Once we digest foods in our stomach, this substance is then moved to the small intestine where red blood cells pick up these protein molecules and bring it to other cells. Our cells then absorb these nutrients and use the mitochondria to make use of it and convert into energy (ATP).
Lipids are used for long term energy storage as fats in humans and oils in plants. Carbohydrates are used for short term energy storage because they can be transported easily. Hope this helps xx