We all need energy to function and we get this energy from the foods we eat. The most efficient way for cells to harvest energy stored in food is through cellular respiration, a catabolic pathway for the production of adenosine triphosphate (ATP). ATP, a high energy molecule, is expended by working cells.
An Apple a Day. The calories in a McIntosh apple depend on its size. According to the U.S. Department of Agriculture, a medium-sized apple with its skin has about 95 calories. Eating an unpeeled apple is moderately higher in calories than a peeled apple, but don't rush to peel your apple.
Do apples give you more energy than a cup of coffee? It depends on how you look at energy. A medium apple contains about 100 calories and approximately 20 grams of sugar. The calorie elements in one apple includes protein, fats and carbohydrates like sugar and starch. Your body will process these nutrient molecules into adenosine triphosphate or ATP. ATP is literally fuel for your cells and they use it for everything they do that requires energy.