Photosynthesis

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AP Biology › Photosynthesis

Questions 1 - 10
1

Which is not a step of the light independent reaction?

carbon fixation

regeneration of RuBP

production of G3P

light absorption in photosystem II

Explanation

Absorption of sunlight in photosystem II is the first step of the light dependent reaction, not the light independent reaction. During the light independent reaction, or the Calvin Cycle, carbon fixation first occurs. CO2 produced during the light dependent reaction reacts with RuBP, ultimately producing PGA. This reaction is catalyzed by the enzyme Rubisco. Then, PGA is converted to G3P, using ATP and NADPH produced during the light dependent reaction. The G3P is ultimately converted to glucose. Every 3 cycles of the Calvin Cycle (light independent reaction), 6 molecules of G3P are produced; only 1 is used to produce glucose. The remaining 5 molecules of G3P are used to regenerate RuBP to allow the Calvin Cycle to continue.

2

Where does the Calvin Cycle take place?

Stroma

Thylakoid membrane

Mitochondrial lumen

Cytoplasm

Chloroplast outer membrane

Explanation

The Calvin Cycle (dark reactions) take place in the stroma of the chloroplasts, which is the aqueous space inside the organelle.

3

Which is not a step of the light independent reaction?

carbon fixation

regeneration of RuBP

production of G3P

light absorption in photosystem II

Explanation

Absorption of sunlight in photosystem II is the first step of the light dependent reaction, not the light independent reaction. During the light independent reaction, or the Calvin Cycle, carbon fixation first occurs. CO2 produced during the light dependent reaction reacts with RuBP, ultimately producing PGA. This reaction is catalyzed by the enzyme Rubisco. Then, PGA is converted to G3P, using ATP and NADPH produced during the light dependent reaction. The G3P is ultimately converted to glucose. Every 3 cycles of the Calvin Cycle (light independent reaction), 6 molecules of G3P are produced; only 1 is used to produce glucose. The remaining 5 molecules of G3P are used to regenerate RuBP to allow the Calvin Cycle to continue.

4

Where does the Calvin Cycle take place?

Stroma

Thylakoid membrane

Mitochondrial lumen

Cytoplasm

Chloroplast outer membrane

Explanation

The Calvin Cycle (dark reactions) take place in the stroma of the chloroplasts, which is the aqueous space inside the organelle.

5

Plants are an example of which of the following categories of organisms?

Autotrophs

Heterotrophs

Chemoautotrophs

Biosphere consumers

Explanation

Plants are an example of autotrophs. Autotrophs sustain themselves without consuming other organic material. Instead they create organic material from inorganic materials.

6

Plants are an example of which of the following categories of organisms?

Autotrophs

Heterotrophs

Chemoautotrophs

Biosphere consumers

Explanation

Plants are an example of autotrophs. Autotrophs sustain themselves without consuming other organic material. Instead they create organic material from inorganic materials.

7

What are the products of photosynthesis?

Glucose and oxygen

Water and carbon dioxide

Carbon dioxide and light

Light and glucose

Oxygen and carbon dioxide

Explanation

The photosynthesis equation can be written as:

From this equation, we can see that plants take in carbon dioxide, water, and light energy as reactants and produce glucose and oxygen as products.

8

Where does the Calvin cycle take place in the chloroplasts?

Stroma

Thylakoid

Mitochondria

Nucleus

Explanation

The Calvin cycle takes place in the stroma area in the chloroplasts. The mitochondria is another organelle, and the nucleus contains the DNA. The thylakoids are in the chloroplasts and contain the pigment chlorophyll in which the light reactions occur.

9

What are the products of photosynthesis?

Glucose and oxygen

Water and carbon dioxide

Carbon dioxide and light

Light and glucose

Oxygen and carbon dioxide

Explanation

The photosynthesis equation can be written as:

From this equation, we can see that plants take in carbon dioxide, water, and light energy as reactants and produce glucose and oxygen as products.

10

Where does the Calvin cycle take place in the chloroplasts?

Stroma

Thylakoid

Mitochondria

Nucleus

Explanation

The Calvin cycle takes place in the stroma area in the chloroplasts. The mitochondria is another organelle, and the nucleus contains the DNA. The thylakoids are in the chloroplasts and contain the pigment chlorophyll in which the light reactions occur.

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