Haemoglobin Flashcards
What is the primary function of RBCs?
Oxygen transport from lungs to cells
Carbon dioxide transport from cells to lungs
How are RBCs made?
A proerythroblast is converted into an erythroblast, the erythroblast then loses its nucleus and forms a reticulocyte. The reticulocyte then loses its mitochondria and ribosomes and becomes an erythrocyte.
How does the shape of RBCs help the function?
Biconcave shape (held together through cytoskeleton e.g. spectrin and actin)- a larger surface area for diffusion from the surface. Thin cell walls - short diffusion distance allowing for quicker exchange. Flexible so can squeeze through the capillaries.
How do RBCs get energy?
No mitochondria so no aerobic respiration, so all the ATP comes from glycolysis
Why do RBCs become fragile and rupture with age?
No ribosomes so no new protein synthesis, so the cytoskeletal proteins become fragile
What is haemoglobin and what is its structure?
Polypeptide that binds oxygen and transports it around the body.
Formed of 4 peptide chains, 2 alpha globulin chains and 2 beta globulin chains. Each of the 4 chains contains a haem group (that each contain and Fe atom) that will bind oxygen. So each haemoglobin molecule can carry 4 oxygens.
How is iron from the diet transferred to the blood?
absorbed from the intestine and binds to transferrin, then transported to the plasma.
How are old RBCs destroyed?
The spleen destroys them and converts haemoglobin into bilirubin, the liver metabolises bilirubin and excretes it in the bile (excreted in the faeces)
What 2 factors govern haemoglobins ability to bind oxygen?
The partial pressure of oxygen - the higher the partial pressure the higher the saturation.
The number of free oxygen binding sites available in the molecule. Needs free binding site. the first oxygen binding is the hardest the next make conformational changes and is easier to bind.
What is the Bohr Effect?
During anaerobic exercise there is a rise in lactic acid, this decreases the pH of the blood. The increase in protons can cause a conformational change in the Hb meaning it has a lower affinity for oxygen, so more oxygen can be released into active tissue.
What other molecules can bind to haemoglobin?
Carbon dioxide - causes a conformational shape change so O2 cannot bind - more is released
Protons - can denature the active site if too low so oxygen cannot bind - more oxygen is released.
Carbon monoxide - outcompetes oxygen (stronger bonds form)
Glucose - binds irreversibly to haemoglobin.
What are the 2 major classes of inherited RBC disorders?
Haemoglobinopathies = qualitative- mutation in global genes = abnormal globing chains e.g sickle cell anaemia
Thalassaemias - quantitative - globi chains are normal but lower amounts or absent due to defects at the level of gene expression
