Chapter 2 Multiple Choice Questions

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. What are photochemical reaction centres?

Small proteins that catalyse a chemical reaction correct incorrect

A protein that interacts with light correct incorrect

A large protein complex that converts light into chemistry useful for a cell correct incorrect

A large protein complex that uses chemical energy to emit light correct incorrect

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. What is charge separation?

It's a process whereby a chemical group is moved from the positively to the negatively charged side of the membrane correct incorrect

It's a process whereby positively and negatively charged chemical groups are rapidly distanced from each other in order to avoid their recombination and the loss of potentially useful energy correct incorrect

It's a process whereby an electron cycles through the photosynthetic membranes used to pump protons correct incorrect

It's another way to refer to electron transfer correct incorrect

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. How many types of photochemical reaction centres have evolved in nature?

1 correct incorrect

2 correct incorrect

3 correct incorrect

4 correct incorrect

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. When did oxygenic photosynthesis originate?

It's uncertain, at least it had originated by 2.3 Ga correct incorrect

Geochemical evidence suggests it had originated by 3.0 Ga correct incorrect

Difficult to tell, but oxygenic photosynthesis could be as old as life itself. correct incorrect

All of the above correct incorrect

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. What is the dominant evolutionary force that explains the distribution of photosynthesis across the tree of life?

Vertical inheritance followed by massive loss of photosynthesis across many lineages of prokaryotes correct incorrect

Horizontal gene transfer across close and distant lineages correct incorrect

It's hard to tell with certainty, but it's likely that both mechanisms of evolution played a part correct incorrect

None of the above correct incorrect

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. What's oldest, type I or type II photosystems?

Type I photosystems are older correct incorrect

Type II photosystems are older correct incorrect

The oldest photosystem likely combined traits from both, so it would have been a 1.5 photosystem. correct incorrect

It's difficult to say, but the earliest stage in the evolution of the photosystems that can be inferred from current data is the structural and functional specialization that led to both photosystems correct incorrect

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. Was the ancestral photosystem II capable of water oxidation?

Yes. Structural and functional evidence suggests that the ancestral photosystem II was a homodimer with the capacity to split water on either side of the reaction centre correct incorrect

No. The ancestral photosystem II was like the proteobacterial anoxygenic type II photosystem correct incorrect

No. the ancestral photosystem II was like the type I photosystem of heliobacteria correct incorrect

None of the above correct incorrect

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. Where do chlorophyll and bacteriochlorophylls come from?

They originated from hemes correct incorrect

They originated from nitrogenases correct incorrect

It's unclear but we know for sure that bacteriochlorophylls gave rise to chlorophylls correct incorrect

The evolution of tetrapyrroles is complex and overall, poorly understood correct incorrect

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. How did cyanobacteria evolve the capacity to oxidize water?

Cyanobacteria evolved in environments particularly rich in sources of manganese correct incorrect

It's difficult to tell how exactly water oxidation evolved, but there's evidence that the process originated long before cyanobacteria emerged as the group that we understand today correct incorrect

It's difficult to tell but there's evidence that cyanobacteria obtained genes for photosynthesis from Proteobacteria and Heliobacteria, and at some point after that, water oxidation became possible correct incorrect

All of the above correct incorrect

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. When did photosystems stop evolving?

When they reached optimal functionality correct incorrect

Around the time of the GOE1 correct incorrect

During the early Archean correct incorrect

The photosystems continue to evolve, and many novel adaptations have occurred through the evolutionary history of life correct incorrect