ANATOMY

Detailed explanation-1: -Cellular respiration is a chemical process in which food molecules are broken down into simpler molecules within the cells and energy is produced. In cellular respiration, the inhaled oxygen is used for breaking the food. Hence in respiration oxygen is required and carbon dioxide is released out.

Detailed explanation-2: -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. We breathe in that oxygen, which is carried through our blood to all our cells.