Haemoglobin-(Hb )( Respiratory pigment )
It is a globular protein present in RBC which helps in transport oxygen by the help of histidine . It is a kind of quaternary protein with 4 polypeptide chains (2 alpha and 2 beta ). The heme unit is a ring of atoms which carry an iron atom .(Fe 2+).
Heme binds o2 reversibly .
Co binds to heme more strongly than o2.
Haemoglobin has 2 states-
1.Oxyhaemoglobin (o2 bound 4 nos. )
2.Deoxy- haemoglobin (No O2 bound )
It is found in 2 major conformation forms -
1. R- form (Relaxed form )
-Fewer interactions ,more flexible
-Higher affinity for O2.
2. T-form (Tense form/ taut stage )
-More interactions ,more stable
-Lower affinity for O2.
Sickle cell disease is a genetic alteration that causes some hemoglobin molecules to be defective (the defective hemoglobin is termed hemoglobin S).
The iron atom in heme binds to the 4 nitrogen atoms in the centre of the porphyrin ring. Cooperative binding property( uptake of one ligand influences the affinities of the remaining unfilled binding sites. ) Haemoglobin is allosterically inhibited by CO2, protons( which is released from carbonic acid dissociation ) and the body needs oxygen .
Image source credit -http://cikgurozaini.blogspot.in/2011/09/carbon-dioxide-transport.html
When oxygen is bound to the first subunit of hemoglobin it change the quaternary structure of the protein this helps subsequent molecule of oxygen to bind to the next subunit. This phenomenon is called an allosteric (through space interaction).Iron atom is attached to the proximal histidine, this causes the local helix to move also.
http://www.s-cool.co.uk/a-level/biology/transport/revise-it/blog
Q1. When oxygen haemoglobin curve shift to left it represents -(2008 DEC)
a.Decrease in pH
b.Decrese in Co2 level
c.Rise in concentration of 2,3 BPG
d.more affinity for oxygen
Ans. c
Q2.The major role of 2,3 BPG formed during glycolysis in RBC is for haemoglobin is -
a.Increasing affinity for oxygen
b.Decreasing affinity for oxygen
c.Increasing affinity for Co2
d.Decreasing affinity for Co2
Ans. b
It is a globular protein present in RBC which helps in transport oxygen by the help of histidine . It is a kind of quaternary protein with 4 polypeptide chains (2 alpha and 2 beta ). The heme unit is a ring of atoms which carry an iron atom .(Fe 2+).
Heme binds o2 reversibly .
Co binds to heme more strongly than o2.
Haemoglobin has 2 states-
1.Oxyhaemoglobin (o2 bound 4 nos. )
2.Deoxy- haemoglobin (No O2 bound )
It is found in 2 major conformation forms -
1. R- form (Relaxed form )
-Fewer interactions ,more flexible
-Higher affinity for O2.
2. T-form (Tense form/ taut stage )
-More interactions ,more stable
-Lower affinity for O2.
Sickle cell disease is a genetic alteration that causes some hemoglobin molecules to be defective (the defective hemoglobin is termed hemoglobin S).
The iron atom in heme binds to the 4 nitrogen atoms in the centre of the porphyrin ring. Cooperative binding property( uptake of one ligand influences the affinities of the remaining unfilled binding sites. ) Haemoglobin is allosterically inhibited by CO2, protons( which is released from carbonic acid dissociation ) and the body needs oxygen .
Image source credit -http://cikgurozaini.blogspot.in/2011/09/carbon-dioxide-transport.html
When oxygen is bound to the first subunit of hemoglobin it change the quaternary structure of the protein this helps subsequent molecule of oxygen to bind to the next subunit. This phenomenon is called an allosteric (through space interaction).Iron atom is attached to the proximal histidine, this causes the local helix to move also.
Deoxy Hb ------- Oxy Hb
Image source credit -http://www.chemistry.wustl.edu/~edudev/LabTutorials/Hemoglobin/MetalComplexinBlood.html
Haemoglobin dissociation curve is S-shaped or sigmoidal.
when Hb combines to one Oxygen, its shape distorts slightly, and that makes it easier for the second Oxygen and so on upto 4th o2 molecule .Fourth can't combine with any more Oxygen molecules since 4 is the maximum number of O2 molecules that can combine with one molecule of Haemoglobin. This diagram reflects the idea:
when Hb combines to one Oxygen, its shape distorts slightly, and that makes it easier for the second Oxygen and so on upto 4th o2 molecule .Fourth can't combine with any more Oxygen molecules since 4 is the maximum number of O2 molecules that can combine with one molecule of Haemoglobin. This diagram reflects the idea:
Q1. When oxygen haemoglobin curve shift to left it represents -(2008 DEC)
a.Decrease in pH
b.Decrese in Co2 level
c.Rise in concentration of 2,3 BPG
d.more affinity for oxygen
Ans. c
Q2.The major role of 2,3 BPG formed during glycolysis in RBC is for haemoglobin is -
a.Increasing affinity for oxygen
b.Decreasing affinity for oxygen
c.Increasing affinity for Co2
d.Decreasing affinity for Co2
Ans. b
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