RBCs And Haemoglobin (haematology, Physiology) Flashcards
What is the main function of RBCs
They carry oxygen from the lungs to systemic tissue and carbon dioxide to the lungs.
Explain how RBCs transport carbon dioxide to lungs (8)
•Co2 diffuses from the peripheral tissues into the systemic capillaries.
•Only 7% of CO2 remains in plasma.
•About 25% of the CO2 binds to haemoglobin to form carbaminohaemoglobin.
•70% of the CO2 react with water to form CA which dissociate to form bicarbonate and hydrogen ions, the hydrogen ions are buffered by haemoglobin.
•The bicarbonate moves out of the RBCs in exchange for Chloride ions.
•In the lungs, dissolved CO2 diffuses out of the plasma into the alveoli.
•By the law of mass action, CO2 unbinds from haemoglobin and moves out of the RBCs.
•The CA reaction reverses, pulls bicarbonate into the RBCs and convert it back to CO2.
Which enzyme catalyses the reaction btwn water and CO2?
Carbonic anhydrase enzyme
Why do RBCs lack mitochondria?
Because RBCs carry oxygen, and cellular respiration in the mitochondria utilises oxygen. So if there is mitochondria in the RBCs the process will utilise the oxygen and decrease the oxygen supplied to tissues.
By which process do RBCs generate ATP?
Glycolysis
What are the normal haematocrit values?
Males- 46%
Females- 42%
What happens when an erythrocyte is placed in:
1. A hypertonic medium
2. A hypotonic medium
- It shrinks, but the rigid cytoskeleton remains and form a spiky surface, we now refer to it as a crenatus.
- It swells and lose its biconcave disc shape.
In which case does the RBC change its shape?
In a sickle cell disease
During the metabolism of RBCs which molecule is produced by the reactions associated with glycolysis?
2,3-bisphosphoglycerate
What do we call the protein found in RBCs?
Haemoglobin
Normal values for haemoglobin levels
Males: 14-18 g/dL
Females: 12-16 g/dL
What forms when haemoglobin binds to:
1. Carbon dioxide
2. Oxygen
3. Carbon monoxide
- Carbaminohaemoglobin
- Oxyhaemoglobin
- Carboxyhaemoglobin
What do we call the molecule that forms when haemoglobin has Fe3+?
Methemoglobin
Explain the process of formation and metabolism of hemaglobin (6)
-Fe is ingested in diet.
-Fe is absorbed in the small intestines by active transport.
-Fe is transported by transferrin to the bone marrow where is binds to globin and forms haemoglobin.
-Haemoglobin in RBCs in metabolised in the spleen and it forms bilirubin.
-Bilirubin and other metabolites can be excreted in kidney through urine or in large intestines through faeces.
-Liver metabolises bilirubin and excretes it in the bile.
-Excess iron is stored in the liver as ferritin.
Three stages of erythropoiesis in foetal life
Mesoblastic stage
Hepatic stage
Myeloid stage