What process builds the carbon-based molecules?

Well they're considered buding blocks, organic compounds are all based on carbon. They have basic shapes, which are straight chain, branded chain, and ring

Hope this helps.

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.