Hemoglobin Flashcards
final enzyme of electron transport
cytochrome oxidase - O2 is reduced to H2O
facilitates O2 diffusion to the mitochondrion
Mb
function of Mb
intracellular transport and temporary storage of O2 needed for aerobic metabolism of muscle
secondary structure of Mb
8 a-helices
quaternary structure of Hb
a2B2
- 2 x a:B dimers
- quilibrium favors tetramer
ApoHb vs HoloHb
protein without vs with prosthetic group
-HoloHb = 1 heme/subunit = 4 hemes
how many hemes/O2 binding sites in Hb
4 (1/subunit)
basis for Hb’s cooperative binding, resulting in a sigmoid binding curve
T vs R
-R = more O2 bound = higher O2 affinity until Hb molecule is sat’d
porphyrin
- tetrapyrrole
- forms protoporphyrin IX, which chelates Fe
metal chelating site on Hb
- binds Fe
- 4 nitrogens of 4 pyrrole groups point inward
substituent groups on heme prosthetic group (a pyrrole)
4 methyl, 2 vinyl, 2 propionate
state of Fe in deoxyHb
ferrous = Fe(II)
-reduced
(high/low) O2 affinity at P50
high
Mb vs Hb curve
hyperbolic vs sigmoidal
Mb ___ O2 in conditions under which Hb ____ it
binds
releases
Which has higher P50 (Mb/Hb)
Hb
O2 binding negative effectors
decrease affinity of O2 for Hb allows unloading in tissues, while loading can occur in lungs
-BPG, CO2, H+
O2 binding positive effectors
increase affinity of O2 for Hb - bad, can’t unload
BPG
stabilizes T state, lowers affinity of Hb for O2
BPG binds to and stabilizes ______, and ______ Hb’s affinity for O2
T quarternary state of Hb
decreases
Hb’s affinity for O2 is fine-tuned by altering this concentration in the blood
BPG
shift Hb curve right
unload
ex. BPG
short term acclimation to low O2 pressure
shift Hb curve right with BPG; deliver same amt of O2 as at sea level without reducing tissue O2 pressure
does pH modulate Mb’s affinity for O2?
no
pH in lungs which allows for higher Hb-O2 affinity
high pH, low [H+]
pH in tissues which allows for lower Hb-O2 affinity
low pH, high [H+]
carbamylation of Hb
- CO2 combines reversibly with N on protein
- favors T state - reduced Hb-O2 affinity
effect of CO2 and H+ on HB-O2 affinity
capillaries: CO2 stabilizes T state, O2 is released
- H+ further reduces affinity
why does fetal Hb bind O2 with higher affinity
fetal Hb has lower affinity for BPG
HbS
- a2B2
- sickle cell anemia
HbH
- B4
- a-thalassemia
HbBarts
gamma4
-a-thalassemia
methemoglobin
ferric - doesn’t bind O2
sign of methemoglobinemia
cyanosis
