Respiration (noun, “RES-per-a-shun”)
Respiration has different meanings, depending on where it takes place. In our lungs, respiration can refer to the act of breathing. If you breathe in and out 20 times per minute, you have 20 respirations per minute.
It also refers to what happens when we breathe in and out. Respiration describes how oxygen moves into our cells and carbon dioxide moves out. This transfer of oxygen and carbon dioxide occurs when we breathe.
But within cells, respiration means something else. Cellular respiration is a chemical process that takes place inside cells and produces energy. The process breaks bonds in sugars. Breaking those bonds releases the energy they contain. That energy gets stored in molecules called ATP. That stands for adenosine triphosphate. These ATP molecules act as tiny chemical batteries, carrying the energy to places in the cell that need it.
Cellular respiration is often aerobic. That means it requires oxygen and makes carbon dioxide as a waste product. But cells can also perform anaerobic respiration, or making energy without oxygen, if they have to. Some kinds of bacteria are so good at anaerobic respiration that they don’t bother with oxygen at all.
In a sentence
With a combination of aerobic and anaerobic respiration, Cuvier’s beaked whales can stay underwater for up to four hours.