Lecture 11 - O2 transport and Storage by Haemoglobin and Myoglobin Pt. I Flashcards
What is the primary structure of Myoglobin?
150 amino acids
What is the secondary structure of Myoglobin?
8x alpha helices (labelled from A - H) and connecting loops
What is the tertiary structure of myoglobin?
globin fold with a hydrophobic pocket
What is the quaternary structure of myoglobin?
Monomeric (single polypeptide)
Where does the Haem bind to in myoglobin?
HisF8 (8th amino acid in helix F, which is a histidine residue)
What is Haem?
a prosthetic group, or cofactor
What is the basic structure of Haem?
four pyrrole rings linked together in a plane
How many coordinate bonds does iron (Fe) have?
6
What does the iron bind to in Haem?
4 binds to Nitrogen atoms in haem, 1 binds to a nitrogen atom of HisF8 in the globin, 1 binds to O2
Is the binding of oxygen to Fe2+ in haem reversible?
yes
What does a higher concentration of a molecule mean in spectroscopy?
less transmitted light and therefore higher absorbance
What does the beer lambert law convert?
absorbance of solution converted to concentration of solution
What is the purpose of spectroscopy?
Quantifying dissolved molecules based on the principle that different wavelengths are absorbed more or less efficiently
How can you determine if Haem is bound to an oxygen?
Haem has visible absorbance and therefore colour that differs between bright red oxyhaemoglobin (HbO2) and darker red deoxyhaemoglobin (Hb)
What else can change the shape of a spectroscopy spectrum?
colour, and nature of solute
How many globin subunits make up haemoglobin?
4 (usually 2 alpha, 2 beta)
how to the globin proteins in haemoglobin associate together?
non-covalently
What is the max number of O2 molecules that haemoglobin can hold at once?
4 (one per haem)
What is the common mechanism of Myo/Haemoglobin O2 binding?
- Haem Fe2+ is attached to globin protein by coordinate linkage to His F8
- Another His (from helix E) on opposite side of haem distorts binding of gas molecules to 6th coordination position on haem Fe2+
- This reduces binding affinity of oxygen making it easier to release oxygen to the muscle cell when needed
What is the function of myoglobin?
oxygen storage in tissues, needs to hold oxygen until it is required
What is the function of haemoglobin?
must acquire O2 from lungs and deliver to tissues, must bind O2 more weakly to release at correct time.
What type of curve is myoglobins binding curve?
hyperbolic
When is myoglobin saturated with oxygen?
at low partial pressure of oxygen
When does myoglobin release O2 to cells?
when cellular partial pressure of oxygen is very low