The nutrients in the food we eat are broken down into smaller molecules during digestion. These smaller molecules are then absorbed into the bloodstream and transported throughout the body to be used by cells for energy, growth, and repair.
Once in the bloodstream, the nutrients are carried by red blood cells to the body's cells. The cells take up the nutrients they need and use them to produce energy or build new molecules. The process of transporting nutrients from the bloodstream into cells is called cellular respiration.
The body has an elaborate system of organs and tissues that work together to break down food, absorb nutrients, and transport them to cells throughout the body. The digestive system is responsible for breaking down food into smaller molecules, while the circulatory system is responsible for transporting these molecules to cells throughout the body.