Hemoglobin Flashcards
Hemoglobin
Tetramer of polypetides (globins) which each contain a heme group
In adults, what type of globin chains are the tetramers comprised of?
2 alpha and 2 beta
Which amino acid is responsible for holding the heme group in place and is on the inside of the globin?
Histidine
Myoglobin
Oxygen storing molecule found in skeletal and cardiac muscle
A monomer
Which globin is more suited for storage and which is more suited for delivery?
Myo - storage
Hemo - delivery
p50
The partial pressure at which Hb is 50% saturated
What does the binding affinity curve look like for hemeoglobin?
Sigmoidal
What does the binding affinity curve for myoglobin look like?
Hyperbolic
Because of it’s monomer nature and binding affinity what must occur for myoglobin to give up its oxygen?
The environment must be heavily lacking in oxygen
Because of it’s quaternary structure, Hb participates in;
Cooperative binding
Where does Mb release its oxygen to?
Cytochrome oxidase to be used in the electron transport chain to fuel muscle contraction
In deoxyHb Fe is out of place with the heme. How does it go back into the correct plane?
Binding of oxygen sources
What are the two states each component of the Hb tetramer can exist in?
Tense or relaxed
How can an Hb tetramer component be in different states?
Due to salt bridges
It take more energy to bind to the first Hb because the salt bridges must be broken
Embryonic globins have what type of globin subunits?
Epsilon and zeta
Fetal globin has what type of globin structure?
Gamma
When is gamma globin completely replaced?
At birth
Which has a higher affinity for O2, fetal or adult Hb and why?
Fetal so that it can obtain as much oxygen from the mother’s blood without too much competition
What lowers the the O2 affinity of Hb?
2,3-BPG
by associating in the pocket formed by the Hb tet
What does 2,3-BPG do to lower O2 affinity?
Stabilizes the T-structure of Hb
Forms salt bridges
Low pO2 triggers more 2,3-BPG to be formed in Rapoport-Luberin shunt
What is the problem with banked blood?
2,3-BPG levels tend to fall decreasing the ability to release oxygen into tissues
Which is more soluble in blood? O2 or CO2?
CO2
How does CO2 become H2CO3?
When it diffuses into RBCs it become hydrated by carbonic anhydrase
Haldane effect
Describes how an inc in Hb-O2 binding dec the amount of proton binding
Bohr effect
How Hb binding to O2 is effected by pH
As CO2 levels rise, deoxyHb will bind to proteins much more readily than it will bind to O2
If the p50 exists in a high pH what occurs?
Hb is more prone to give up its oxygen in venous blood
What is the chloride/bicarb exchanger which moves HCO3-?
Band 3
For every HCO3- moved out of the cell, what moves into the cell and what is it called?
Cl-, chloride shift
Thalassemias
Describe when the ratio of alpha to beta globin subunits is not 1:1
Sickle cell
Describes a specific globin allele (Hbs) which results from a single nucleotide substitution and leads to the formation of fiberous polymers of Hb
Alpha-Thalassemia
A group of genetic disorders leading to altered levels of the alpha globin subunit
Beta-Thalassemia
Extremely heterogeneous group of genetic disorders resulting in changes in amount of beta-globin synthesis
Pts with higher HbF tend to do better
Sickle cell
Caused by single nucleotide substitution of beta-globin gene resulting in Glu-Val sub
Val causes a sticky patch
