AP BIOLOGY

Detailed explanation-1: -This energy is derived from the chemical bond energy in food molecules, which thereby serve as fuel for cells. Sugars are particularly important fuel molecules, and they are oxidized in small steps to carbon dioxide (CO2) and water (Figure 2-69).

Detailed explanation-2: -Food energy is expressed in calories or joules. A calorie is the amount of energy required at one atmosphere of pressure to raise the temperature of 1 g of water from 14.5°C to 15.5°C (NRC, 1981).

Detailed explanation-3: -Through the process of cellular respiration, the energy in food is converted into energy that can be used by the body’s cells. During cellular respiration, glucose and oxygen are converted into carbon dioxide and water, and the energy is transferred to ATP.