Biology: Breathing and Cellular Respiration

Breathing and Gas Exchange

Breathing refers to the mechanical process of pulling air into the lungs (inhalation) and expelling air out of the lungs (exhalation).
The primary organs of breathing, the lungs, are found in the thoracic cavity surrounded and protected by the rib cage.
At the end of the bronchioles in the lungs are tiny air sacs known as alveoli where gas exchange occurs - this is where oxygen from inhaled air passes into the blood, and carbon dioxide in the blood passes out into the lungs to be exhaled.
This transfer of gases is possible due to the thin walls of the alveoli and the rich supply of blood vessels, creating a gradient of concentration that facilitates diffusion of gases.

Cellular respiration is the process whereby cells obtain energy from the molecules of food like glucose and oxygen.
The process involves glycolysis, the Krebs Cycle, or Citric Acid Cycle and Oxidative Phosphorylation, which produces carbon dioxide as a waste product.
Glycolysis is the breakdown of glucose in the cell’s cytoplasm, which results in two molecules of pyruvate and generates a small amount of energy.
The Krebs Cycle and Oxidative Phosphorylation occur within the mitochondria, where the majority of the energy is extracted from glucose.
The overall process of cellular respiration yields adenosine triphosphate (ATP), which is energy currency for the cells.

The oxygen needed for cellular respiration comes from the air breathed in, diffuses from the lungs into the bloodstream, and is then transported to the cells where it is needed.
The waste product of respiration, namely carbon dioxide, is transported in the blood from the cells back to the lungs, where it is expelled when we exhale.
Breathing and cellular respiration are therefore interconnected - the primary reason we breathe is so that our cells can perform respiration, and the primary reason our cells perform respiration is to provide energy for the body’s functions.
Cellular respiration maintains the concentration gradient that allows oxygen to be absorbed and carbon dioxide to be expelled during the gas exchange process in the lungs.

The heart and circulatory system also play a key role in this process, as the blood and blood vessels transport oxygen to the cells and CO2 waste away from the cells, facilitating continual cellular respiration.
The red blood cells, specifically, have a protein called haemoglobin that binds to the oxygen and ensures its efficient transport to all cells in the body.
The plays a vital role in removing carbon dioxide waste and routing it back to the lungs to be exhaled.