We breathe to bring oxygen into the body so cells can make energy, and to get rid of carbon dioxide waste that would otherwise poison us and disturb our blood’s pH balance. Without this constant gas exchange, our cells quickly fail and we lose consciousness and die.

What breathing actually does

  • With each inhale, air reaches the lungs, where oxygen passes into tiny blood vessels (capillaries) and enters the bloodstream.
  • Hemoglobin in red blood cells carries this oxygen to cells all over the body, where it is used to release energy from food (cellular respiration) in the form of ATP.
  • Cells produce carbon dioxide as a waste gas, which dissolves in the blood and is carried back to the lungs to be exhaled.

Why oxygen is so important

  • Cells “burn” nutrients with oxygen in a series of chemical reactions to make ATP, the energy currency that powers movement, thinking, growth, and repair.
  • If oxygen supply stops, ATP production collapses within minutes, especially in the brain and heart, leading quickly to loss of function and death.

Why we must remove carbon dioxide

  • Carbon dioxide in blood forms carbonic acid and makes the blood more acidic, so levels must be tightly controlled.
  • The urge to breathe is driven more by rising carbon dioxide and acidity than by falling oxygen, which is why holding your breath soon becomes very uncomfortable.

How the body controls breathing

  • Sensors in blood vessels and the brainstem constantly monitor oxygen, carbon dioxide, and pH, adjusting breathing rate and depth to match the body’s activity.
  • During exercise, breathing can increase many times over to deliver more oxygen to working muscles and to prevent carbon dioxide from building up.

Big-picture view

  • Breathing keeps the body’s internal environment stable: oxygen in, carbon dioxide out, pH in a narrow safe range.
  • In that sense, breathing is the visible part of a deeper process—cellular respiration—that keeps every living cell in the body alive and working from moment to moment.

Information gathered from public forums or data available on the internet and portrayed here.