Protein V Flashcards
ferrohemoglobin
Fe+2, binds O2
ferrihemoglobin
Fe+3, does not bind O2
Fe+2
has proximal histidine on one side and binds O2 on other side
proximal histidine
binds the iron in heme
distal histidine
prevents heme groups from coming too close together –> prevents oxidation of iron; also reduces affinity of CO for heme
pO2 in capillaries
about 20 torr
when oxygen binds Fe _
it pulls it into the porphyrin plane, pulling proximal histidine into plane as well, causing it to reposition –> conformational change = quaternary structure
tense (T) state
deoxygenated heme
relaxed (R) state
oxygenated heme
sequential model
each heme independently converts from R to T
the higher the pO2 _
the more oxygen present in blood
stabilization of T state
releases O2
stabilization of R atate
binds O2 (high affinity)
muscles actively working
when active, muscles release CO2 and H+ –> this stabilizes the T state, causing the unloading of oxygen for the muscles
Bohr effect in lungs
high O2 promotes release of CO2 and H+
pO2 curve when more H+ (same for CO2)
protons stabilize the T state –> shifts pO2 curve to the right (causes higher pO2 because oxygen is released into blood)
formation of carbamates
stabilize T state
pKa in deoxyhemoglobin
pKa raised in histidine and terminal NH2 groups
2,3-BPG
2,3-BPG will only bind the T state –> no 2,3-BPG means R state –> so 2,3-BPG stabilizes T state; also it is synthesized during glycolysis
hypoxia
induces production of 2,3-BPG (allows shift from R to T to unload more oxygen)
2,3-BPG in RBCs
bonds hemoglobin and lowers its affinity for O2
Haldane effect
deoxygenation of the blood leads to an increase in its ability to carry CO2
fetal hemoglobin
alpha2gamma2; binds O2 with higher affinity because it binds BPG less tightly
microcytic anemia
tissues and organs do not get enough oxygen due to either decreased RBCs or lack of hemoglobin
