Topic 7: Red blood cells and the haemoglobin

Question 1

What should be mentioned in this topic?

Answer 1

• Red blood cells - Hemoglobin - Age effect - Transport of Blood Gases - Hemoglobin as a buffer - Degradation of the hemoglobin - Factors affecting RBC Synthesis

Question 2

Red Blood Cells:

Answer 2

• No mitochondria -Average lifetime: Horse, dog - 120 days Cattle, Swine – 60 Birds – 30

Question 3

Red Blood Cells: Hemoglobin amount (Hb)

Answer 3

120-180g/L 35% haemoglobin concentration in 1g RBC.

Question 4

RBC - data:

Answer 4

• Mean Corpuscular Hemoglobin Concentration (MCHC) - Mean Corpuscular Hemoglobin (MCH) - Mean Corpuscular Volume (MCV)

Question 5

Hemolysis

Answer 5

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.

Question 6

Red Blood Cells: Osmotic resistance

Answer 6

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.

Question 7

Haemoglobin

Answer 7

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.

Question 8

Haemoglobin: ferro-protoporphyrine

Answer 8

-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.

Question 9

Haemoglobin: Age effect.

Answer 9

Adult animal: Hb-A = 2 alpha + 2 beta chains Foetal period: Hb-F = 2 alpha + 2 gamma chains

Question 10

Transport of gases: O2

Answer 10

-Binds to Fe2+ -1 hem binds 1 O2

Question 11

Transport of gases: CO2

Answer 11

• Carbamino-haemoglobin - Responsible for about 20% of the complete CO2 blood-transport - Hb-NH2 + CO2 = Hb-N-COOH

Question 12

Transport of gases: CO

Answer 12

• Binds reversibly though with 200 times larger affinity than to Oxygen

Question 13

Transport of gases: OH and Cl radicals

Answer 13

• Binds irreversibly

Question 14

Haemoglobin as Buffer

Answer 14

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

Question 15

Factors affecting RBC Synthesis:

Answer 15

• Oxygen supply - Kidney status - Age

Question 16

Membrane hemolysis:

Answer 16

Physical effects: -Freezing, Dissolving, Shaking, Shocking Chemical effects: -Acids, Liposolvents, -Surface tension reducers Toxin Effect: -Bacterial, Snake, Plant

Question 17

Globin

Answer 17

The sterical structure of globin mainly determines the characteristics of the oxygen binding. This structure allows allosteric stimulation, and it is able to bind a new oxygen even stronger after accepting the former one.

Question 18

Degradation of the hemoglobin:

Answer 18

During the degradation of the hemoglobin phagocytes convert the HEM part to bilirubin. Albumin binds Bilirubin in the circulation. This is called bilirubin-I or indirect bilirubin or non-conjugated bilirubin.