1. Biochemistry Sixth Edition
Berg • Tymoczko • Stryer
Chapter 7:
Hemoglobin:
Portrait of a Protein in Action
Copyright © 2007 by W. H. Freeman and Company

2. Erythrocytes (Red cells)

3. Hemoglobin and Myoglobin
These are conjugated proteins. A simple protein has only a polypeptide chain. A conjugated protein has a non-protein part in addition to a polypeptide component. Both myoglobin and hemoglobin contain heme.
Myoglobin daltons (monomeric) 153 amino acids
Hemoglobin daltons ( tetrameric) a-chain has 141 amino acids b-chain has 146 amino acids

4. Hemoglobin O2 carrying capability
Erythrocytes/ml blood: 5 billion ( 5 x 109 )
Hemoglobin/red cell: million ( 2.8 x 108 )
O2 molecules/hemoglobin: 4
O2 ml blood: (5 x 109)(2.8 x 108)(4) = (5.6 x 1018)
or (5.6 x 1020) molecules of O2/100 ml blood

5. Myoglobin, monomeric

6. Aromatic Heme

7. Iron in Hemoglobin binding O2

8. Hemoglobin, a2b2 tetramer

9. O2 binding: Hemoglobin & Myoglobin
P50 = 2 torr
P50 = 26 torr

10. O2 transport capability, a comparison

11. Resting state vs exercise

12. O2 Binding Changes 4o Structure

13. Decreasing O2 affinity 2,3-bisphospho-glycerate (2,3-BPG)
Lowers the affinity of oxygen for Hemoglobin

14. 2,3-bisphosphoglycerate (2,3-BPG)
The binding pocket for BPG contains 4 His and 2 Lys

15. Binding of bisphosphoglycerate

16. Oxygen Affinity of Fetal Red Blood Cells
Fetal red blood cells have a higher oxygen affinity than that of maternal red blood cells because fetal hemoglobin does not bind 2,3-BPG as well as maternal hemoglobin does

17. The Bohr Effect Bohr Effect:
Lowering the pH decreases the affinity of oxygen for Hb

18. Loss of O2 from Hemoglobin
Carbamate:
CO2 combines with NH2 at the N-terminus of globins

19. Carbamate formation
Covalent binding at the N-terminus of each subunit

20. Sickle Cell due to Glu 6  Val 6