Page 2: The Calvin Cycle - Light-Independent Reactions

The second page delves into the light-independent reactions of photosynthesis, also known as the Calvin cycle or faza ciemna fotosyntezy. This phase occurs in the stroma of chloroplasts and does not directly require light.

Definition: The Calvin cycle is a series of biochemical reactions that use the products of the light-dependent reactions to fix carbon dioxide into glucose.

The page presents a detailed diagram of the Calvin cycle, which consists of three main stages:

1. Carbon Fixation (Carboxylation): CO₂ is added to ribulose-1,5-bisphosphate (RuBP) to form an unstable 6-carbon compound that splits into two 3-carbon molecules.

Vocabulary: RuBP (Ribulose-1,5-bisphosphate) is the CO₂ acceptor molecule in the Calvin cycle.

2. Reduction: The 3-carbon compounds are reduced using ATP and NADPH from the light-dependent reactions to form 3-phosphoglyceraldehyde (PGAL).

3. Regeneration: Some of the PGAL molecules are used to regenerate RuBP, completing the cycle.

Highlight: For every three CO₂ molecules fixed, one PGAL molecule is produced as the net gain, which can be used to synthesize glucose and other organic compounds.

The diagram also shows the energy requirements of the cycle:

• 6 ATP molecules are used in the regeneration phase
• 12 ATP and 12 NADPH molecules are used in the reduction phase

Example: The Calvin cycle is a perfect demonstration of how the products of the light-dependent reactions (ATP and NADPH) are utilized in the light-independent reactions to fix carbon dioxide.

This page provides a comprehensive visual representation of the przebieg fotosyntezy, specifically focusing on the faza ciemna fotosyntezy etapy (stages of the dark phase of photosynthesis).