Question

-!!! Three Medal Question !!!

- Describe the chloroplast and its role in photosynthesis.

- Summarize what happens during the light reactions of photosynthesis.

What happens during the carbon fixation step of the Calvin cycle?

Answer 1

The chloroplast is an organelle composed of stacks of thylakoids, which contain chlorophyll, surrounded by a fluid matrix called the stroma. The chloroplast is responsible for capturing sunlight(chlorophyll does this), initially, and beginning the light reactions. During the light reactions water is split by the excited electrons from the absorption of sunlight. Excited electrons and the H+ ions from the water are used in photosystem II and I to produce ATP and NADPH. The electron transport chain is the mechanism by which these molecules are produced. Also produced during the light reactions is O2 which is given off as a by-product. CO2 fixation is the first part of the Calvin cycle where CO2 is combined with RuBP to produce an unstable 6C molecule that breaks down to form 2 three carbon molecules called PGA or phosphoglyceric acid.