B4.024 - Myoglobin and Hemoglobin Flashcards
biological role of Mb
stores O2 in muscle
biological role of Hb
red blood cells, transports O2 from lungs to tissues
what is the % of similarity between Hb and Mg
38%
quaternary structure of Hb and Mg
Hb - tetramer (alpha 2, X2) Mg - monomer
what form of Hb can assemble but doesnt function
B4
free heme binds what more tightly than O2
CO
what hinders CO binding
protein
what role does protein have in heme prosthetic groups
hinders CO binding Inhibits oxidation of iron
describe the color change of hemoglobin
when bound to oxygen it has a red color when not bound to oxygen it has a blue color
describe the curve of oxygen binding to Hb
its sigmoidal because of cooperative binding
how many binding events does Hb have
4 - 4 binding sites
what does a Mg binding curve look like
simple hyperbolic
which binds more tightly to oxygen Hb or Mg and why
Mg because you need to steal it away to give to muscle
what causes cooperative binding
conformational change with oxygen binding offers higher affinity
where does BPG come from
synthesized in erythrocytes from glucose
what does BPG do with Hb
can bind to Hb (has many binding sites)
describe BPG charge
its very negatively charged allowing it to bind to positively charged AAs
what does BPG do with Hb
binds to low affinity form drives reaction back to deoxy form of Hb
what would the Hb binding curve look like without BPG
the Mg curve
when is BPG upregulated and lost
up-regulated with hypoxia lost during blood storage (contributes to shelf life) because its used up for energy
how is BPG binding different in fetal Hb
not as high of an affinity for binding, because of higher need for taking oxygen from moms blood
what does H+ do with Hb
weakens oxygen binding
what does CO2 do with Hb
allosteric inhibitor of O2 affinity
describe binding of CO2
covalent and reversible binding at N terminal amines
what do Mb and Hb moonlight as
enzymes changing NO to NO3 this disables heme so it cant bind oxygen
describe the color change in blood due to NO3 binding to heme and blocking oxygen binding
it turns chocolate brown
how does altitude affect Hb binding
higher altitude has less oxygen concentration oxygen in body will diffuse back out
what does the presence of Fe3+ mean for the Hb binding curve
never can get fraction binding all the way to one so the curve is lower
antidote to drugs that oxidize Fe2+?
methylene blue
describe symptoms of CO poisoning at <10% >10%, 20%, 25%, 30% COHb level
<10% - headache dizziness >10% - slight headache 20% - slight headache, loss of judgment 25% - frontal headache 30% - dizziness, nausea, convulsions
why is CO poisoning so toxic
binds any protein with heme binds at extremely low [CO] substoichiometric conditions it still has effect
what does it mean that CO has effects at substoichiometric conditions
only one bound CO causes an effect, dont need 4
what does CO do to heme
precules O2 binding to this site enhances O2 binding at other sites
what does the CO Hb binding curve look like
like Mb but lower bc it cant bind as much O2 but cant release what it has
what is thalassemia
loss of one subunit stoichiometry gets messed up can aggregate and precipitate causes anemia
what are hemoglobinopathies
sickle cell point mutation affecting Hb
what does Hb scavenge
NO, causes spike in BP
if any NO makes it too far what happens
Mg sequesters it to block it from messing with ETC
what mops up NO
Free Hb
what are things people are trying to make synthesized Hb
Covalently cross link tetramer copy Hb of ocean mammals increase size to avoid NO zone
what type of secondary structure is this and how many domains
alpha helix, random coil
1 domain
why AAs would you expect on the interior of this and on the surface
hydrophobic - interior
hydrophilic - exterior
A. Green positions
B. Yellow positions
C. white positions
D. positions with a dash
C - white positions
what happens to Hb curve as pH decreases?
The O2 affinity higher or lower?
Midpoint of new curve higher or lower for pO2?
How does this make sense?
what happens to the Hb cureve with Hb Kansas?
