Cellular Respiration II - Photosynthesis

What are the two main phases of photosynthesis?

Light-dependent reactions and the Calvin cycle (light-independent reactions).

Which pigment is primarily responsible for capturing light energy in plants?

Chlorophyll

What is the name of the enzyme that catalyzes carbon fixation in the Calvin cycle?

Rubisco.

What are the names of the two types of photosystems involved in the light reactions?

Photosystem I (P700) and Photosystem II (P680).

Where does the Calvin cycle take place in the chloroplast?

In the stroma.

How is ATP produced during the light-dependent reactions of photosynthesis?

Through chemiosmosis, as H+ ions flow through ATP synthase, driving the phosphorylation of ADP to ATP.

Why do plants have multiple types of photosynthetic pigments?

To absorb a broader range of the light spectrum, increasing efficiency in capturing light energy.

How does the structure of the thylakoid membrane contribute to its function?

It houses the photosystems and ETC, enabling light absorption, electron transport, and ATP synthesis.

What role does NADPH play in the Calvin cycle?

It provides the reducing power (electrons) needed to convert CO2 into G3P.

Why is photorespiration considered wasteful in C3 plants?

Because it consumes ATP and O2 without producing sugar.

A scientist mutates a plant gene that disrupts the enzyme that splits water in the thylakoid. What will most likely happen to the plant’s photosynthesis process?

The plant will not produce O2, electrons for the ETC will be absent, and ATP/NADPH synthesis will be impaired, halting the Calvin cycle.

You examine two plants under the same hot, dry conditions. One continues to photosynthesize efficiently, while the other exhibits slowed sugar production. What can you infer about the two plants?

The efficient plant is likely a C4 or CAM plant adapted to such conditions, while the other is a C3 plant experiencing photorespiration.

A plant is placed under green light for 48 hours. What changes would you expect in its photosynthesis rate?

Photosynthesis would decrease significantly since chlorophyll reflects green light and absorbs very little of it.

In a mutation, a plant’s chlorophyll a in Photosystem I is replaced with a pigment that absorbs only red light. How might this affect the plant?

Light absorption would be limited, reducing the efficiency of light reactions and decreasing ATP/NADPH production.

A plant is found to open its stomata only at night and stores CO2 as a 4-carbon compound. During the day, its stomata remain closed. What type of plant is this, and why is this adaptation beneficial?

It is a CAM plant. This adaptation reduces water loss in arid conditions while allowing photosynthesis to proceed during the day.