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Hemoglobin and Myoglobin in Medicine

Terms in this set (27)

Myglobin function
Stores O2 in the muscle
Hemoglobin function
Red blood cells, transports O2 from lungs to tissues
Myglobin structure
Monomer, 1 subunit, 1 domain, alpha helices and random coils
Percent of similarity between Hb and Mb, describe structural differences
38%
Extra loop in Mb compared to Hb alpha
Hemoglobin structure
Tetramer (2 alpha and 2 X subunits are different)
Non-alpha subunits in adults, fetuses, adult human minor form.
Beta
Gamma
Delta
Free heme binds __ very tightly.
CO
This is why we need protein around heme to hinder CO binding.
Oxygen ___ Fe __ to Fe __ in a heme group. This causes...
Oxidizes
II
III
Iron 3 can't carry oxygen anymore.
Change in color of heme can be detected by ___ or ___.
Eyes or spectrophotometry (shows how oxygenated heme is)
Hb oxygen binding is ___ and we know this because the linear graph has the following shape...
Cooperative
Sigmoidal at beginning, hyperbolic after that.
Myoglobin binding curve shape
Hyperbolic
Which binds more tightly? Hb or Mb
Mb
(Pulls oxygen off of hemoglobin)
Hb cooperativity comes from
Conformational change of Hb tetramer, caused by oxygen binding.
BPG (bisphosphoglycerate) is an ________ regulator of Hb. How many BPG's bind per Hb tetramer? What does binding site look like?
Allosteric
1 molecule binds per tetramer of Hb.
Lots of positively charged side chains in binding site (negative ligand)
BPG binds preferentially to ___ form of Hb. Increasing amount of BPG causes equilibrium shift...
De-oxy
Equilibrium shift toward deoxy form of Hb (helps deliver oxygen to tissues).
Without BPG, Hb binding curve resembles ___.
Myoglobin (hyperbolic)
BPG can be up regulated by ___ and down regulated by ___.
Hypoxia/altitude
Storage/shelf life
What is a difference between fetal Hb and adult Hb?
Serine side chain in BPG binding site, hydroxyl group which is polar but not enough to stabilize BPG binding.
Other 2 molecules that cause allostery in Hb
H+ (weakens O2 binding)
CO2 (lowers O2 affinity and reversible binding at N-terminal amines)
Hb and Mb moonlighting function
Change NO to NO3- which oxidizes Fe II to Fe III
Hb and BPG formations at lungs
O2 high concentration, Hb forces to high affinity state, BPG forced to dissociate
Hb and BPG formation at fingertips
O2 low, dissociates from hemoglobin, reverts to low-affinity state, BPG binds to facilitate low affinity state.
Methemoglobinemia and antidote
Fe III can't bind oxygen, can never reach high oxygen saturation. Antidote: methylene blue
How does one CO binding to Hb Impact all binding sites?
1 binding locks the rest of the sites in high-oxygen-affinity state (can't carry as much, can't release what we have in the tissues)
Thallesemia
Loss of 1 Hb subunit
Don't have proper ratio (stoichiometry). Extra units accumulate and block things, also can't bind oxygen very well.
Hemoglobinopathy
First one = sickle cell anemia
Mutation of amino acid side chain
Ex: Hb Kansas, Asn to Thr (key location for quaternary conformational change)
Problems identified with synthetic blood attempts
Free Hb cannot withstand the stress/pressures of circulation, free Hb scavenged NO in blood cells
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