Cellular respiration in animals is necessary to transfer the chemical energy from sugar obtained from their food into ATP for use throughout the body. Which two systems work together to transport the sugar from food to the cells in the organism's brain?

Two systems that work together to transport the sugar from food to the cells in the organism’s brain are digestive system and circulatory system.

All carbohydrates from the food are broken down into glucose via enzymes from the mouth and small intestine. Absorption of glucose occurs in the microvilli of epithelial cells (small intestine). From there, glucose is transported directly into the bloodstream. Also, pancreas secrets the hormone insulin which makes cell permeable for glucose (via transporters).