Concept 8.3

Summary:

- Calvin cycle is called a cycle because like the Krebs cycle in cellular respiration, the starting material is regenerated each time the process occurs.
- The starting material that gets regeneratedis a compound called RuBP, a sugar with five carbons.
- With each turn of the Calvin cycle, there are chemical inputs and outputs.
- Inputs are carbon dioxide from the ari and the ATP and NADPH produced by light reactions.
- Calvin cycle uses carbon from the carbon dioxide, energy from the ATP, and high-energy electrons and hydrogen ions from the NADPH.
- Output is an energy-rich sugar molecule.
- Plant cell uses G3P as the raw material to make glucose and other organic molecules it needs.
- The equation for photosynthesis is 6CO2+ 6H2O+->->->C6H12O6+6O2.
- Light reactions convert light energy to the chemical energy of ATP and NADPH.
- Light reactions uses the reactant water from the equation and release the product oxygen.
- The Calvin cycle, which takes place in the stroma, uses ATP and NADPH to convert carbon dioxide to sugar.
- By converting light energy to chemical energy, photosynthesis is the first step in the flow of energy through an ecosystem.
- Photosynthesis is the ultimate source of all the food you eat and all the oxygen you breathe.

Concept check:
1. What are the inputs and outputs of the Calvin cycle?
Input: carbon dioxide and the ATP and NADPH
Output: energy-rich sugar molecule.

2. Which stage of photosynthesis uses each reactant from the overall photosynthesis equation? Which stage generates each product from the overall photosynthesis equation?
Photosynthesis, electron transport chain

3. Why is the Calvin cycle called a cycle?
Because like the Krebs cycle in cellular respiration, the starting material is regenerated each time the process occurs.

4. What molecule is the direct product of photosynthesis? How is that molecule then used by plant cells?
Oxygen, producing it.