What are prosthetic groups?
molecules that are permanently attached to a protein
What are details about the heme prosthetic group and why is it important?
central iron surrounded by porphyrin ring, needed to bind to oxygen reversibly
Where does the heme sit within the myoglobin?
in a deep hydrophobic cleft
What are the two important amino acid residues in myoglobin that are important?
His F8 interacts with the heme group
His E7 interacts with oxygen
What are the primary functions of myoglobin?
improves oxygen solubility to facilitate diffusion in muscle
prevents heme oxidation
Prevents CO binding
What is fractional saturation for?
to describe how much oxygen is bound to myoglobin
What is the relationship between p50 and affinity for oxygen?
High p50 means low affinity for oxygen
Low p50 means high affinity for oxygen
What is the difference between myoglobin and hemoglobin shape wise?
myoglobin is a monomer, while hemoglobin is a tetramer that has 2 conformations
What is the structure of hemoglobin?
two alpha-beta dimers that are symmetrical
In hemoglobin, what happens when oxygen binds?
There is a conformational change, the beta subunits get closer together
What is the Hill constant used for?
estimates cooperativity between binding sites in hemoglobin
In a Hill Plot, what are the axis and what does the slope represent?
x axis: log pO2, y axis: log (yO2/1-yO2)
slope > 1 means positive cooperativity
slope = 1 means no cooperativity
What are the two states that hemoglobin can exist in?
T state favors de-oxy hemoglobin
R state favors oxy hemoglobin
What happens with the tertiary structures as hemoglobin goes from T state to R state?
subunits shift left or right, ion pairs break
What are ways to lower the affinity of hemoglobin for oxygen and promote release?
H+, CO2, BPG
What happens in the Bohr effect for protons?
Lower pH promotes T state
Higher pH promotes R state
What is the Bohr effect for CO2 in tissues and lungs?
Tissues: high amounts of CO2 drop the pH, making the T state more favorable
Lungs: low amounts of CO2 raises the pH, making the R state more favorable
What does BPG do to hemoglobin?
can only bind to T state in the central cavity, promotes oxygen release
