Chapter 30: Blood Leaving Certificate Biology Higher Level
Composition of Blood • Blood has four main components: – Plasma – Red blood cell (erythrocytes) – White blood cells (leucocytes) – Platelets (thrombocytes)
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
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
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
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
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
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
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 1940 s) • 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
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