Living cells need a constant supply of oxygen and nutrients - Edexcel - GCSE Biology - Question 6 - 2016 - Paper 1

Oxygen is primarily transported in the blood by binding to hemoglobin, a protein found in red blood cells. The binding occurs in the lungs, where oxygen diffuses from the alveoli into the bloodstream and attaches to hemoglobin molecules.

Once attached, the oxygen is carried through the bloodstream via the circulatory system. The heart plays a crucial role by pumping this oxygen-rich blood through named blood vessels, such as arteries.

As the blood circulates, the oxygen is delivered to tissues and cells throughout the body, where it is finally released to be used in cellular respiration.