Fundamentals of Cellular Respiration and Oxygen Use

Notes

A baby’s first cry! This sound shows that the baby is breathing and taking in oxygen. But why is oxygen necessary for life? Oxygen is a reactant in cellular respiration—the process that breaks down food molecules and generates ATP, the energy currency of cells. Cellular respiration also produces heat, which helps maintain a constant body temperature. When exposed to the cold, a newborn can’t keep herself warm. Newborns lack the ability to shiver, a process that generates heat by rapid muscle contraction. Instead, infants rely on a special layer of “baby fat,” called brown fat. Brown fat cells have a “short circuit” in their cellular respiration—they consume oxygen, but generate heat instead of ATP. Recent studies indicate that in adults, brown fat plays a different role and could be targeted in the fight against obesity (see Module 6.12). In this chapter, we explore the stages of cellular respiration and how cells produce ATP in the presence of oxygen. We also consider how cells produce energy under anaerobic conditions—the absence of O2. As you will discover, not all cells need oxygen to produce energy, but all cells require a mechanism for producing ATP. A baby’s first cry! This ...