3. Myoglobin Flashcards
describe hypoxia
deficiency of oxygen at tissues, can cause unconsciousness, cell death, brain death
give an example of a mammal which has an oxygen reservoir
whales
what is the job of the transporting molecule
to pick up oxygen from a place where oxygen is abundant and take it to a less abundant place
how do we measure oxygen abundance
partial pressure
what are the units for oxygen abundance
Torr or mm of Hg
what is atmospheric pressure of oxygen
760 torr
what is oxygen abundance at sea level
155.5 torr
how many amino acids in myoglobin
155 amino acids
describe the interior structure of myoglobin
almost entirely composed of non-polar residues
a haem group in the centre surrounded by non-polar residues except for 2 histidines
what does the haem group consist of in both Hb and Mb
iron atom (Fe^II) protoporphyrin IX
what does iron in haem bind to
4 nitrogen atoms in a plane
5th and 6th positions are free
what does oxygen binding result in
colour change
the haem electronic structure alters
explains the bright red colour of oxygenated blood in arteries and the dark purple colour of deoxygenated blood
name the two histidine residues either side of the haem molecule
Distal: His E7
proximal: His F8
which his residue is iron directly bound to
directly bound to F8 -> occupies the 5th position
NOT DIRECTLY BOUND TO E7
What is the function of histidine E7 (NOT BOUND)
occupies 6th coordination position
reduces affinity of carbon monoxide for binding
prevents other haemoglobins binding to the same oxygen molecule
how does his E7 prevent carbon monoxide binding
- carbon monoxide binds linearly tightly
- oxygen binds in a bent structure less tightly
- distal His forces bent binding of both, this is ideal for o2 but not CO
what is the p50 for myoglobin
2.75 torr
what does p50 mean
the concentration of oxygen where 50% of molecules have attached and 50% have given it up
what is the function of myoglobin
to transport oxygen into cells and releasing it where concentrations are low (e.g. mitochondria)
