Respiration — Science, 11–13 years
Respiration is how cells release usable energy from food. It is not the same as breathing: breathing moves gases, while respiration is a chemical process happening inside cells.
What respiration does
Your cells need energy to move muscles, keep warm, repair tissue and send signals. In aerobic respiration, cells use glucose from food and oxygen to release this energy, producing carbon dioxide and water as waste products. The energy is released in small, controlled steps rather than as one sudden burst.
Why cells respire
Food contains stored chemical energy, but a cell cannot simply use a sandwich to power a muscle. Respiration breaks suitable food molecules into a form the cell can use for many jobs. Scientists separated respiration from breathing because air entering the lungs is only part of the story; the useful energy is released inside cells.
After a fast run
Imagine sprinting for 30 seconds. Step 1: muscles need more energy, so cells respire faster. Step 2: you breathe more deeply and your heart beats faster, bringing more oxygen and glucose to the muscles. Step 3: cells release more energy and make more carbon dioxide. Step 4: you breathe hard afterwards while the body returns to its usual balance.
Breathing is not respiration
It is easy to call breathing and respiration the same thing because both involve oxygen and exercise makes both happen faster. But breathing is the movement of air into and out of the lungs. Respiration is the chemical energy release in cells, and it can continue in a cell even when you are not consciously thinking about breathing.
Respiration in real life
Respiration helps explain why athletes train their heart, lungs and muscles, and why a lack of oxygen makes intense exercise difficult. Yeast uses respiration when making bread, although it can also release energy without oxygen and produce carbon dioxide. In hospitals, breathing and blood tests help show whether cells are receiving what they need.
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