| Term | Definition |
| calorie | amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius |
| glycolysis | first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid |
| cellular respiration | process that releases energy by breaking down glucose and other food molecules in the presence of oxygen |
| NAD+ | electron carrier involved in glycolysis |
| fermentation | process by which cells release energy in the absence of oxygen |
| anaerobic | process that does not require oxygen |
| aerobic | process that requires oxygen |
| Krebs cycle | second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions |
| electron transport chain | a series of proteins in which the high-energy electrons from the Krebs cycle are used to convert ADP into ATP |