Chapter 5 Flashcards
(36 cards)
Induced fit
conformational changes occur upon ligand binding
- increases affinity each other
- tighter binding
ligand
molecule that binds
landmuir isotherm equation
[PL]= [P]t + [L]t / Kd+ [L]t
Kd
- dissociation rate constant
- It equals the ligand concentration at which half of the protein in solution is saturated (or bound) to ligand
- inverse of Ka
Do you want a big or small Kd?
small Kd
-small dissociation rate means they have a high affinity for each other
if Kd is small it mean?
If it is small, that means you a LOW ligand concentration to achieve half protein saturation -> HIGH affinity
if Kd is big it means?
If it is large, that means you need a HIGH ligand concentration to achieve half protein saturation –> LOW affinity
What does the Kd depend on?
- Specificity between the protein and the ligand
2. pH and other environmental variables
Langmuir isotherm equation assumptions
- Binding is at equilibrium
- Binding is reversible
- Under most conditions [P]T ««< [L]T meaning the protein is saturated with ligand
- –So if the protein is saturated, and there is very little protein compared to the ligand most of the ligand is NOT bound to protein [L]T ~ [L]f
Which of the following statements is correct?
A. The higher the Kd, the higher the affinity between the protein and the ligand.
B. The fractional occupancy of the protein receptor increases as the binding affinity increases.
C. The concentration of the protein-ligand complex increases as the binding affinity decreases.
D. The concentration of protein-ligand complex increases as the rate of the dissociation reaction increases.
B. The fractional occupancy of the protein receptor increases as the binding affinity increases.
Myoglobin main function in mammals is
oxygen storage protein
A heme group is
- a porphyrin ring with an Fe atom
- prosthetic group
Is myoglobin tetrameric or monomeric
monomeric, it can only bind one oxygen
Where is myoglobin found?
the tissues
Which of the following statements is correct?
A. Myoglobin has four pyrole rings made of glutamine and succinyl-CoA
B. A heme group is a porphyrin ring with a Fe atom
C. Myoglobin has a similar primary structure to hemoglobin
D. If myoglobin was tetrameric instead of monomeric, it could be used to transport blood in the blood
E. Hemoglobin cannot transport CO2
B
Which of the following is NOT bound to iron in heme? A. 4 pyrole rings B. Distal histidine C. Proximal histidine D. O2 (if present)
B
Process of oxygen binding to myoglobin
Binding of O2 Fe goes from ferrous to ferric state, loosing electrons Soret band goes from 429 nm to 414 nm visible via UV-Visible range spectrophotometry
Hb is tetrameric or monomeric? How many oxygens can it bind?
Tetrameric, 4
Where is Hemoglobin found?
Hb is in the blood
pO2 in the __ is 13 pa (hemoglobin binds oxygen here and transports it to the tissues). while pO2 in the tissues is 4 pa (Hb must release O2)
lungs
where does Hb have a high affinity for O2
the lungs
positive cooperativity
first binding event increases affinity at remaining sites
-sigmodal
negative cooperativity
first binding decreases affinity at remaining sites
-increase then flatten
Hb shows _____ binding to O2
cooperative binding
