Photosynthesis occurs in 2 parts- The light reactions and the Calvin Cycle.

The light reactions CO 2 + H 2 O + light energy (CH 2 O) + O 2

The light cycle is dependent on light. Within the chloroplast, are sacs of organelles called thylakoids. (A stacked bundle of these are called Granum.)

The Thylakoids membranes contain chlorophyll. The chlorophyll is a pigment that absorbs the light from the sun

Steps of the light reactions.

1.)The light absorbed by chlorophyll causes a transfer of electrons and H + from H 2 0 molecules already present. This causes the H 2 0 to split into molecular 0xygen (0 2 ) and a H + ion.

2) The O 2 is released (we breathe it) and the H + bonds to NADP + creating NADPH

3) ATP is formed (ADP gets a phosphate group added to it creating ATP)

4)The NADPH and the ATP created here go on to fuel the reactions in the second part of photosynthesis

Steps of the Calvin Cycle 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 )+ 6O 2

The Calvin Cycle is the second stage of photosynthesis takes place in the stroma of the chloroplast can occur without the presence of sunlight.

carbon molecules from CO 2 are fixed into glucose (C 6 H 12 O 6 ) Process known as carbon fixation

Step 1 (simplified) 1) CO 2 comes into stroma from the cytosol 2) fixed with a 5 carbon molecule making a 6 carbon molecule 3) Gets split into two 3C molecules called PGA

Step 2 1)The 2 PGA molecules get phosphate from splitting of ATP 2)Forms PGAL (still only 3C), and most importantly 3)An organic molecule (like glucose)

Also forms ADP, NADP + and phosphate These can be used again in future light reactions

Step 3 Most PGAL converted back to a 5C molecule (remember the Calvin Cycle begins with a 5C molecule & one CO 2 molecule)