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CHMI 2227EBiochemistry I

Proteins:- Quaternary structure

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Quaternary structure

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Quaternary structure

Porin: a trimeric membrane-bound protein

hydrophobic

hydrophilic

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Quaternary structureHemoglobin

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Quaternary structureHemoglobin HbA vs myoglobin

HbA Myoglobin

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Quaternary structureOxygen binding by Hb and myoglobin

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Quaternary structureOxygen binding by Hb and myoHb

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Quaternary structureOxygen binding by Hb and myoHb

A

B

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Quaternary structureOxygen binding by Hb and myoHb

A

B

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Quaternary structureO2 binding changes the 3-D shape of Hb

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Quaternary structureO2 binding changes the 3-D shape of Hb

http://upload.wikimedia.org/wikipedia/commons/0/07/Hb-animation2.gif

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Quaternary structureHb is an allosteric protein

O2

O2

O2 O2

O2

O2 O2 O2 O2

O2O2

Low affinity High affinity Saturated

O2 O2 O2

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Quaternary structureWhy Hb is allosteric, while Myoglobin is not?

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The Bohr effecthttp://w

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.aw-bc.com

/mathew

s/ch07/fi7p16.htm

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Gas exchangeIn the tissues

TissuesErythrocytes

Glucose + O2

ATP

CO2

CO2H2O

Carbonic anhydrase

H2CO3

HCO3-

H+

Plasma

HCO3-

(to lungs)

Hb-4O2

Hb-H+

4O2 4O2

H2O + Cl-

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Gas exchangeIn the lungs

LungsErythrocytes

CO2H2O

Carbonic anhydrase

H2CO3

HCO3-

H+

Plasma

HCO3-

Hb-4O2

Hb-H+

4O2 O2

H2O + Cl-

CO2

Air

CO2

O2