Chloroplast Structure and Function

The chloroplast contains specialized compartments for different phases of photosynthesis. The light-dependent reactions occur in the thylakoid membrane while the Calvin Cycle takes place in the stroma.

Example: The electron transport chain components include Photosystem II, cytochrome complex, and Photosystem I, arranged in the thylakoid membrane.

Highlight: Ferredoxin-NADP+ reductase (FNR) catalyzes the final step in producing NADPH.

The process of carbon fixation through RuBisCO enzyme converts CO₂ into 3-PGA, which is then reduced to G3P using ATP and NADPH.

Light-Dependent Reactions and Water Splitting

The light-dependent phase of photosynthesis involves several key processes including water splitting and electron transport.

Definition: Chemiosmosis is the process where H+ ions create a gradient in the thylakoid lumen, driving ATP synthesis.

Vocabulary: The oxygen-evolving complex splits water molecules into H+, electrons, and O₂.

Highlight: The photosynthesis equation (CO₂ + H₂O → CH₂O + O₂) summarizes the overall process of converting light energy to chemical energy.

The excited electrons from chlorophyll molecules travel through the electron transport chain, ultimately reducing NADP+ to NADPH while simultaneously generating ATP through chemiosmosis.

Calvin Cycle and Carbon Fixation

The Calvin Cycle represents the light-independent phase of photosynthesis, involving three main stages: carbon fixation, reduction, and regeneration.

Definition: The Calvin Cycle is a series of biochemical reactions that produces glucose using energy from ATP and NADPH.

Highlight: G3P (Glyceraldehyde 3-phosphate) is the primary product that exits the cycle to form glucose.

Vocabulary: RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the key enzyme catalyzing carbon fixation.

The cycle requires 6 ATP and NADPH molecules for each complete turn, demonstrating the high energy requirements of photosynthesis.