How do cells obtain energy?
The process that produces energy for the body to use is called cellular respiration.
ATP the energy source used by cells. ATP stands for adenosine triphosphate. ATP is produced during cellular respiration.
Cellular respiration can occur in the presence or absence of oxygen. However, much more energy is produced for the body when cellular respiration is completed in the presence of oxygen. In the presence of oxygen, 34-38 ATP are produced. In the absence of oxygen, the net yield of ATP produced is 2.
ATP is formed in the presence of oxygen during the process that is known as aerobic cellular respiration. This process occurs within mitochondria of eukaryotic cells. There are three main parts of aerobic cellular respiration- glycolysis, Krebs Cycle, and the electron transport chain. Overall, aerobic cellular respiration converts the sugar called glucose and oxygen gas into carbon dioxide gas, water, and 34-36 ATP.
Here, the processes that occur during each phase of aerobic cellular respiration can be read in greater detail.
Anaerobic respiration is sometimes referred to as fermentation. Fermentation is a metabolic process in which organisms convert carbohydrates, such as starch or sugar, into lactic acid or alcohol.
Ethanol fermentation is the type of fermentation that produces alcohol. It is done by yeast and some strains of bacteria. During ethanol fermentation, pyruvate from glucose metabolism is broken into ethanol and carbon dioxide. Because ethanol fermentation produces alcohol, it is used to produce beer and wine. The carbon dioxide produced by ethanol fermentation is advantageous in the making of breads.
During lactic acid fermentation, six-carbon carbohydrates, such as the pyruvate molecules from glycolysis or lactose, are converted into cellular energy (ATP) and lactic acid. Lactic acid occurs within muscle cells during intense intervals of activity when energy is needed at a faster rate than oxygen can be supplied. The lactic acid produced is the “burn” that athletes feel after an intense workout.