Lecture 18 Flashcards
How does CO2 affect oxygen release?
It promotes the release of oxygen
How do salt bridges effect the deoxy form of Hb?
They stabilize the deoxy form
What three things stabilize the deoxy from of Hb?
H+, BPG and salt bridges
What is a function of a protein determined by?
It’s structure
What substitution occurs with sickle cell anemia?
In the beta chain Glu6 is replaced is with valine
How does the substitution of glutamine for amino effect Hb?
It causes Hb molecules to aggregate into long polymers/fibres because a small hydrophobic surface patch is exposed
What is Fetal Hemoglobin responsible for?
Circulation of oxygen within a fetal bloodstream
What is the ranking of affinity for O2 of each hemoglobin?
Adult Hb < Fetal Hb < Mb
What are the four subunits of Fetal Hemoglobin?
It has two alpha and two gamma subunits
What are the gamma subunits in fetal Hb similar to?
The adult Beta subunit
What is the His143 in adult Hb substituted with in Fetal Hb?
The histidine is replaced with serine
What is the His143 involved in with adult Hb?
The binding of BPG
What is the difference between the Serine in fetal Hb instead of His 143 in adult Hb binding to Hb?
The serine has lower affinity of binding to BPG which means there is increased binding affinity for oxygen in Fetal hb
What is the main difference between fetal Hb and adult Hb?
Fetal Hb has a serine instead of a histidine meaning that it has less affinity to bind to BPG which is a negative allosteric effector. Because fetal Hb has less affinity for BPG it has higher affinity for O2
Which direction does fetal Hb shift the graph?
Shift left because it has a higher affinity for oxygen
Why are histidines used a lot?
Because it has a pka close to 7
What does His F8 (Proximal Histidine) do?
Binds to heme and coordinates the iron atom to prevent it from being oxidized. It also ensures the heme is strongly bound within the binding site
What does His E7 (Distal Histidine) do?
It forms an H bond with O2 and increases the specificity of O2 for oxygen and diminishes carbon monoxide affinity
What do the changes in protonation state in the central cavity or at the subunit interface do to the histidines?
They can lead to changes in how they bind to BPG or how they stabilize the T state
What is the Bohr effect about?
The pH dependance of O2 binding
How does low pH effect BPG?
It increases BPG binding
What is the equation of Nitrogen fixation?
N2 + 3H2 ➡️ NH3
What are enzymes involved in?
Increasing reaction rates
What are the two ways a reaction can be accelerated by?
- Adding heat
* Adding a catalyst (enzyme)
