Heme Metabolism - w5 Flashcards
What is the structure of porphyrins?
cyclic compounds that bind metal ions
What is the structure of heme?
tetrapyrrole ring of protoporphyrin IX with central Fe2+
What links the pyrrole rings of heme together?
methenyl bridges (-HC=)
How many groups of compounds are there in a heme tetrapyrrole ring?
4 methyl groups
2 vinyl groups
2 propionate groups
What are the two places where heme is synthesized?
85% in bone marrow erythroid precursors / 15% liver
What is the enzyme that detoxifies oxidative stress in the body?
catalase
What do cytochromes do?
detoxify
What is the important AA and coenzyme that begins heme synthesis?
glycine and succinyl co-A
Where does the finished product heme (with Fe2+) get assembled?
mitochondria
What is the enzyme that has the highest catalytic power?
uroporphyrinogen decarboxylase
What is clinical ion name for Fe2+?
ferrous ion
What is the rare defect in heme synthesis?
porphyrias
What causes porphyrias?
accumulation and increased excretion of porphyrins or porphyrin precursores (not accu of heme)
How does porphyria affect the skin?
increases skin photosensitivity (oxidative damage)
What is the most common porphyria (hepatic)?
porphyria cutanea tarda
What are the physical symptoms of porphyria cutanea tarda?
skin eruptions and red coloured urine
Which porphyria is congenital?
erythropoietic
What degrades RBCs?
phagocytes in the liver and splkeen
What enzyme begins heme degradation by releasing Fe2+?
heme oxygenase
Which compound in heme degradation is green?
biliverdin
How does bilirubin get transported to liver?
first binds to albumin to make a complex
In liver, what does bilirubin conjugate with?
glucaronic acid
Where does conjugated bilirubin go to?
bile
Which stage of bilirubin becomes feces?
stercobilin
