Blood Biochemistry 2
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What is the early form of a RBC called?
What is a major peripheral protein in the plasma membrane of RBCs?
What is the function of spectrin?
Spectrin interacts with other cytosolic peripheral proteins (ankyrin, actin, protein 1.4) to give mechanical stability and resilience to the RBC membrane. This means RBCs can withstand shearing forces and pressure changes while in circulation.
What are the four important types of integral RBC membrane proteins?
- Glycophorin A
- Glut 1
- Na+/K+ ATPase
- Anion channel (anion exchanger)
What is the function of glycophorin A?
Prevents RBCs sticking to other cells and vessel walls (thereby blocking blood vessels)
What does the glycosylation of RBC membranes give rise to?
What is the name of the condition where a developing foetus has a different blood group from its mother?
What is the function of glut 1?
It is a glucose transporter - it transports glucose into RBCs for glycolysis and PPP
What is the function of the anion channel?
It regulates the exchange of HCO3- and Cl-. When CO2 is dissolved into RBCs it reacts with water to form carbonic acid. Carbonic acid is quite unstable so it dissociates into HCO3- and H+. The H+ ion attached to Hb. The HCO3- ion would increase the pH of the cell if it was not removed so it is pumped out of the cell and the Cl- ion is pumped in to maintain the correct pH. This reaction occurs at the tissues in the body - the opposite reaction occurs at the lungs.
Is metabolism in RBCs aerobic or anaerobic?
Anaerobic - they have no mitochondria
What are Reactive Oxygen Species (ROS)?
ROS are formed when O2 becomes reduced. Examples include O2-, HOO, H2O2. ROS are quite toxic molecules that are beneficially used during phagocytosis and killing of bacteria but can cause cell damage by oxidising lipids and proteins in cell membranes.
What change occurs in the form of iron when it becomes oxidised?
Why is oxidation of iron bad?
Iron will only transport oxygen when it is in the Fe2+ form
What are the three main important pathways in anti-oxidant defences in RBCs?
- Glutathione (reducing agent which need NADPH)
- NADH/cytochrome b5 metheamoglobin reductase
- Superoxide dimutase and catalase enzymes
What is the major role of NADPH in RBCs?
To maintain glutathione in a reduced state.
What does glutathione (GSH) do in RBCs?
GSH non-enzymatically reverses oxidation of proteins. GSH itself becomes oxidised during this process to GSSG. It must be regenerated to prevent protein denaturation which requires NADPH and glutathione reductase
What is methaemoglobinaemia?
When there is abnormal amount of methaemoglobin formation
What are some of the clinical signs of methaemoglobinaemia?
- Cyanosis (purple coloured tongue / mucus membranes)
- Exercise intolerance
- Chocolate brown blood
- Anaemia (occasionally)
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