The energy-rich compound needed by organism is : Carbohydrates
Carbohydrates consist of the combination of the existing Carbon, Hydrogen, and Oxygen alone.
For human, The source of carbohydrates could be found in almost every food, but the huge amount could be found in rice, potato, corn, cassava, oatmeal, etc
hope this helps
You see, passive transport needs no energy. So that being said, it moves from areas with high concentration to areas with low concentration.
Hope that helps!
