Concept 8.3 Summary

A cycle=a process in which the starting material is regenerate each time the process occurs.

*The Calvin Cycle=RuBP, the starting material of the process, gets regenerated.

The Calvin Cycle

-input (reactant)=carbon (CO2), energy (ATP), high-energy electrons and hydrogen ions (NADPH)

-output (product)=G3P (energy-rich sugar molecule)

*The plant cell uses G3P as the raw material to make glucose and other organic molecules.

-steps:

(1) 3 carbon molecules (3CO2) enters the cycle, then combines with 3 RuBP molecules, producing 3 six-carbon molecules,

(2) 3 six-carbon molecules break down into 6 three-carbon molecules (3-PGA),

(3) ATP and NADPH from light reactions provide energy and electrons. It results 6 3-PGA

changing into 6 G3P (direct product of photosynthesis),

(4) Carbon (G3P) exits the cycle,

(5) 5 G3P (containing 15 carbon atoms) left in the cycle,

(6) ATP provides energy. It results G3P changing into RuBP,

ADP and NADP+ return to light reactions.

Photosynthesis Summary

-The Light Reactions:

-takes place in the thylakoid membranes

-converts light energy to the chemical energy of ATP and NADPH

-reactant: water

product: oxygen

-The Calvin Cycle:

-takes place in the stroma

-reactant: carbon dioxide

product: sugar (G3P) * uses ATP and NADPH from the light reactions.

Concept Check 8.3

1. Where are the inputs and outputs of the Calvin cycle?

The inputs are carbon dioxide, ATP and NADPH.

The outputs are sugar molecules (G3P).

2. Which stage of photosnthesis uses each reactant from the overall photosynthesis equation? Which stage generates each product from the overall photosynthesis equation?

The light reactions use water, and generate oxygen.

The Calvin Cycle uses carbon dioxide, and generates sugar (glucose).

3. Why is the Calvin cylce called a cycle?

Because it has a starting material, RuBP (a sugar with five carbons), that gets regenerated each time the Calvin cycle process occurs.

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

The direct product of photosynthesis is G3P. It is used by plant cells to make glucose and other organic compounds.