18 Questions
What is the primary function of oxygen transport systems in large animals?
To facilitate the pickup and release of oxygen at different locations
What is the key prosthetic group that allows globin proteins to bind oxygen?
The porphyrin ring with a central metal atom
How does the iron atom in the heme group interact with oxygen?
The iron atom temporarily accepts an electron from oxygen, forming a superoxide radical
What is the role of the proximal and distal histidine residues in the heme pocket?
The proximal histidine binds the iron atom, while the distal histidine stabilizes the oxygen binding
What is the significance of the Bohr effect in the regulation of hemoglobin?
It decreases the affinity of hemoglobin for oxygen at low pH
How does fetal hemoglobin differ from adult hemoglobin in its oxygen-binding properties?
Fetal hemoglobin has a higher affinity for oxygen, allowing it to obtain oxygen from the mother's bloodstream
What is the role of distal histidine in hemoglobin?
It inhibits methemoglobin formation.
How does hemoglobin enhance selectivity for oxygen?
By preventing the release of toxic superoxide.
How do myoglobin (Mb) and hemoglobin (Hb) differ?
Hb is a monomer, while Mb is a tetramer.
What effect does oxygen binding have on the magnetic properties of iron in hemoglobin?
The iron becomes paramagnetic upon O2 binding.
What happens to the Fe ion when oxygen binds to hemoglobin?
Fe ion increases its oxidation state.
In a simple binding reaction, what determines the equilibrium between P + L and PL?
[P], [L], rate constants, and temperature.
What structural change occurs in hemoglobin when oxygen binds?
The alpha helix shifts slightly, altering the alpha-beta interface
Why is the affinity of hemoglobin for oxygen lower in red blood cells compared to in vitro conditions?
The presence of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells
What is the primary function of 2,3-bisphosphoglycerate (2,3-BPG) in regulating hemoglobin activity?
It stabilizes the T (tense) state of hemoglobin, decreasing oxygen affinity
How does fetal hemoglobin differ from adult hemoglobin?
It consists of alpha and gamma globin chains instead of alpha and beta
What is the significant change in fetal hemoglobin that affects its interaction with 2,3-BPG?
The histidine at position 143 is replaced by serine
What is the Bohr effect in relation to hemoglobin?
The decrease in hemoglobin's affinity for oxygen at lower pH
Explore the model protein function of Globin, understanding how its ability to bind O2 depends on a prosthetic group and the process of O2 binding and electron withdrawal. Learn about the role of distal histidine in inhibiting methemoglobin formation and enhancing selectivity for O2 over other gases.
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