Q: Which of the following is a correct equation for the overall process of oxygenic photosynthesis?

$$6\ \mathrm{CO_2$} + 6\ \mathrm{H_2O} + \text{light energy} \rightarrow \mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$}$$

Question 1

Which of the following best explains why oxygen is a byproduct of oxygenic photosynthesis, but not its primary goal?

Accepted Answer

Oxygen is produced as a result of splitting water to obtain electrons for the electron transport chain.

Question 2

In a stratified lake, which sequence correctly represents the order in which terminal electron acceptors are used as oxygen is depleted?

Accepted Answer

$$\mathrm{O_2$} \rightarrow \mathrm{NO_3$^-} \rightarrow \mathrm{$$MnO_2$$} \rightarrow \mathrm{Fe(OH)_3} \rightarrow \mathrm{SO_4$^{2-}} \rightarrow \mathrm{CO_2$}$$

Question 3

Which metabolic process is primarily responsible for the corrosion of pipelines in anaerobic environments?

Accepted Answer

Sulfate reduction by sulfate-reducing bacteria

Question 4

A bacterium living in the anoxic zone of a lake uses $$\mathrm{Fe(OH)_3} as a $$terminal electron acceptor. What is the likely electron donor and what is the product?

Accepted Answer

Electron donor: $$\mathrm{H_2$}$$; Product: $$\mathrm{Fe$$^{2+}$$}$$

Question 5

Which of the following best describes the role of carboxysomes in autotrophic bacteria?

Accepted Answer

They concentrate CO$$_2$$ and house Rubisco for efficient carbon fixation.

Question 6

Which of the following statements about bacteriochlorophyll and chlorophyll is correct?

Accepted Answer

Bacteriochlorophyll enables anoxygenic photosynthesis by absorbing longer wavelengths of light.

Question 7

Which of the following is a correct equation for the overall process of oxygenic photosynthesis?

Accepted Answer

$$6\ \mathrm{CO_2$} + 6\ \mathrm{H_2O} + 	ext{light energy} ightarrow \mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$}$$

Question 8

Which of the following best explains why different phototrophic bacteria occupy different depths in a Winogradsky column?

Accepted Answer

They have pigments tuned to absorb different wavelengths of light, allowing them to thrive at different depths.

Question 9

Which of the following is a unique feature of rhodopsin-based phototrophy compared to chlorophyll-based phototrophy?

Accepted Answer

It requires only two genes and directly pumps protons across the membrane upon light absorption.

Question 10

Which of the following best describes the function of Rubisco in the Calvin cycle?

Accepted Answer

It fixes CO$$_2$$ into an organic molecule, initiating the Calvin cycle.

Question 11

A microbe that uses $$\mathrm{H_2$} as an $$electron donor and $$\mathrm{SO_4$^{2-}} as an $$electron acceptor is classified as which of the following?

Accepted Answer

Sulfate reducer

Question 12

Which of the following is the correct sequence of events in the light-dependent reactions of oxygenic photosynthesis?

Accepted Answer

Excitation of chlorophyll, splitting of water, electron transport, generation of ATP and NADPH

Question 13

Which of the following best describes the ecological significance of syntrophic relationships in anaerobic environments?

Accepted Answer

They enable the complete degradation of organic compounds by coupling energetically unfavorable reactions with favorable ones.

Question 14

Which of the following is a correct description of the process of denitrification?

Accepted Answer

The reduction of nitrate ($$\mathrm{NO_3$^-}) to $$nitrogen gas ($$\mathrm{N_2$}) $$under anaerobic conditions.

Question 15

Which of the following is a product of the Calvin cycle that can be used for glycolysis or starch synthesis?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P)

Question 16

Which of the following best explains why methanogenesis is typically the last step in anaerobic respiration in a stratified environment?

Accepted Answer

Methanogenesis uses $$\mathrm{CO_2$} as an $$electron acceptor, which has the lowest reduction potential among common acceptors.

Question 17

Which of the following is a correct pairing of a lithotrophic process and its electron donor?

Accepted Answer

Iron oxidation: $$\mathrm{Fe$$^{2+}$$}$$

Question 18

Which of the following best describes the fate of the products of photosynthesis in a plant cell?

Accepted Answer

They can be stored as starch, used in respiration, or serve as precursors for biosynthesis.

Microbial Metabolic Diversity and Phototrophy: Mechanisms, Pathways, and Ecological Roles

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