Pulmonary Biochemistry Flashcards
Myoglobin, Hemoglobin, and Hemoglobin variants
What does myoglobin resemble?
The B-chain of hemoglobin
Do myoglobin and hemoglobin have the same AA sequence?
No, even though the structures are very similar
Where is myoglobin found? Why?
Found in muscles to hold oxygen there
Where are forces the strongest between units of hemoglobin?
Forces between a1 and B1, as a pair, and a2 and B2 as a pair - held together by 30 residues each
What two helices usually make up the pocket where heme is found?
E and F
What does the alpha unit of hemoglobin lack that the B has?
short D helix (everything else A-H is identical)
What state must iorn be in to bind oxygen?
Fe2+
What histidine does iron interact with?
Proximal histidine
When is iorn pulled into the plane of the heme ring? What subsequently also moves?
When oxygen binds
Proximal histidine and polypeptide chain also move
What reduces iorn from 3+ to 2+? What reduces the reducer?
Cytochrome b5 reductase reduces iron
NADH reduces cytochrome b5
What is the normal percentage of methemoglobinemia in the blood? What is a clinical feature of people with congenital deficiency of cytochrome b5 reductase?
3%
Cyanotic
What treat can be used to reduce iron from 3+ to 2+?
Methylene blue
What disrupts the salt bridge between His 146 and Asp 94? Does this result in the tense or relaxed state?
When oxygen binds to iron
Relaxed state
What is the purpose of the distal histidine? Without it, what is the result?
To stabalize oxygen so it doesn’t leave as a superoxide ion
Methemoglobin is the result
How does the P50 of hemoglobin related to the P50 of myoglobin? What does this ultimately allow for?
Hemoglobin P50 is 10x higher
Allows for myoglobin to hold onto O2 dissociated from hemoglobin
