The light-dependent reactions of photosynthesis do not use carbon. They use light energy to split water molecules, producing oxygen and ATP (energy) as well as NADPH (an electron carrier).

The carbon used in photosynthesis comes from carbon dioxide, which is used in the light-independent reactions (Calvin cycle) to produce glucose.

Here's a simple breakdown:

* Light-dependent reactions: Use light energy to produce ATP and NADPH.

* Light-independent reactions (Calvin cycle): Use ATP and NADPH to convert carbon dioxide into glucose.