Lecture 17: Midterm cut-off Flashcards
What kind of effector is O2 to hemoglobin?
O2 is a positive homoallosteric activator of Hb
What is the affinity for oxygen in the T state and in the R state?
T state - low oxygen affinity
R state - high oxygen affinity
Which principle does oxygen being a homosteric activator of Hb depict?
Le Chatelier’s principle
What is positive cooperativity?
When the first thing is difficult to do but subsequent events become easier
What is the iron atom in hemes orientation in the T state and in the R state?
Once oxygen binds and is in the heme becomes R state the Fe iron moves in to the porphyrin plane. In the tense state the iron atom is not in the porphyrin plane
What happens after the iron moves into the plane of the porphyrin plane when O2 binds?
The Proximal (F8) histidine also moves
What happens after the proximal histidine moves when the Fe moves into the porphyrin plane?
The entire F helix then moves
Why does helix F cause conformational changes to other hemoglobin when O2 binds?
Because it it in the subunit interface between one subunit of hemoglobin other subunits of hemoglobin
What are the events that occur that cause cooperative binding in hemoglobin?
O2 binds this causes Fe2+ to move into the plane of heme. The Fe2+ is connected to histidine F8 so it also moves. This causes elix F to move. This then cause the subunit interface to move which affects other subunits
What does a sigmoidal graph indicate about a ligand?
It indicates that a ligand is a homoallosteric positive effector
Which level of structure does oxygen binding to hemoglobin effect?
Tertiary structure
What is a heteroallosteric (-) effector?
Something that is not the ligand of interest that binds and diminishes binding of the ligand of interest
What is a heteroallosteric (+) effector?
Something that is not the ligand of interest that binds and causes increased binding of the ligand
What effector will shift a binding curve to the left (increase binding)?
A heteroallosteric positive effector
What effector will shift a binding curve to the right (decrease binding)?
A heteroallosteric negative effector
