Topic 7: Red blood cells and the haemoglobin Flashcards
What should be mentioned in this topic?
- Red blood cells - Hemoglobin - Age effect - Transport of Blood Gases - Hemoglobin as a buffer - Degradation of the hemoglobin - Factors affecting RBC Synthesis
Red Blood Cells:
- No mitochondria -Average lifetime: Horse, dog - 120 days Cattle, Swine – 60 Birds – 30
Red Blood Cells: Hemoglobin amount (Hb)
120-180g/L 35% haemoglobin concentration in 1g RBC.
RBC - data:
- Mean Corpuscular Hemoglobin Concentration (MCHC) - Mean Corpuscular Hemoglobin (MCH) - Mean Corpuscular Volume (MCV)
Hemolysis
Hemolysis is the leakage or disruption of blood cells. Osmotic hemolysis: - RBC in isotonic solution – Cell does not change - RBC in hypotonic solution – Water flows into cell, cell swells up - bursts - RBC in hypertonic solution – Water leaves cell and cell shrinks.
Red Blood Cells: Osmotic resistance
RBCs can adapt to slight changes easily. This is called osmotic resistance. The minimal resistance is 70-120mmol/L NaCl. The maximal resistance is 50-90mmol/L NaCl. Osmotic resistance is due to spectrin protein molecules on the internal side of the membrane giving it flexibility. These molecular springs are fixed forming a net on the internal side of the cell by ankyrine, actin and smaller connective molecules.
Haemoglobin
It is the pigment colouring the red blood cells and plays a main role in the transport of the blood gases and the forming of the blood’s buffer capacity. Synthesis requires Fe, Cu, Co, Mn, Zn, Pyridoxin B6 among others.
Haemoglobin: ferro-protoporphyrine
-The haem is a ferro-protoporphyrine. -In the porphyrine base, iron only has 4 coordination sites. - The two other valences involved are bound to the imidazole ring of the protein under and over the porphyrine base. - Only the iron atom can bind the Oxygen reversibly – Oxygenation (not oxidation). The oxygenated derivative is methaemoglobin. -This binds oxygen irreversibly and is produced under normal conditions too but it is reversed by the methaemoglobin-reductase – NADPH system.
Haemoglobin: Age effect.
Adult animal: Hb-A = 2 alpha + 2 beta chains Foetal period: Hb-F = 2 alpha + 2 gamma chains
Transport of gases: O2
-Binds to Fe2+ -1 hem binds 1 O2
Transport of gases: CO2
- Carbamino-haemoglobin - Responsible for about 20% of the complete CO2 blood-transport - Hb-NH2 + CO2 = Hb-N-COOH
Transport of gases: CO
- Binds reversibly though with 200 times larger affinity than to Oxygen
Transport of gases: OH and Cl radicals
- Binds irreversibly
Haemoglobin as Buffer
Hb- anion is one of the two most important buffer bases in the blood. Buffer action is ensured by: - HHb/Hb- - 35% of the buffer capacity of the blood is provided by haemoglobin. The deoxygenated Hb is a better proton acceptor than the oxygenated one
Factors affecting RBC Synthesis:
- Oxygen supply - Kidney status - Age