Photosynthesis occurs in 2 sets of main reactions in the chloroplast.
1. Light Reactions (Occurs in Grana)
The purpose of the light reactions is to change light energy into chemical energy of ATP and NADPH.
a) Require light
b) Light makes excited electrons leave the chlorophyll. The electrons pass their energy to make ATP.
c) The light splits water to make hydrogen ions (H+) and oxygen.
d) The oxygen is released to the air.
e) The H+ and more excited electrons are used to make NADPH (an energy & H+ carrier).
ATP carries energy to the dark reactions.
NADPH carries energy and H+ to the dark reactions.
2. Dark Reactions (Occurs in Stroma)
The purpose of the dark reactions is to change CO2 into sugar by adding energy & the H+ from ATP & NADPH.
a) Can occur in light or dark.
b) 6 CO2 & lots of ATP & NADPH are needed to make one sugar molecule.
c) The sugar is then used for plant growth or stored for use in the winter (so we can eat it!)