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
most common cause of microcytic anemia
iron deficiency and thalassemia
microcytic anemia symptoms
pale skin, weakness, irritability, shortness of breath, rapid HR, pica
valine vs glutamate (sickle cell)
valine is non-polar and hydrophobic, causing increased hydrophobicity in hemoglobin