Biochem 2 USMLE Flashcards
underproduction of heme causes this type of anemia
microcytic hypochromic
accumulations of heme intermediates causes thius
porphyrias
this type of porphyria inhibits ferrochelatase and ALA dehydrase. Cooproporphyrin and ALA accumulate in the urine
lead poisoning
this type of porphyria results from a deficiency in uroporphyrinogen I synthetase. Porphobilogen and delta-ALA accumulate in urine
Acute intermittent porphyria
this type of porphyria results from a deficiency in uropophyrinogen decarboxylase. Uroporphyrin accumulates in urine (tea-colored). results in photosensitivity
Porphyria cutanea tardia
symptoms of porphyrias (5 Ps)
Painful abdomen Pink urine Polyneuropathy Psychological disturbances Precipitated by drugs
heme is scavenged from RBCs and ____ is reused
Fe++
heme ->_____->bilirubin
biliverdin
bilirubin is toxic to this organ system
CNS
bili is transported by this protein
albumin
bili is removed from the blood by this organ
liver
bili is conjugated with this ____
glucuronate
bili is excreted in this supstance
bile
where in the body is bili processed into its excreted form
intestine
some ________, an intestinal intermediate, is reabsorbed into blood and excreted as urobilin into urin
urobilinogen
this poison has a 200x greater affinity than O2 for HGB
CO
hemoglobin is composed of 4 polypeptide subunits. describe them
2 alpha
2 beta
HGB exists in 2 forms what are they
T (taut) low affinity for O2
R (relaxed) high affinity for O2 (300x)
Hgb exibits _______ cooperativity and ________ allostery (accounts for the sigmoid-shaped O2 dissociation curve for hgb), unlike myoglobin
positive
negative
name the things that favor the relaxed form of hgb (shifting dissociation curve to the right, leading to O2 unloading)
increased Cl-,H+,CO2,2,3BPG, hight temp.
mneu: when you’re relaxed, you do your job better (carry O2)
what are the fetal hgb subunits
2alpha
2gamma
fetal hgb has a lower affinity for _____ than adult hgb and thus has a higher affinity for O2
2,3-BPG
Iron in hgb is in a _____ state (ferrous, Fe++)
reduced
this is an oxidized form of hgb (ferric, Fe++) that does not bind O2 as readily but has increased affinity for CN-.
methemoglobin