Final answer:
Haemoglobin is the key protein in red blood cells that is responsible for transporting oxygen throughout the body. It binds oxygen to iron within its structure, allowing each molecule to carry up to four oxygen molecules, making it highly efficient for oxygen distribution in the bloodstream.
Step-by-step explanation:
The cellular component that is responsible for carrying oxygen in the blood is haemoglobin. Hemoglobin is a metalloprotein within red blood cells, also known as erythrocytes, and is essential for oxygen transport in the bloodstream. It is made up of four subunits and heme groups, with each heme group containing an iron ion that can bind to oxygen molecules.
The binding of oxygen to haemoglobin forms oxyhemoglobin, which is responsible for the characteristic bright red colour of oxygenated blood. Furthermore, each haemoglobin molecule can bind up to four oxygen molecules, enabling the efficient transport of oxygen from the lungs to body tissues. Moreover, red blood cells carry approximately 250 million molecules of haemoglobin, with each cell being capable of transporting around one billion oxygen molecules.
Haemoglobin also plays a role in carrying carbon dioxide, a waste product of metabolism, from the body's tissues back to the lungs where it can be exhaled. The ability of erythrocytes to carry such a large quantity of oxygen—up to 25 sextillions (25 × 10²¹) molecules within the typically five litres of blood in a human body—is crucial for sustaining life and supporting the body's various functions.