2. Blood Oxygen physically diffused by 0.2ml / 100 ml blood By Hb 20ml / 100ml blood So it’s the main function.

3. (Eckert, Fig. 13-1) Gas transfer system of vertebrates Low P O2 High P O2 High P CO2 Low P CO2

4. Main functions of blood * transport : *Oxygen and carbon dioxide »- nutrients »Hormones »Metabolites »Force ( hydraulic ) »Temperature Immunity Coagulation

5. Transport of O 2 in the blood  Respiratory pigments  After O 2 diffuses across the respiratory epithelium it is bound by a respiratory pigment  Respiratory pigments are complexes of proteins and metal ions

6. 1. hemoglobin 2. chlorocruorin 3. hemerythrin 4. hemocyanin 5.myoglobin Which in solution heavy, In cells lighter

7. Why Hb inside the cell VISCOSITY FIGURE 2,1 CHEMISTRY O2 BINDING

8. Chlorocruorin Class Polychaeta contain Fe green in low oxygen, red when saturated In solution

9. Hemocyanin some, molluscs, crustaceans and arachnids blue when oxygenated and colorless when deoxygenated contain Cu No porphyrin ring In solution

10. Hemerythrin Present in the blood of certain marine invertebrates (e.g. sipunculoid worms, polychaetes) Contains iron but not a porphyrin ring violet-pink when oxygenated, colorless when deoxygenated In cells

11. Hemoglobin (Hb)  Hemoglobin (Hb) Increases the carrying capacity of blood for O 2 Four protein (globin) chains, each attached to an iron-containing heme group Each heme group consists of a porphyrin ring with an iron atom in the center In humans, there are forms of globin: , , in adults (2 , 2  ) Form dimers  1  1  2  2 each Subunits bonded to other by links ( hydrogen,…)

12. Fe bind to the 4 N with coordinate covalent bond ( the bond e pair is formally contributed by only of the atoms forming the bonds) The fifth is his residue from globin The sixth is oxygen if exist To give oxyhemoglobin Each hb can carry 4 o Subunit interactions altered when Hb binds to O 2 or to other molecules

13. (Silverthorn, Fig. 16-7)

15. Hemoglobin loads up with oxygen in the lungs, forming oxyhemoglobin. As blood passes through the capillaries, some of the oxyhemoglobin releases oxygen and become deoxyhemoglobin. Hemoglobin - Carboxyhemoglobin: Hb saturated with CO

16. Partially saturated hemoglobin – when one to three hemes are bound to oxygen The rate that hemoglobin binds and releases oxygen is regulated by: –P O2, temperature, blood pH, P CO2, and the concentration of BPG (an organic chemical) These factors ensure adequate delivery of oxygen to tissue cells Hemoglobin (Hb)

17. Hemoglobin Fetal hemoglobin: gamma chains (not β) w/ higher affinity for O (enhance O transfer from mother to fetus) Affinity for CO = 200 x’s greater than for O

18. ( No, CO,H 2 S) poisoning even at low partial pressures Oxidation of Fe yields 3+ charge - ferric iron -methemyoglobin ( Met Hb) does NOT bind oxygen. ON THE SIXTH PART AWATER MOLECULE

19. Normally Fe may be oxidized ( few) So what : RBCs have a methemoglobin reductase, which convert small amount to – Hb normal.

20. Myoglobin Mb is a monomeric heme protein a store oxygen protein facilitate diffusion - found in skeletal & cardiac muscle - contain one heme binds one O2 Globin: - single polypeptide chain; 154 a.a.; 17.2 kD (monomer) - 8 helicies (label A-H) 20 hemoglobin 141= α Β= 146

21. Myoglobin Surface: polar; inside: non polar Fe in Mb is Fe2+ - ferrous iron - the form that binds oxygen Oxygen binds as the sixth ligand to Fe Higher affinity for O 2 than Hb

22. Myoglobin Oxidation of Fe yields 3+ charge - ferric iron -metmyoglobin ( MetMb) does NOT bind oxygen Cardiac muscle of diving mammals contain higher (8%) amounts of Myoglobin than most mammals (e.g. 0.5% for a dog)

23. Who's haven't: Antarctic Icefish body temperature:-1.7 o C

24. Who's haven't Antarctic ice fish lack pigment low metabolic needs = low metabolism high cardiac output, blood volume large heart O 2 solubility 0.3% Blood has lower viscosity –Easier to pump

26. Vertebrate Hemoglobin Polypetide chain Heme groups (Fe center) 2X 4 O 2 /Hb

27. How do respiratory pigments work? Reversibly Bind O 2 : heme group Hb + O 2 « HbO 2 To work effectively Hb should: 1.Bind O 2 at high PO 2 (lung, eqn. shifts right) 2.Release O 2 at low PO 2 (working tissue, eqn. shifts left)

28. Oxygen binding changes the Hb conformation – Without oxygen bound, Fe is out of heme plane – Oxygen binding pulls the Fe into the heme plane Fe pulls its His F8 ligand along with it The F helix moves when oxygen binds This change means little to Mb, but lots to Hb!

30. Mechanism of allosteric change Heme iron move <= 0.04 nm induces conformation change in Hb One alpha-beta pair moves relative to the other by 15 degrees upon oxygen binding This massive change is induced by movement of Fe by 0.039 nm when oxygen binds

31. Oxy and deoxy form represent 2 different conformation states - Hb binds O2 (from T R)

34. Cooperativity Binding 1 O 2 “loosens” conformation of Hb subunits –when “loose”, small changes in PO 2 can result in large changes in saturation “tight” “relaxed” O2O2

35. Cooperative oxygen binding and release is evident in the dissociation curve for hemoglobin. Where the dissociation curve has a steep slope, even a slight change in P O2 causes hemoglobin to load or unload a substantial amount of O 2. This steep part corresponds to the range of partial pressures found in body tissues. Hemoglobin can release an O 2 reserve to tissues with high metabolism.

36. Hemoglobin saturation plotted against P O2 produces a oxygen-hemoglobin dissociation curve 98% saturated arterial blood contains 20 ml oxygen per 100 ml blood (20 vol %) As arterial blood flows through capillaries, 5 ml oxygen are released Influence of P O2 on Hemoglobin Saturation

37. Hb-O 2 Dissociation Curve Desaturated “tight” Cooperativity “loose” Saturation PO 2

38. Fig 42.28 Hb + O 2 HbO 2 Fig 42.27 1 12 2 (resting tissue) 3 (exercising musc.)

39. Hemoglobin is almost completely saturated at a P O2 of 70 mm Hg Further increases in P O2 produce only small increases in oxygen binding Oxygen loading and delivery to tissue is adequate when P O2 is below normal levels Hemoglobin Saturation Curve

40. Only 20–25% of bound oxygen is unloaded during one systemic circulation If oxygen levels in tissues drop: –More oxygen dissociates from hemoglobin and is used by cells –Respiratory rate or cardiac output need not increase Hemoglobin Saturation Curve

41. Figure 22.7 Respiratory pigments display hyperbolic or sigmoid oxygen equilibrium curves (Part 1)

43. Details of Mb-O2 binding site Proximal Histidine: coordinated to heme iron