micro 8.6 pt 2

What are photosystems?

Complexes of pigments and proteins that capture light energy.

What are the two photosystems involved in oxygenic photosynthesis?

Photosystem II (PSII) and Photosystem I (PSI).

Which photosystem functions first in the light reactions?

Photosystem II (PSII).

What happens when chlorophyll absorbs light?

Its electrons become energized.

What replaces the electrons lost from Photosystem II?

Electrons obtained by splitting water.

What process splits water during photosynthesis?

Photolysis.

What are the products of photolysis?

Electrons, hydrogen ions (H⁺), and oxygen (O₂).

Why is oxygen released during photosynthesis?

It is a byproduct of splitting water.

Where do energized electrons go after leaving Photosystem II?

Through an electron transport chain.

What is the purpose of the electron transport chain in photosynthesis?

To use electron energy to pump protons and generate ATP.

How is ATP produced during the light reactions?

By chemiosmosis through ATP synthase.

Which photosystem re-energizes electrons after the electron transport chain?

Photosystem I (PSI).

What is the final electron acceptor in the light reactions?

NADP⁺.

What molecule is produced when NADP⁺ accepts electrons?

NADPH.

What is the role of NADPH in photosynthesis?

It provides high-energy electrons for the Calvin cycle.

Which two molecules produced by the light reactions are used in the Calvin cycle?

ATP and NADPH.

What is the first step of the Calvin cycle?

Carbon fixation.

Which enzyme catalyzes carbon fixation in the Calvin cycle?

RuBisCO.

What does RuBisCO do?

It attaches carbon dioxide to an organic molecule to begin carbohydrate synthesis.

What is the primary product of the Calvin cycle?

G3P (glyceraldehyde-3-phosphate).

What can G3P be used to make?

Glucose and other carbohydrates.

What molecule is regenerated during the Calvin cycle so it can continue?

RuBP (ribulose bisphosphate).

Does the Calvin cycle require ATP?

Yes.

Does the Calvin cycle require NADPH?

Yes.

Why is the Calvin cycle sometimes called the light-independent reactions?

It does not use light directly, although it depends on ATP and NADPH produced by the light reactions.

What is cyclic photophosphorylation?

A pathway in which electrons cycle through Photosystem I to produce extra ATP but not NADPH or oxygen.

Why do cells use cyclic photophosphorylation?

To produce additional ATP when needed.

What is the major difference between cyclic and noncyclic photophosphorylation?

Noncyclic produces ATP, NADPH, and O₂; cyclic produces only ATP.

What is the overall goal of the light reactions?

To convert light energy into ATP and NADPH.

What is the overall goal of the Calvin cycle?

To use ATP and NADPH to convert CO₂ into carbohydrates.