Why is there a difference between the macromolecules we eat and what is in our body

For example, macromolecules provide structural support, a source of stored fuel, the ability to store and retrieve genetic information, and the ability to speed biochemical reactions. Four major types of macromolecules—proteins, carbohydrates, nucleic acids, and lipids—play these important roles in the life of a cell.

Explanation:

For example, macromolecules provide structural support, a source of stored fuel, the ability to store and retrieve genetic information, and the ability to speed biochemical reactions. Four major types of macromolecules—proteins, carbohydrates, nucleic acids, and lipids—play these important roles in the life of a cell.

i have to report this, it doesn't relate to biology

protocol for imps extraction focusing on membrane protein extraction, solubilisation, and purification.