Lecture 16 & 17 Flashcards
myoglobin and hemoglobin
What is myoglobin and where is it found?
a monomeric protein that has O2 storage ability due to its high affinity for it. it is found in the tissues.
What is hemoglobin and where is it found?
a tetramer protein that has the ability to change affinity for O2 making it great for transporting from lung to tissue. found in the blood
what are the roles of hemoglobin?
-transport o2 from lungs so tissues
- transport some co2 from tissue to lungs
What is hemoglobin sensitive to whereas myoglobin is not?
pH, CO2 and BPG
Myoglobin bonding
permitting binds to O2 by its co-factor heme his 7 and 8 hold the iron
what is heme?
is it when the protoporhrin 9 (phorin ring) binds to iron allowing the protein to bind to O2
What is porphyria?
a genetic disease that causes lose of the cofactor heme. The symptoms include excessive hairiness and sensitivity to light.
What happens with myoglobin level when active
Myoglobin is will become 20% less saturated when muscle is active as mitochondria will be consuming the O2
Why is hemoglobins quaternary structure important?
it is needed for cooperative binding and allosteric regulation by CO2, pH and BPG
what are the 2 states of hemoglobin?
Relaxed (R) and Tense (T)
What is the R state?
It is when the hemoglobin has a high affinity to O2 because the structure pulls the 2 betas together be the F helix being planar
what is the T state?
When the hemoglobin has low affinity to O2 as the heme is puckered (trigonal state) and the betas are not close together
what are the shape of the oxygen binding curve of myoglobin and hemoglobin
Myoglobin- hyperbolic
hemoglobin - sigmoidal
What allosteric factors at the tissues cause hemoglobin to unbind o2
(ie. go into T state)
-BPG build up (intermediate of glycolysis
- lower pH
- high levels of CO2
What allosteric factor stabilizes the t state
BPG
Why are fetal O2 binding cures more to the left than the mothers
fetal blood has a lower affinity for BPG because it must have a higher affinity for O2 because the blood that comes to the baby is already low in O2
what’s the difference between maternal globin gene and fetal globin gene
instead of 2 beta and 2 alpha chain, fetal gene has 2 alpha and 2 sigma chains. (72% similar to adult gene except no His143, which is responsible for BPG binding, instead having serine)
How does low pH affect hemoglobin?
it protonates His146 which stabilizes the T state, pushing the curve to the right
How does CO2 affect hemoglobin?
1) high levels of CO2 pushes the bicarbonate equation to the right and more H+ is produced which binds to haemoglobin and stabilizes the T state
2) the binding is called carbamate and it creates salt bridges that further promote the stabilizing of the T state
how does blood cells become sickled?
glu6 changes into val 6
what happens when blood is sickled
can’t carry properly carry o2 and the capillaries are prone to clotting duets irregular shape
