2401- Biochemistry I, II, III Flashcards
Give the characteristics of myoglobin.
1 subgroup and 1 heme group
Proximal residue to heme- His F8 or His93
Has one binding site for O2
Made of of 8 helices, E, and G
Found in sketetal and cardiac muscle
Functions well for O2 storage
One heme group attached to its globin structure.
What is the state of iron in deoxymyoglobin?
Ferrous (Fe2+)
At which site does O2 bind to in the hemoglobin structure, “The Globin Fold”?
Distal histidine, E7
It establishes a hydrogen bond with O2 and plays an important physiological role in discriminating between ligands.
As it relates to the binding curves of myoglobin and hemoglobin, what is the significance of both curves?
Myoglobin has a high affinity for O2, therefore, at low PO2, its affinity would be greater to hemoglobin
Hemoglobin has a lower affinity to O2, thus as low levels the affinity would be less than to myoglobin.
At high PO2, both hemoglobin and my goblin would have similar affinities.
In the myoglobin molecule, what is the heme group bound in? And what is the residue?
E, F and G helices hydrophobic pocket
- His F8 (His93)
State the reason why deoxymyoglobin is unable to fit in the porphyrin plane (ring) whiles oxymyoglobin is able to fit in the plane.
Deoxymyoglobin has a higher spin (5 coordinate structure) Fe2+ therefore, it will sit above the plane.
Oxymyoglobin is a low spin (6 coordinate structure) with Fe2+ and Fe3+, the iron moves into the plane.
What stops the oxidation of Fe2+ to Fe3+ in a heme-containing protein?
The sequestering of each heme within the protein structure.
This restricts access to the two open coordination bonds.
Which structure binds at the following sites of hemoglobin:
A) proximal
B) distal
A) Nitrogren atom and residue of heme, histane F8 or His93
B) O2, Histane E7 which is formed by a H2 bond.
In which part of the body is does hemoglobin have a high affinity for O2?
Lungs.
Myoglobin has a greater affinity of O2 where?
Tissues where PO2 is low.
Give the characteristics of hemoglobin.
4 subgroups, 4 heme groups
A2b2
Multiple O2 binding sites
Functions better for O2 transport
What molecule stabilizes the following states of hemoglobin:
A) R state
B) T state
A) O2 stabilizes the R state of hemoglobin
B) 2,3- BPG, H+, CO2 stabilize the T state
A) when o2 is absent the T state is stabilize forming deoxymyoglobin
B) If the following is absent the R state is stabilized.
Describe allosteric proteins.
It is one where the binding of a ligand to one site affects another binding site on the same protein.
O2 is an example. Acts as a ligand and a homotropic modulator
Describe the Bohr Effect.
Is the effect of pH and CO2 on the release of oxygen by hemoglobin.
In the lungs, an increase in pH and low CO2 levels leads to an increase in the affinity of O2. Hemoglobin binds to O2 and releases H+
In the tissues, a decrease in pH (increase in H+) and high CO2 levels leads to a decrease in the affinity of O2. H+ is bound and O2 is released.
Explain how CO2 and O2 can effect the binding of each on hemoglobin.
When a higher level of CO2 is present in the tissues, hemoglobin binds to CO2 and the affinity for O2 decreases. When O2 becomes a greater concentration, hemoglobin binds to O2 and the affinity for CO2 decreases.
