Myoglobin Flashcards
What is myoglobin and what is it abbreviated to
It’s found in muscle
It binds to oxygen in muscles
Mb is its abbreviation
Write the equation for the forward and backward reaction between myoglobin and oxygen . What is this kind of reaction called
What is the dissociation constant
What is the equation for the fraction of myoglobin that has oxygen bound to it (initial and derived equation)
Underlined in purple
What is a saturation binding curve
Shows the fraction of myoglobin saturated with oxygen at a particular partial pressure of oxygen
Why does the curve on a saturation binding curve never reach the asymptote
Because in order for myoglobin to be completely saturated it would have to bind to an infinite amount of oxygen
What is a Torr
Unit for partial pressure
1 Torr= 133 Pa
What is the ratio of unprotonated to protonated histidine molecules
80% of histidine is unprotonated
20% of histidine is protonated
What are the two resonance forms for protonated histidines side chain? Show the displayed formula and the distribution of electrons in molecular orbitals
All of the atoms in histidine side chain are sp2 hybridised
It can have resonance forms because one of the nitrogen’s only have one elctron in its p orbital whereas the other nitrogen has two electrons in its p orbital
(When nitrogen that is bonded to hydrogen it has 2 electron sin its p orbital)
Show the displayed formula and the distribution of electrons in molecular orbitals of the two tautomers of histidine
Show the protonation reaction of histidines side chain
Show the deprotonation (of the protonated form) of histidines side chain
What are prosthetic groups
Non polypeptide parts that are added to a protein
What coordination does iron have and how are the ligands arranged around iron
What is a ligand according to chemistry’s definition
They are donors of a pair of electrons
How is porphyrin converted to heme
Label the alpha helices in this myoglobin. Where would heme be in myoglobin
How does oxygen bind to heme in myoglobin
Oxygen will be bound tilted, in the axial position to iron in heme
Why does oxygen bind to heme in myoglobin tilted
The distal histidine imposes a steric constraint on the binding site, preventing oxygen from binding perpendicularly to the plane of the heme. Instead, oxygen binds at an angle to avoid a steric clash with this histidine residue
The tilted binding allows for optimal orbital overlap between the iron atom and the oxygen molecule, which stabilizes the oxygen-heme complex
The distal histidine can form a hydrogen bond with the bound oxygen molecule. This hydrogen bond helps stabilize the oxygen in its tilted position.
makes it easier for myoglobin to release oxygen under low-oxygen conditions as this binding is less stable
What is heme
It is a the part of myoglobin that oxygen binds to
Heme is neutral
What is the partial pressure of the atmosphere and what percentage of the atmosphere is oxygen
20% of the atmosphere is oxygen
Partial pressure is 750 Torr
What is the partial pressure of oxygen in the atmosphere
150 Torr
What is the partial pressure of oxygen that muscles get from the blood stream
What is the solubility of oxygen in water and in muscle with myoglobin
What is a ligand according to biochemistry
A molecule that binds reversible, forming a complex with a protein
E.g oxygen is a ligand for Mb
What does it mean if Kd (dissociation constant) is high and if its low
