catabolism of haem Flashcards
haemoglobin definition
an iron containing oxygen-transport metalloprotein in red blood cells
haem definition
non-protein prosthetic group found in haemoglobin
a coordination complex consisting of an iron ion coordinated to a porphyrin
where does degradation begin + explained?
senescent erythrocytes are removed from circulation in the spleen
explain degradation of haem
- haem reduced to biliverdin by heme oxygenase using NADPH
- iron is reduced from the molecule and CO
- biliverdin is converted to bilirubin by biliverdin reductase
explain transport of bilirubin
bilirubin is transported into the liver by facilitated diffusion, bound to albumin
how is bilirubin made water soluble?
conjugated with glucuronic acid to become more water soluble
catalysed by UDP-glucuronosyltransferase
excretion of bilirubin explained
excreted from the liver in bile
intestinal bacteria deconjugate bilirubin so it can be absorbed by intestinal cells and transported to kidneys with urine
the remainder travels down digestive tract and is converted to stercobilinogen, oxidised to stercobilin and excreted- forming brown colour of faeces
what signifies hyperbilirubinaemia?
jaundice- yellowing colour
what does indirect bilirubin show in a blood test?
the amount of unconjugated bilirubin created from red blood cell breakdown
what does direct bilirubin show?
conjugated bilirubin, which means it has been processed by the liver
what would results mean?
high indirect bilirubin- body breaking down too many RBCs, haemolytic anamia
low indirect bilirubin- fine
high direct bilirubin - liver isn’t clearing bilirubin properly - going to the blood instead of bile
low direct - fine
common causes for elevated conjugated bilirubin
liver not working properly = hepatitis, Gilbert’s, cirrhosis, biliary stricture, cancer
common causes for elevated unconjugated bilirubin
hemolytic anemia- too many blood cells being destroyed from an autoimmune disease
transfusion reaction
