Chapter 10 - Photosynthesis

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73 terms · BIO exam 3.

If photosynthesizing green algae are provided with CO₂ synthesized with heavy oxygen (¹⁸O), later analysis will show that all but one of the following compounds produced by the algae contain the ¹⁸O label. That one is..

O₂.

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

ATP and NADPH.

Photosynthesis is responsible for..

A) oxygen in the atmosphere.
B) the ozone layer.
C) most of the organic carbon on Earth's surface.
D) atmospheric CO₂.

Where does the Calvin cycle take place?

Stroma of the chloroplast.

In any ecosystem, terrestrial or aquatic, what group(s) is (are) always necessary?

Autotrophs.

In autotrophic bacteria, where are the enzymes located that can carry on carbon fixation (reduction of carbon dioxide to carbohydrate)?

In the cytosol.

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

Splitting water molecules.

A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?

Blue and violet.

Halobacterium has a photosynthetic membrane that is colored purple. Its photosynthetic action spectrum is exactly complementary (opposite to) the action spectrum for green plants. What wavelengths of light do the Halobacterium photosynthetic pigments absorb?

Blue and red.

In the thylakoid membranes, what is the main role of the antenna pigment molecules?

Harvest photons and transfer light energy to the reaction-center chlorophyll.

Which of the events listed below occurs in the light reactions of photosynthesis?

Light is absorbed and funneled to reaction-center chlorophyll a.

Which statement describes the functioning of photosystem II?

The electron vacancies in P680⁺ are filled by electrons derived from water.

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 photophosphorylation?

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 30,000 molecules of ATP consumed, but only 20,000 molecules of NADPH. 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 have the most direct effect on which of the following processes?

The synthesis of ATP.

What does the chemiosmotic process in chloroplasts involve?

Establishment of a proton gradient across the thylakoid membrane.

Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH 8 solution. What would be likely to happen?

The isolated chloroplasts will make ATP.

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

Thylakoid membrane and inner mitochondrial membrane.

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

The stroma to the thylakoid space.

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

Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.

Where are the molecules of the electron transport chain found in plant cells?

Thylakoid membranes of chloroplasts.

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

Both photosynthesis and respiration.

Reduction of oxygen to form water occurs during...

Respiration only.

Reduction of NADP⁺ occurs during...

Photosynthesis.

The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during..

Neither photosynthesis nor respiration.

Generation of proton gradients across membranes occurs during...

Both photosynthesis and respiration.

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

They are inversely related.

P680⁺ is said to be the strongest biological oxidizing agent. Why?

This molecule has a stronger attraction for electrons than oxygen, to obtain electrons from water.

Some photosynthetic bacteria (e.g., purple sulfur bacteria) have only photosystem I, whereas others (e.g., cyanobacteria) have both photosystem I and photosystem II. Which of the following might this observation imply?

Photosynthesis with only photosystem I is more ancestral.

Electron flow may be photoprotective (protective to light-induced damage). Which of the following experiments could provide information on this phenomenon?

Use mutated organisms that can grow but that cannot carry out cyclic flow of electrons and compare their abilities to photosynthesize in different light intensities against those of wild-type organisms.

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 thylakoids, protons travel through ATP synthase from the thylakoid space to the stroma. Therefore, the catalytic "knobs" of ATP synthase would be located...

On the stromal side of the membrane.

In metabolic processes of cell respiration and photosynthesis, prosthetic groups such as heme and iron-sulfur complexes are encountered in components of the electron transport chain. What do they do?

Oxidize and reduce during electron transport.

In a cyanobacterium, the reactions that produce NADPH occur in..

The light reactions alone.

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 that had both photosystem I and photosystem II.

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.

Where do the enzymatic reactions of 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 C₃ photosynthesis, the reactions that require ATP take place in..

The Calvin cycle alone.

In a plant leaf, the reactions that produce NADH occur in..

Neither the light reactions nor the Calvin cycle.

The NADPH required for the Calvin cycle comes from..

Reactions initiated in photosystem I.

Reactions that require CO₂ take place in..

The Calvin cycle alone.

Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?

The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, Pi, and NADP⁺ to the light reactions.

Three "turns" of the Calvin cycle generate a "surplus" molecule of glyceraldehyde 3-phosphate (G3P). Which of the following is a consequence of this?

The formation of sucrose and starch in plants involves assembling G3P molecules, with or without further rearrangements.

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.

The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?

The pH within the thylakoid is less than that of the stroma.

The phylogenetic distribution of the enzyme rubisco is limited to..

All known photoautotrophs, both bacterial and eukaryotic.

Photorespiration occurs when rubisco reacts RuBP with...

O₂.

In an experiment studying photosynthesis performed during the day, you provide a plant with radioactive carbon (¹⁴C) dioxide as a metabolic tracer. The ¹⁴C is incorporated first into oxaloacetate. The plant is best characterized as a..

C₄ plant.

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 daytime, thus reducing loss of water. They can do this because they..

Fix CO₂ into organic acids during the night.

Photorespiration lowers the efficiency of photosynthesis by ..

3-phosphoglycerate molecules.

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 the 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 relatively low CO2 concentrations and high oxygen concentrations.

If atmospheric CO₂ concentrations increase twofold or more, how will plants be affected, disregarding any changes in climate?

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

Plants photosynthesize only in the light. Plants respire...

Both in light and dark.

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. What color should she use to reduce overall light energy, but still maximize plant growth?

Blue.

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.

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.

An outcome of this experiment was to help determine..

The relationship between wavelengths of light and the rate of photosynthesis.

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 without passing light through a prism, what would you predict?

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

A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide.

Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed. What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?

Amixture of blue and red light.

A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide.

If the power fails and the lights go dark, what will happen to CO₂ levels?

CO₂ will rise as a result of both animal and plant respiration.

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.

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