Photosynthesis makes the glucose that is used in cellular respiration to make ATP. ... While photosynthesis requires carbon dioxide and releases oxygen, cellular respiration requires oxygen and releases carbon dioxide. It is the released oxygen that is used by us and most other organisms for cellular respiration.
Pp is the genotype because you know purple must have a gene of purple, which it says is dominant. If the white is recessive, the purple with dominate the white.
