Photosynthesis

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Biology › Photosynthesis

Questions 1 - 10
1

Which of the following is an example of an anabolic pathway?

Photosynthesis

Glycolysis

Citric acid cycle

Fatty acid decarboxylation

All of these

Explanation

An anabolic pathway is a pathway in which smaller molecules are combined to form larger ones. This type of pathway usually requires energy to complete the combinations required. Photosynthesis is an example of this, because it combines carbon dioxide molecules to form glucose. The rest of the listed processes are catabolic pathways.

2

Which of the following is an example of an anabolic pathway?

Photosynthesis

Glycolysis

Citric acid cycle

Fatty acid decarboxylation

All of these

Explanation

An anabolic pathway is a pathway in which smaller molecules are combined to form larger ones. This type of pathway usually requires energy to complete the combinations required. Photosynthesis is an example of this, because it combines carbon dioxide molecules to form glucose. The rest of the listed processes are catabolic pathways.

3

During the light-dependent reaction, the electron in                      is                      before the electron in                   .

photosystem II. . . excited. . . photosystem I

photosystem II. . . oxidized. . . photosystem III

photosystem I. . . removed. . . photosystem III

photosystem I. . . excited. . . photosystem II

Explanation

Contrary to their assigned numbers, the electron in photosystem II is excited before the electron in photosystem I. Their numbers are a reflection of the order in which they were discovered.

4

Which of the following is a product of photosynthesis?

Oxygen

Carbon dioxide

Hydrogen

Water

Nitrogen

Explanation

Photosynthesis is the biological process by which plants convert sunlight energy into chemical energy. The main product is the simple sugar glucose. The bonds in glucose can be broken and used for energy by the plants. The formula for photosynthesis is:

The reactants are carbon dioxide, water, and light energy. The products are glucose and oxygen.

5

Which of the following is a product of photosynthesis?

Oxygen

Carbon dioxide

Hydrogen

Water

Nitrogen

Explanation

Photosynthesis is the biological process by which plants convert sunlight energy into chemical energy. The main product is the simple sugar glucose. The bonds in glucose can be broken and used for energy by the plants. The formula for photosynthesis is:

The reactants are carbon dioxide, water, and light energy. The products are glucose and oxygen.

6

During the light-dependent reaction, the electron in                      is                      before the electron in                   .

photosystem II. . . excited. . . photosystem I

photosystem II. . . oxidized. . . photosystem III

photosystem I. . . removed. . . photosystem III

photosystem I. . . excited. . . photosystem II

Explanation

Contrary to their assigned numbers, the electron in photosystem II is excited before the electron in photosystem I. Their numbers are a reflection of the order in which they were discovered.

7

In the given chemical process, what does represent?

Carbohydrate

Carbon hydroxide

Chlorophyll

Carbonated water

Explanation

Carbohydrates are formed from carbon chains with a single oxygen group (either an aldehyde or a ketone). Carbohydrates have the general empirical formula . This formula can be used to designate a nonspecific carbohydrate molecule.

The process described is the conversion of light energy to chemical energy through photosynthesis. Chlorophyll serves as a functional pigment in this process, but is not involved in the net reaction. Carbonated water is formed from dissolved carbon dioxide in water, and is actually a solution of the two compounds. Carbon hydroxide is a misnomer, and does not refer to a real compound.

8

In the given chemical process, what does represent?

Carbohydrate

Carbon hydroxide

Chlorophyll

Carbonated water

Explanation

Carbohydrates are formed from carbon chains with a single oxygen group (either an aldehyde or a ketone). Carbohydrates have the general empirical formula . This formula can be used to designate a nonspecific carbohydrate molecule.

The process described is the conversion of light energy to chemical energy through photosynthesis. Chlorophyll serves as a functional pigment in this process, but is not involved in the net reaction. Carbonated water is formed from dissolved carbon dioxide in water, and is actually a solution of the two compounds. Carbon hydroxide is a misnomer, and does not refer to a real compound.

9

Some plants can fix carbon through an alternative pathway called the C4 pathway. What is the key advantage of the C4 pathway?

Fixing carbon with less water loss compared to C3 plants

Production of more RuBP to fuel the Calvin cycle

The combination of both C3 and C4 pathways allows the plant to grow faster

It provides a feedback mechanism to split more water during the light reaction

Explanation

The key characteristic of the C4 pathway is that is produces oxaloacetate and four-carbon sugars from carbon dioxide, compared to the Calvin cycle of most plants, which generates glyceraldehyde 3-phosphate and three-carbon sugars.

The C4 pathway fixes carbon dioxide into four-carbon compounds, thus the name. Pores on the plant called stomata regulate how much carbon dioxide, oxygen, and water enter and leave the plant and are usually partially closed during the hottest part of the day to conserve water. This yields a low carbon dioxide level and high oxygen level, which inhibits carbon fixation by the Calvin cycle. Plants that use the C4 pathway have an enzyme that can efficiently fix carbon to four-carbon compounds when the carbon dioxide level is low. The four-carbon compounds are then transported to other cells, where carbon dioxide is released and can enter the Calvin cycle.

Plants that use the C4 pathway are better adapted to hot and dry conditions, as they can fix carbon with less loss of water. Examples of C4 plants are corn and crabgrass.

10

What is the function of rubisco during the Calvin cycle?

It catalyzes the carboxylation of RuBP

It regenerates RuBP

It produces G3P molecules

It carries the prepared glucose to surrounding cells

It captures photons and uses them to generate ATP

Explanation

Rubisco is an enzyme that helps add carbon dioxide to RuBP molecules. This in turn forms an unstable inermediate compound, which immediately breaks into two 3-PGA molecules.

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