Chapter 3 Multiple Choice Questions

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. What are thylakoids?

The membrane system of the mitochondria correct incorrect

The membrane system used by bacteria for respiration correct incorrect

The photosynthetic membrane system of cyanobacteria and photosynthetic eukaryotes correct incorrect

The fruits of the thylakon tree correct incorrect

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. One of the following isn't found embedded in the thylakoid membrane, which one?

Photosystem I correct incorrect

Cytochrome b₆f correct incorrect

ATP synthase correct incorrect

Rubisco correct incorrect

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. What are phycobilisomes?

Phycobilisomes are the light harvesting complexes of cyanobacteria correct incorrect

Phycobilisomes are the light harvesting complexes of red algae correct incorrect

Phycobilisomes are the light harvesting complexes of the gloucophytes correct incorrect

All of the above correct incorrect

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. During photosystem II's water oxidation cycle, the four Mn atoms of the oxygen-evolving cluster cycle through a number of oxidation steps. What is the oxidation state of the four Mn atoms in the most oxidized S₃ state?

+2, +2, +2, +2 correct incorrect

+2, +2, +3, +3 correct incorrect

+4, +4, +4, +4 correct incorrect

+4, +4, +5, +5 correct incorrect

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. What is the function of the cytochrome b₆f complex?

The complex shuttles electrons from PSII to PSI, and this electron transfer process is coupled to the movement of protons across the membrane correct incorrect

The complex uses light to energize the movement of protons across the membrane correct incorrect

The complex takes electrons from plastoquinone and use them to reduce NADP⁺ correct incorrect

The complex shuttles electrons from PSI to PSII, which are then used to reduce plastoquinone correct incorrect

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. In contrast to photosystem II, photosystem I retains a degree of homodimeric function. What does this mean?

It means that the two core subunits of photosystem I, PsaA and PsaB, are identical correct incorrect

It means that charge separation can occur on both branches of the reaction centre core at the same time correct incorrect

It means that photosystem I can split water on both sides of the reaction centre correct incorrect

None of the above correct incorrect

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. What happens when rubisco reacts with O₂ instead of CO₂?

This is known as photooxygenation. The reaction generates ROS, which is toxic to the organisms and needs to be scavenged correct incorrect

The cell gains energy because the oxygenated sugars have higher reductive power correct incorrect

Rubisco becomes inactivated. It means that it needs to be degraded and resynthesized at very high turnover rates correct incorrect

This is known as photorespiration. The process leads to the formation of 2-phosphoglycolate, which is a waste product and needs to be recycled to 3-phosphoglycerate with at an energetic cost correct incorrect

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. What is the difference between C3 and C4 photosynthesis?

In C3 photosynthesis the initial product of carbon fixation is a 3-carbon compound, 3-phosphoglycerate; while in C4 photosynthesis, it is the 4-carbon compound, oxaloacetate correct incorrect

In C3 photosynthesis, three CO₂ molecules are fixed per 8 absorbed photons; while in C4 photosynthesis, four CO₂ molecules are fixed instead correct incorrect

In C3 photosynthesis, three molecules of CO₂ are fixed during the day, while in C4 photosynthesis four CO₂ are fixed during the night correct incorrect

None of the above correct incorrect

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. What is the CAM carbon assimilation pathway?

In the CAM pathway glutamine is carboxylated first, producing glutamate correct incorrect

The CAM pathway resembles C4 photosynthesis, however oxaloacetate is produced at night, while decarboxylation and CO₂ assimilation via rubisco occurs during the day correct incorrect

It is the only CO₂ fixation pathway in red algae correct incorrect

The CAM pathway resembles C3 photosynthesis, however oxaloacetate is produced in mesophyll cells, while decarboxylation and CO₂ assimilation via rubisco occurs in the bundle-sheath cells correct incorrect

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. How does nitrogen enter the biosphere?

N₂ gas is first converted to glutamate by glutamine synthase correct incorrect

All photosynthetic organisms can use nitrogenase to fix N₂ directly from air correct incorrect

Most of the nitrogen available to life is produced abiotically through lightning and the weathering of rocks correct incorrect

Cyanobacteria and other prokaryotes fix N₂ using nitrogenase. Algae and plants depend on microbially fixed nitrogenous compounds found in the environment correct incorrect