10 Myoglobin & Haemoglobin Flashcards
(34 cards)
What is the structure of a Haem group?
Protoporphyrin ring and an Fe atom bound to 4 N atoms of the ring.
How many molecules of oxygen does each haem group bind to?
1
What is the structure of myoglobin?
Single polypeptide chain with 1 haem group that can bind 1 molecule of oxygen
How does oxygen binding to haemoglobin or myglobin alter their structure?
Causes movement of Fe into the plane of the ring, causing a small change in protein conformation. More important in haemoglobin.
What shape is the myoglobin dissociation curve?
Hyperbolic
What shape is the oxygen dissociation curve of haemoglobin?
Sigmoidal
Outline the structure of haemoglobin.
A tetramer consisting of 2 alpha, and 2 beta polypeptide chains.
4 haem groups , can bind 4 molecules of oxygen.
How does oxygen binding alter haemoglobin?
It causes a structural change, which promotes stabilisation of the high affinity R state, with haem groups more exposed.
Why is the haemoglobin binding curve sigmoidal?
It las low affinity for oxygen at low partial pressures (in tissues).
It has high affinity for oxygen at high partial pressures (in lungs). So it will pick up oxygen in lungs and release it in tissues.
What does ‘cooperative binding of oxygen’ mean?
The binding affinity for oxygen increases as more oxygen molecules bind to Hb subunits. First O2 molecule binding is low affinity and hard, but last is high affinity and very easy.
Which has a higher affinity for oxygen, myoglobin or haemoglobin?
Myoglobin
How does 2,3 Bisphosphoglycerate (BPG) impact oxygen binding?
It lowers the affinity of Hb for oxygen, shifting the curve right. Allosteric inhibitor.
Where is BPG found?
In red blood cells
How many BPG molecules bind to a haemoglobin tetramer?
1 per tetramer
When will BPG concentration be increased?
At high altitudes where they is less O2 in the atmosphere,as it promotes O2 release at the tissues.
Which amino acid residues does BPG interact with?
It is negatively charged so tends to interact with positive hist and lys residues.
Other than BPG, what else can bind to haemoglobin molecules to regulate oxygen transport?
Co2 and H+.
What effect does CO2 and H+ have on haemoglobin?
Lowers the affinity of haemoglobin for oxygen. The bohr effect,rightward shift.
Why is it useful that CO2 and H+ cause oxygen release to tissues?
Metabolically active tissues produce large amounts of H+ and CO2 (lactate in anaerobic resp)
Bohr effect ensures the delivery of oxygen is coupled with demand.
Name 3 allosteric inhibitors of haemoglobin?
- BPG
- H+
- Co2
Why is carbon monoxide poisonous?
It has much higher affinity for Hb than oxygen does, it binds tightly and blocks oxygen transport as it doesn’t dissociate.
CO binding also increases the affinity for oxygen of the other subunits, preventing oxygen release into tissues.
What level does carboxyhaemoglobin binding become fatal?
COHb > 50%
How can you reverse carbon monoxide poisoning?
Physically increase O2 to very high levels.
How is HBA1c formed and what does it indicate?
Glycosylation of HbA, it is a diabetes marker and indicates what glucose levels have been like over the past few weeks or months.
