Oxygen Transport in the Human Body
In aerobic cells and organisms (including humans), oxygen is essential for life. This diatomic gas participates in a number of processes in individual cells, processes that create and store energy. This vital substance must be available to each aerobic cell in order for it to function, leading to the requirement of specialised oxygen transport systems in large organisms.
Section 1.0 – The Role of The Lungs
In small organisms, the external surface area of their bodies are sufficient to provide an oxygen diffusion gradient to the volume of cells in their bodies. However, the human surface area to volume ratio is very low. As a result, humans require a specialized surface for gas exchange to take place. This surface is the lung. Each lung provides a tremendous amount of surface area for gas exchange due to their fractal structure. As well, a gas exchange surface must be kept moist in order for the oxygen to diffuse across into the transport system. The lungs use a substance called surfactant in order to achieve this. Each alveolus in the lung is surrounded by a large capillary network which accepts the diffused oxygen into red blood cells, and transports it through the body.
Section 2.0 – Haemoglobin
Inside of each red blood cells are large quaternary proteins known as haemoglobin, so named because they contain iron hemes that bind to oxygen atoms. When oxygen diffuses into a red blood cell, the high oxygen-affinity of haemoglobin causes it to bind to the iron hemes. It is mostly in these proteins that oxygen is carried through the body.
Section 3.0 – Myoglobin
Myoglobin is found in muscles in the body. These proteins have a higher affinity for oxygen than haemoglobin, effectively making them a stored oxygen supply. The muscles require this as they need to maintain higher levels of activity than the haemoglobin in the blood can provide in a short time.
Section 4.0 – Dissociation
Blood in which CO2 – a waste product of respiration – is dissolved is more acidic than oxygenated blood. This acidity triggers the release of oxygen from the haemoglobin, forming haemoglobinic acid. This is known as haemoglobin dissociation. This allows areas that are respiring to receive a larger amount of oxygen, as their waste product stimulates the release.
Oxygen transport systems are vital to large organisms, including humans. These systems allow required oxygen to reach sites where respiration occurs, creating energy. Substances such as haemoglobin and myoglobin increase the efficiency and effectiveness of the oxygen transport system, allowing the survival of large species, in this case the human being.