Lecture 3 Flashcards
where is myoglobin found?
muscle
what is the function of myoglobin?
provide reserved supply of O2 and facilitates rapid diffusion of O2 within the muscle
how many polypeptide chains does myoglobin contain?
one
what is the function of hemoglobin?
O2 carrier in blood
how many polypeptide chains does hemoglobin contain?
four
what kind of polypeptide chains does hemoglobin contain?
two identical alpha chains and two identical B globin chains
do hemoglobin and myoglobin have the same heme group?
yes
what are the functional differences between myoglobin and hemoglobin?
Hemoglobin is more complex than myoglobin
-Hb transports H+ and CO2 in addition to O2
- binding of O2 is regulated by H+, CO2 and 2,3BPG
how many molecules of O2 can myoglobin bind?
1
how many molecules of O2 can hemoglobin bind?
4
Is hemoglobin a allosteric protein?
yes
is myoglobin a allosteric protein?
no
allosteric protein
protein that changes from one conformation to another when it binds to another molecule or covalently modified
- alters the functional activity of protein
positive cooperativity
binding of O2 to hemoglobin enhances binding of more O2 to the same hemoglobin
what affects the affinity of hemoglobin to O2?
pH and binding of CO2
- also regulated by 2,3BPG
which has a higher affinity for oxygen, hemoglobin or myoglobin?
myoglobin, because hemoglobin is regulated by 2,3BPG
what are the differences between myoglobin and hemoglobin dissociation curve?
myoglobin is hyperbolic vs hemoglobin is sigmoidal
what is the significance of the O2 binding curve of hemoglobin?
hemoglobin is fully saturated with O2 in the lungs (100 torrs) but relreases more than half of its bound O2 in capillaries of active muscles and issues where pO2 is 20torrs
what is the significance of cooperatively binding of O2 to hemoglobin?
- communication among the heme groups of Hb
- allows Hb to deliver twice as much as O2 to tissues than if they were to act independantly
when are beta chains of hemoglobin closer to one another?
when hemoglobin is in oxygenated form, causing strain on other subunit, causing noncovalent bonds to break
what causes changes in hemoglobin quaternary structure?
the movement of Fe atom in heme
- Fe moves into plane (Fe is out of plane when deoxygenated due to steric repulsion)
what factors regulate Hb quaternary structure and O2 affinity?
pH, CO2, biding of 2,3 BPG
does a low pH or high pH enhance the release of O2 by hemoglobin?
low pH (acidity), shifts dissociation curve to the right, decreasing O2 affinity
does pH affect myoglobin affinity of O2?
no
what promotes the release of O2 from Hb?
CO2, increasing CO2 lowers affinity of Hb for O2
what kind of proteins are used for protein studies?
- utilize crude (not pure) protein preparations
- utilize purified or highly enriched preparations
