Haemoglobin Flashcards
What is the structure of haemoglobin?
Has 2 alpha and 2 beta chains
Has 4 haem groups- can bind 4 O2 molecules
Glutamate 6 in B chain is hydrophilic- in sickle cell disease glutamate is replaced by valine which ih hydrophobic
What is Haem?
Made up of a protoporphyrin ring with central iron atom (Ferrous Fe2+)
Its bound within the pockets of globin proteins
What is globin?
Various types combine with haem to form different Hb molecules
Eight functional globin chains can be arranged into 2 clusters:
a- cluster : alpha and xi globin genes
B- cluster: beta, tau, delta and epsilon globin genes
What are the proportions of Hb in a healthy adult?
HbA: a2B2- 96-98%
HbA2: a2δ2- 1.5%-3.2%
HbF: a2Y2- 0.5-0.8%
What is 2,3-DPG?
2,3- diphosphoglycerate
Produced by rapoport-Luebering shuttle
Its an allosteric effector- modulates Hb oxygen affinity
Binds to beta globin chain in central cavity of Hb molecule
Has roles in response to anaemia, hypoxia and high altitude
What does the position of the Hb dissociation curve depend on?
H+ ion concentration
CO2 in RBCs
Structure of Hb
Concentration of 2,3-DPG
How does binding of oxygen molecule to Hb affect it?
Changes shape of Hb to make in easier for next O2 to bind- cooperativity mechanism
What is right shift?
Allows easier O2 delivery
Occurs when there’s high CO2 conc and low pH
Occurs when there’s high 2,3- DPG conc.
Occurs for HbS
Allows advanced unloading of O2 in metabolically active peripheral tissue
Increased skeletal muscle activity leads to increased PP of CO2 and reduces local blood pH
What is left shift?
Gives O2 less readily
Occurs for HbF and CO
Occurs when theres low 2,3-DPG conc.
Occurs when there’s low CO2 conc.
What is is the bohr effect?
Increase in CO2 PP. or decrease in blood pH results in lower affinity of Hb for O2 (wants to give O2 away)
It enhances oxygen delivery proportionally to metabolic activity of tissue
HbS has lower affinity for O2- right shift
HbF has higher affinity for O2- left shift
