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.
One ring of gala apple contains a total of 7 calories, one slice contains 9 calories, one oz contains 13 calories, 100 grams contains 52 calories, one cup sliced gala apple contains 57 calories. A medium sized apple available from Wal-Mart weighing around 154 grams contains a total of 80 calories. All the 80 calories present in this are obtained from carbohydrates. The total carbohydrate content in it is 22 grams, dietary fiber content in it is 5 grams and sugar content is 17 grams.