, plants use carbon from __________ to make sugar and other organic molecules.

answer

carbon dioxide

question

What is the role of NADP+ in photosynthesis?

answer

It is reduced and then carries electrons to the Calvin cycle.

question

The most important role of pigments in photosynthesis is to __________.

answer

capture light energy

question

In photosynthesis, what is the fate of the oxygen atoms present in CO2? They end up __________.

answer

in sugar molecules and in water

question

Molecular oxygen is produced during __________.

answer

linear electron flow during the light reactions

question

During photosynthesis in a eukaryotic cell, an electrochemical gradient is formed across the __________.

answer

thylakoid membrane

question

Which of the following groups of organisms contains only heterotrophs?

answer

fungi

question

Which of the following occurs during the Calvin cycle?

answer

ATP is hydrolyzed and NADPH is oxidized.

question

The reactions of the Calvin cycle are NOT directly dependent on light, but they usually do NOT occur at night. Why?

answer

The Calvin cycle requires products only produced when the photosystems are illuminated.

question

Of the following, which occurs during the Calvin cycle?

answer

CO2 is reduced.

question

Rubisco is __________.

answer

the enzyme in plants that captures CO2 to begin the Calvin cycle

question

The energy used to produce ATP in the light reactions of photosynthesis comes from __________.

answer

movement of H+ through a membrane

question

What structure is formed by the reaction center, light-harvesting complexes, and primary electron acceptors that cluster, and is located in the thylakoid membrane?

answer

the photosystem

question

How does carbon dioxide enter the leaf?

answer

through the stomata

question

What is the range of wavelengths of light that are absorbed by the pigments in the thylakoid membranes?

answer

blue-violet and red-orange

question

In the Calvin cycle, CO2 is combined with __________.

answer

a five-carbon compound to form an unstable six-carbon compound, which decomposes into two three-carbon compounds

question

Chlorophyll molecules are in which part of the chloroplast?

answer

thylakoid membranes

question

Where do the electrons entering photosystem II come from?

answer

water

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