In your own words describe the two major reactions of photosynthesis, where they occur and the inputs and outputs AND summarise the information in the table below. Outputs Location (organelle and place Inputs within) Light dependent reactions Light independent reactions (Calvin cycle)
The Correct Answer and Explanation is :
Explanation of Photosynthesis Reactions
Photosynthesis consists of two main stages: light-dependent reactions and the light-independent reactions (Calvin cycle). These processes occur in chloroplasts and work together to convert light energy into chemical energy stored in glucose.
1. Light-Dependent Reactions
- Location: Thylakoid membranes in chloroplasts.
- Inputs: Light energy, water (H₂O), and ADP + inorganic phosphate (Pi), NADP⁺.
- Outputs: Oxygen (O₂), ATP, and NADPH.
- Process:
When sunlight strikes chlorophyll molecules in the thylakoid membranes, energy excites electrons. Water molecules are split (photolysis), releasing oxygen as a byproduct. The excited electrons travel through the electron transport chain, generating ATP via photophosphorylation and reducing NADP⁺ to NADPH, both of which store energy for the Calvin cycle.
2. Light-Independent Reactions (Calvin Cycle)
- Location: Stroma of chloroplasts.
- Inputs: ATP, NADPH, and carbon dioxide (CO₂).
- Outputs: Glucose (C₆H₁₂O₆), ADP + Pi, and NADP⁺.
- Process:
This cycle does not require light but depends on the ATP and NADPH from the light-dependent reactions. CO₂ is fixed into a 5-carbon sugar (RuBP) by the enzyme Rubisco. The cycle involves three main phases: carbon fixation, reduction, and regeneration of RuBP. Energy from ATP and NADPH transforms CO₂ into glucose.
Table Summary:
| Outputs | Location (Organelle & Place) | Inputs |
|---|---|---|
| Light-Dependent Reactions | Thylakoid membranes (chloroplast) | Light, water (H₂O), ADP + Pi, NADP⁺ |
| Light-Independent Reactions | Stroma (chloroplast) | ATP, NADPH, carbon dioxide (CO₂) |
300-Word Explanation
Photosynthesis is a two-step process essential for life, converting sunlight into glucose, a usable form of chemical energy.
The light-dependent reactions, occurring in the chloroplast’s thylakoid membranes, require light. Here, chlorophyll absorbs sunlight, exciting electrons. Water molecules split, releasing oxygen gas. The energy from electrons drives ATP production and converts NADP⁺ into NADPH, both essential for the next stage.
The Calvin cycle occurs in the stroma, the chloroplast’s fluid-filled space. Using ATP and NADPH generated earlier, it fixes atmospheric CO₂ into organic molecules. Through a series of steps, these molecules transform into glucose, while ADP and NADP⁺ are recycled for reuse in the light-dependent stage.
This integration of light and dark reactions ensures a sustainable energy flow, highlighting the elegance of nature’s energy transformation systems.