BIO Ch 10

Which processes establish a gradient of protons to drive ATP synthesis? -Mitochondrial electron transport chain and photosystem I reactions -Glycolysis and photosystem I reactions -Photosystem II and mitochondrial electron transport chain reactions -Photosystem II and Calvin cycle reactions

Photosystem II and mitochondrial electron transport chain 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.

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.

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 The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.

When an electron has high potential energy it can do what two things?

fall back to its ground state and release heat, or produce light as fluorescence.

pheophytin is identical to chlorphyll except that pheophytin lacks a ________ atom in its head region

magnesium

anoxygenic

no oxygen producing photosynthesis

What molecule is released when water is split in the light reactions of photosynthesis?

oxygen

oxygenic

oxygen producing photosynthesis

In photosystem II the action begins when the antenna complex transmits resonance energy to the reaction center, where the electron acceptor ________ comes into play.

pheophytin

In C3 plants the conservation of water promotes _____.

photorespiration

When photons are absorbed by pigments in chloroplasts though, only about 2 % of the excited electrons produce fluorescence. The other 98% of the energized pigments use their excited electrons to drive _________

photosynthesis

Which process produces oxygen?

photosynthesis

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

photosystem 1 = C

Chlorophyll can be found in _____.

photosystem 1 and 2 = A and C

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

photosystem 2 = A

The enhancement effect occurs because photosynthesis is much more efficient with both ________ operate together.

photosystems

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

When excited electrons leave phtosystem II and enter the ETC, the photosystem becomes so electronegative that enzymes can remove electrons from water, leaving ______ and _______.

protons and oxygen

_____ has a longer wavelength than _____. Green ... yellow Red ... green Violet ... blue Blue ... green Yellow ... red

red... green

During the Calvin cycle, carbon dioxide is _____ to drive the formation of sugars.

reduced

The enzyme that catalyzes the fixation of carbon dioxide in photosynthesis is _____.

rubisco

quinone

small hydrophobic molecule that can transport electrons between molecules

The light energy harvested by photosystem II is responsible for?

splitting water

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

splitting water molecules

______ are normally open during the day, when photosynthesis is occurring, and closed at night.

stomata

What is the primary function of the Calvin cycle?

synthesize simple sugars from CO2

Reactions that require CO2 take place in _____.

the calvin cycle alone

Which set of reactions uses H2O and produces O2?

the light dependent reactions

Where does the calvin cycle occur?

the stroma

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

the stroma to the thylakoid space

Electrons that reduce pheophytin are passed through additional carriers to an elecron transport chain in the __________ membrane

thylakoid

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

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

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

true

Because photorespiration cosumes energy and releases fixed CO2, it _______ photosynthesis

undoes

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

The light reactions of photosynthesis use _____ and produce _____.

water and NADPH

In the Z-scheme ____ is the initial electron donor and ____ is the final electron acceptor.

water; NADP+ Water becomes oxidized, releasing oxygen gas, and NADP+ becomes reduced, producing NADPH.

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 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.

In the _______ of light, the electron acceptor does not accept electrons

absence

In the thylakoid membrane, 200-300 chlorphyll molecules and accessory pigments are organized by an array of proteins to form structures called the ________ ________ and the ________ center

antenna complex, reaction

The proteins of the electron transport chain active in the light-dependent reactions _____.

are membrane proteins present in the thylakoid

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

both photosynthesis and respiration

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.

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.

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

3

What would the results of this experiment look like if the pigments that drive photosynthesis in the algae were to absorb most strongly at 500 nm and 560 nm?

500 nm and 560 nm are in the green region of the electromagnetic spectrum, which is where the rate of photosynthesis would be highest.

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

6

Which of these equations best summarizes photosynthesis?

6 CO2 + 6 H2O → C6H12O6 + 6 O2

Which is the best estimate for the number of photons required to produce one glucose molecule from CO2 (ignoring the possible effects of cyclic electron flow and photorespiration)?

96 Fixation of six CO2 to produce one glucose molecule (Calvin cycle) requires 18 ATP and 12 NADPH. Light-capturing reactions require four photons to produce two NADPH plus approximately four photons to produce one ATP. So, production of necessary ATP requires approximately 72 (18 × 4) photons and production of necessary NADPH requires an additional 24 (12 × 4/2) photons.

identify a chloroplast

A

Which of these phosphorylates ADP to make ATP

ATP synthase = E

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

In combination, photosystems II and I Produce chemical energy stored in ____ and _______

ATP, NADPH

Which of the following BEST characterizes gas exchange in animal versus plant metabolism: -Animals take in and release both O2 and CO2. Plants take in CO2 and release O2. -Animals take in O2 and release CO2. Plants take in and release both O2 and CO2. -Both animals and plants take in and release O2 and CO2. -Animals take in O2 and release CO2. Plants take in CO2 and release O2.

Animals take in O2 and release CO2. Plants take in and release both O2 and CO2.

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle? A) CO2 and glucose B) ATP and NADPH C) electrons and H+ D) ADP, i, and NADP+ E) H2O and O2

B) ATP and NADPH

Which of the following statements best describes the relationship between photosynthesis and respiration? A) Photosynthesis is catabolic; respiration is anabolic. B) Photosynthesis stores energy in complex organic molecules; respiration releases energy from complex organic molecules C) Respiration runs the biochemical pathways of photosynthesis in reverse. D) Photosynthesis occurs only in plants; respiration occurs only in animals. E) ATP molecules are produced in photosynthesis but not in aerobic respiration.

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

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, E

Pheophytin accepts high-energy electrons from the excited reaction center ________

Chlorophylls

identify a thylakoid

D

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)? A) ATP is synthesized from the energy absorbed. B) A carboxylation reaction of the Calvin cycle occurs. C) Electrons are stripped from NADPH. D) An electron is excited.

D) An electron is excited.

Which of the following sequences correctly represents the flow of electrons during photosynthesis? A) NADPH → electron transport chain → O2 B) NADPH → O2 → C O2 C) NADPH → chlorophyll → Calvin cycle D) H2O → NADPH → Calvin cycle E) H2O → photosystem I → photosystem II

D) H2O → NADPH → Calvin cycle

identify the stroma

E

Which statement is correct regarding how CO2 is delivered to rubisco in C3, C4, or CAM plants?

In C4 plants, CO2 is delivered via 4-carbon organic acids.

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).

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.

In light reactions, light energy is used to oxidixe H2O to O2. The electrons derived form this oxidation reaction in the light reactions are used to reduce NADP to NADPH. The Calvin Cycle oxidizes the light-reactions product NADPH to NADP. The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce CO2 to G3P.

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.

In Engelmann's experiment, he used aerotactic (oxygen-seeking) bacteria to determine which wavelengths of visible light were most effective in driving the reactions of photosynthesis in green algae. A diagram of his apparatus is shown below. Can you deduce the logical link between light of different wavelengths and the distribution of bacteria that Engelmann observed?

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 is the role of plastocyanin in the Z-scheme model?

It shuttles electrons between the cytochrome complex and photosystem I.

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

NADPH

Electrons from photosystem I are used to produce _______, which is a reducing agent similar in function to the NADH and FADH2 produced by the citric acid cycle.

NADPH

The light-independent reactions of plants function to make organic molecules using carbon dioxide as a carbon source. What is the electron source that helps reduce carbon dioxide to sugars and other organic molecules?

NADPH

Which of the following molecules is the primary product of photosystem I? Oxygen NADPH ATP Carbon dioxide

NADPH

What two molecules produced during the light-capturing reactions of photosynthesis are used in the Calvin cycle?

NADPH & ATP These two molecules are produced in the light-capturing reactions of photosynthesis and are used to provide energy and reducing power to convert carbon dioxide into sugar.

Consistently overwatering a potted tomato plant will eventually kill it. Using the map, suggest why waterlogged soil results in plant death. -CO2 cannot reach the chloroplasts, preventing production of glucose by the Calvin cycle. The plant cannot make food and starves. -O2 cannot reach respiring root cells. The plant cannot oxidize food and starves. -Light energy cannot reach the chloroplasts, preventing ATP and NADPH production by the light-dependent reactions. The plant cannot make food and starves. -CO2 cannot reach photosynthesizing root cells, preventing production of glucose by the Calvin cycle. The plant cannot make food and starves.

O2 cannot reach respiring root cells. The plant cannot oxidize food and starves.

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

Photophosphorylation The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production.

An investigator exposes chloroplasts to 700-nm photons and observes low O2 production, but high ATP production. Which of the following best explains this observation? A. Electron transport has stopped and ATP is being produced by the Calvin cycle. B. Photosystem II is not splitting water, and the ATP is being produced by cycling electrons via photosystem I. C. The O2 is being converted to water as a terminal electron acceptor in the production of ATP. D. The electrons from water are directly transferred to NADP+, which is used to generate ATP.

Photosystem II is not splitting water, and the is being produced by cycling electrons via photosystem I.

The molecules that absorb only certain wavelengths of light energy from the sun to begin the photosynthetic reactions are called _____.

Pigments absorb certain wavelengths of light and can transfer this captured energy to begin photosynthesis.

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

Regeneration of RuBP

When a red or blue photon strikes a pigment molecule in the antenna complex, the energy is absorbed and an electron is excited in response. This energy - but not the electron itself - is passed to a nearby chlorophyll molecule where another electron is excited in response.

Resonance energy transfer

Carbon fixation involves the addition of carbon dioxide to _____.

RuBP

In the Calvin cycle, why are fewer than six RuBP molecules required to fix six molecules of CO2?

RuBP is regenerated during the Calvin Cycle In the regeneration phase of the Calvin cycle, the carbon skeletons of five G3P molecules are rearranged into three RuBP molecules, so fewer than six RuBP molecules are required to fix six CO2.

Plant leaves contain openings called _____, which allow the diffusion of carbon dioxide into the leaf tissue.

Stomata (singular: stoma) consist of two guard cells and the pore between them.

During photosynthesis, the light energy from the sun is captured and stored in the bonds of _____.

Sugars - glucose

Which statement accurately describes the roles of the light-dependent reactions (LDRs), the Calvin cycle, and cellular respiration? -The LDRs convert small high-energy molecules into sugars, the Calvin cycle breaks down sugars to produce ATP, and cellular respiration converts light energy into chemical energy. -The LDRs convert light energy into chemical energy, the Calvin cycle breaks down sugars to produce ATP, and cellular respiration converts small high-energy molecules into sugars. -The LDRs convert small high-energy molecules into sugars, the Calvin cycle converts light energy into chemical energy, and cellular respiration breaks down sugars to produce ATP. -The LDRs convert light energy into chemical energy, the Calvin cycle converts small high-energy molecules into sugars, and cellular respiration breaks down sugars to produce ATP.

The LDRs convert light energy into chemical energy, the Calvin cycle converts small high-energy molecules into sugars, and cellular respiration breaks down sugars to produce ATP.

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. If you ran the same experiment as Engelmann without passing light through a prism, what would you predict?

The bacteria would be relatively evenly distributed along the algal filaments.

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.

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.

Why are violet-to-blue and red photons the most effective at driving photosynthesis?

These are the wavelengths of light absorbed by chlorophyll molecules.

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

They convert carbon dioxide to sugar

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.

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.

Cellular respiration generates _________, which in turn is used as a carbon source for the synthesis of sugars during photosynthesis. Cellular respiration also generates ____ and _______, which are used in various chemical reactions in the plant cell.

carbon dioxide, ATP, water

When a chlorophyll molecule is excited in the reaction center, its excited electron is transferred to an electron acceptor, which becomes reduced and the electromagnetic energy is transformed into?

chemical energy

Photosystem II triggers _________ and _________ in the chloroplast

chemiosmosis, ATP synthase

Carotenoids absorb wavelengths of light that are not absorbed by ________. As a result, they extend the range of wavelengths that can drive __________.

chlorophyll, photosynthesis

A mutually dependent relationship exists between _________ and _________ in the plant cell.

chloroplasts and mitochondria

Photosynthesis, which occurs in ________, generates the sugars and oxygen gas that are used in mitochondria for?

chloroplasts, cellular respiration

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

cytoplasm

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

electron transport chain = B

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

false The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.

Carotenoids "quench" ______ ________ by accepting or stabilizing unpaired electrons. As a result they protect chlorophyll molecules from harm.

free radicals

Which statement is most accurate concerning how photosystem II compares to the electron transport chain (ETC) of mitochondria?

in both systems, ATP is produced by chemiosmosis

Chlorophyll molecules donate electrons to an electron acceptor ____.

in the reaction center chlorophylls are the only chlorophylls that donate electrons to an electron acceptor.

plastocyanin is critical because?

it forms a physical link between photosystem I and II