Myoglobin & Hemoglobin Flashcards
True or False: myoglobin has a heme group with a Fe(III) ion in the center
False: the heme group has a Fe(II) ion in the center
Which form is the “T-state”?
Deoxy-Hb
Which form is the “R-state”?
Oxy-Hb
Between T and R states, which has a lower free energy?
T-state, the free energy is lower bc of the absence of oxygen.
What is the shape of the oxygen-binding curve of myoglobin?
Hyperbolic
What is the shape of the oxygen-binding curve of hemoglobin?
Sigmoidal (S-shape)
What does a hill coefficient of 1 mean?
No cooperativity
What does a hill coefficient of >1 mean?
There is cooperativity (the higher the hill coefficient, the steeper the curve)
Why would myoglobin be a poor oxygen transporter?
It binds oxygen really tightly so it wouldn’t let it go into the tissues when needed
In the O2 bound state of myoglobin, what coordinates the O2?
1 Histidine and Heme Fe
What is hemoglobin?
An oxygen transporter in the blood of most animals
True or false: Hemoglobin’s oxygen affinity is independent of pH
False. It is pH-dependent
True or false: Hemoglobin’s oxygen affinity can be regulated allosterically by BPG
True
True or false: Hemoglobin consists of 4 subunits with C2 symmetry
True
True or false: Heme becomes planar when O2 binds
True
True or false: The movement of the Fe2+ into the plane of the heme group and the greater planarity of the heme is the trigger of the T state to R state.
True
What is the model of hemoglobin allostery we discussed in class?
Symmetry model
True or false: BPG decreases at high altitudes
False
What is hemocyanin?
Hemocyanins are the oxygen binding proteins in blue blood (mollusks and arthropods)
What is the symmetry of Hemocyanin?
D3 symmetry
In the O2 bound state of hemocyanin what coordinates the O2?
2 Cu
True or false: Hemocyanin contains a heme group.
False
What is the genetic basis of sickle cell anemia?
Point mutation from Glu6 to Val6 in the B chain.
Sickle cell anemia causes deoxygenated hemoglobin tetramers to form long fibers. What promotes the sickling effect of HbS?
Increasing BPG, increasing blood CO2 (decreasing pH)
