Bio 3 - Transporting Substances around the Body - Transport in the Blood

Your blood is a mixture of liquid and cells which carries a large range of substance around the body. The liquid part is called the Plasma. It carries Red Blood Cells, White Blood Cells and Platelets.

White Blood Cells are part of your immune system, which is your defence agaist disease. The Platelets are involved in the clotting of blood. The Blood Plasma and the Red Blood Cells which are involved in the transport of materials around the body

Blood Plasma is a yellow liquid - the red colour of the whole blood comes from the Red Blood Cells. The Plasma transports all of your blood cells and a number of other things around your body. CO2 produced in organs of the body is carried back to the lungs in the Plasma.

In Urea, a waste product formed in your liver from the breakdown of proteins, is carried in the Plasma to your Kidneys. In the Kidneys the urea is removed from your blood to form urine.

All the small Soluble products of digestion pass into your blood from the gut. They are carried in the Plasma around your body to the organs and cells that need them.

There are more Red Blood Cells than any other type of blood cell in your body. You have about 5 million of them per 1mm^3 of your blood - and the average person has between 4.7 - 5.0 litres of blood in their body.

They pick up oxygen from your lungs and carry it to the tissues and cells where it is needed. Your Red Blood Cells have a number of adaptations which make them efficient:

- They have an unusual shape, they are Bioconcave Discs. This means they are Concave (Pushed in) on Both sides. (Giving them an increased Surface Area : Volume ratio over which diffusion of oxygen can take place

- They are packed full of special red pigment called haemoglobin, which can carry oxygen

- They don't have a nucleus, leaving more space for haemoglobin

Haemoglobin is a large protein molecule folded around four iron atoms.

In a high concentration of oxygen, such as in the lungs, the haemoglobin reacts with the oxygen to form oxyhaemoglobin.

This is bright scarlet in colour, which is why the blood in most of your arteries is bright red

In areas where the concentration is lower, such as the cells and organs of the body, the reaction reverses. The oxygen diffuses into the cells where it is needed. Haemoglobin is purply red - The colour of blood in the veins

Because haemoglobin is based on iron, if your diet lacks in it, your body can not make enough Red Blood Cells and you suffer from Anaemia. 

People who are anaemic are pale and lack energy. Thats because they cannot carry enough oxygen around the body.