Photosynthesis

Purpose of photosynthesis

To convert solar energy into chemical energy stored in glucose.

Overall equation for photosynthesis

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Organelle for photosynthesis

The chloroplast.

Two major stages of photosynthesis

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

Location of light-dependent reactions

In the thylakoid membranes.

Inputs of the light-dependent reactions

Light, water (H₂O), ADP, and NADP⁺.

Outputs of the light-dependent reactions

ATP, NADPH, and oxygen (O₂).

Role of chlorophyll

It absorbs light energy, especially in the blue and red wavelengths.

Water during light reactions

It is split (photolysis) to release electrons, protons (H⁺), and oxygen.

Role of NADP⁺ in photosynthesis

It acts as an electron carrier, becoming NADPH when reduced.

Enzyme for ATP synthesis

ATP synthase.

Chemiosmosis in photosynthesis

The use of a proton gradient to produce ATP in the thylakoid membrane.

Location of the Calvin cycle

In the stroma of the chloroplast.

Inputs of the Calvin cycle

CO₂, ATP, and NADPH.

Main output of the Calvin cycle

Glucose (C₆H₁₂O₆).

Molecule CO₂ combines with in Calvin cycle

RuBP (ribulose bisphosphate).

Enzyme for carbon fixation

Rubisco.

Why is the Calvin cycle light-independent?

It doesn’t require light directly but depends on ATP and NADPH from the light reactions.

Thylakoids

Membrane-bound sacs in the chloroplast where light reactions occur.

Stroma

The fluid-filled space around the thylakoids where the Calvin cycle takes place.