1. Chapter 30: Blood Leaving Certificate Biology Higher Level

2. Composition of Blood Blood has four main components: –Plasma –Red blood cell (erythrocytes) –White blood cells (leucocytes) –Platelets (thrombocytes)

3. Composition of Blood (cont.) Plasma: –The fluid of the blood making up ~55% of the blood volume –Composed mainly of water with some protein and other dissolved solutes –Plasma proteins include: Antibodies Clotting proteins Hormones

4. Composition of Blood (cont.) Red blood cells: –Contain protein called haemoglobin – which is responsible for carrying oxygen –Made in the bone marrow of long bones –Have no nucleus (anuclear) – and so cannot repair themselves and have no mitochondria –Survive for ~120 days (4 months) and are then broken down by the liver – iron from haemoglobin can be reused –Are biconcave in shape to give more surface area for diffusion of oxygen

5. Composition of Blood (cont.) Red blood cells (cont.): –Haemoglobin of the red blood cells is a protein that has great affinity for oxygen –Haemoglobin has a iron atom at its centre –In the oxygen-rich lungs, four oxygen molecules attach to the haemoglobin molecule to form oxyhaemoglobin due to the concentration gradient between the lumen of the alveoli and the bloodstream –In the tissues oxygen is given up readily by haemoglobin and diffuses into the oxygen-poor tissue due to the concentration gradient between the red blood cell and the tissue

6. Composition of Blood (cont.) White blood cells (leucocytes): –Made in the bone marrow and mature in the lymphatic system –Much larger than red blood cells and contain a nucleus that takes up most of the volume of the cell –No definite shape –Responsible for fighting infection –Classified into lymphocytes and monocytes Lymphocytes respond to infection by the production of antibodies Monocytes mature into macrophages and engulf bacteria, viruses and foreign material

7. Composition of Blood (cont.) Platelets (thrombocytes): –They are cell fragments made in the bone marrow from large cells called megacytes –Function in blood clotting by sticking to damaged internal epithelial cells –In doing this they: prevent blood loss, and prevent microorganisms from gaining entry to the body via the wound

8. Blood Groups Four different blood groups in humans: –A –B –AB –o Blood group are classifications of people based on the type of protein-carbohydrate complex biomolecule present on their red blood cells

9. Blood Groups There is another protein present on red blood cells in some populations of people and it is called the Rhesus factor (Rh) (The Rhesus factor [Rh] was first discovered in the Rhesus monkey by Landsteiner in 1940s) A person is either Rh+ or Rh– based on whether or not they have the Rhesus protein on the surface of their red blood cells