Units, Definitions and O 2 Availability

1. Units, Definitions and O2 Availability OXYGEN

2. Usually given as a percentage Units Barometric Pressure 760 mmHg = 1 atmosphere (atm) = 100 kPa Partial pressure= Pgas a = Gasa X Ptotal Gasmix

3. Pgas a = Gasa X Ptotal Gasmix Calculate partial pressure of O2 at Sea level • Atmospheric pressure is 1 atm at sea level • O2 content ~ 21% What’s in our air?

4. The respiratory pigments… Why are they important? 100X increase!

5. Greatly increase O2 carrying capacity of blood The respiratory pigments… Why are they important? 100X increase!

6. = 1 iron-porphyrin + 1 protein “heme” “globin” (1 Hb can carry 4 oxygen molecules) Hemoglobin (Hb) • 4 heme units:

7. Hb binds oxygen reversibly… Hb + O2HbO2 HemoglobinOxyhemoglobin Why is reversible binding important? • what happens when O2 concentration is high? (@ respiratory surface) • what happens when O2 concentration is low? (@ systemic tissues)

8. % of Hb binding sites bound % saturation PO2 O2-Hb dissociation curves: Describe activity of Hb at different PO2

9. % of Hb binding sites bound % saturation PO2 O2-Hb dissociation curves: Describe activity of Hb at different PO2

10. % saturation @ systemic tissues @ respiratory surface PO2 O2-Hb dissociation curves: Describe activity of Hb at different PO2

11. % saturation PO2 O2-Hb dissociation curves: Describe activity of Hb at different PO2 @ systemic tissues @ respiratory surface

12. “Affinity”- how tightly two molecules bind together Hb and O2…. Do you want your hemoglobin to have really High or really Low affinity for O2?

13. Optimal loading of O2 at respiratory surface • Optimal unloading of O2 at tissues A trade-off*: Vs. * Hemoglobin’s affinity for O2 determines which of these is favored

14. 100 80 % saturation 60 40 P50 20 0 30 60 90 PO2 (mmHg) O2-Hb dissociation curves: P50is ameasure of O2 affinity = PO2 at which pigment is 50% saturated with O2

15. There are many different forms of hemoglobin =The product of different selective pressures (i.e., an example of adaptation) • based on differences in protein portion • Show different affinities for O2

16. 100 80 % saturation 60 40 20 0 30 60 90 PO2 (mmHg) O2-Hb dissociation curves: P50is ameasure of O2 affinity • Hb with a high affinity has a lower P50 • Animals that have Hb with high affinity: Hb is saturated when O2 concentrations are relatively low • b/c Hb will not release O2 unless O2 levels are very low • this kind of Hb favors O2uptake (loading) P50

17. 100 80 % saturation 60 40 20 0 30 60 90 PO2 (mmHg) O2-Hb dissociation curves: P50is ameasure of O2 affinity • Hb with a low affinity has a higher P50 • Animals that have Hb with low affinity: Hb is only saturated when O2 concentrations are relatively high • b/c Hb is more likely to “let go” of O2, even if O2 levels are pretty high • this kind of Hb favors O2delivery (offloading) P50

18. 100 80 60 % saturation 40 P50 20 0 30 60 90 PO2 (mmHg) Animals native to high altitudes Bar-headed goose

19. Favors O2 loading Animals native to high altitudes 100 80 Bar-headed goose 60 % saturation Hb has higher O2 affinity 40 P50 20 0 30 60 90 PO2 (mmHg)

20. One more respiratory pigment… Myoglobin (Mb) • essentially identical to Hb but only 1 heme unit • always in musclecells • very high O2 affinity

21. myoglobin hemoglobin 100 80 % saturation 60 40 P50 P50 20 0 30 60 90 PO2 (mmHg) Comparing dissociation curves…

22. What is the function of myoglobin? • May serve as an O2 reserve or store • Facilitates diffusion of O2 into muscle • Very common in animals that live in periodically low O2 environments

23. What I want you to know about respiratory pigments… • Draw Hb-O2 dissociation curve and explain why it has that shape • Define and locate P50 on a Hb-O2 dissociation curve • Draw dissociation curve for Hb’s with different affinities and give physiological and ecological relevance of difference in affinity. • Compare dissociation curves for Hb and myoglobin and give physiological relevance.

24. DIVING PHYSIOLOGY

25. Diving Physiology- marine mammals • Cetaceans (whales, dolphins and porpoise) • Pinnipeds (seals, sea lion, walrus) • Sirenia (manatee, dugong) • Mustelidae (sea otter) • Carnivora (Polar Bear)

26. Sperm Whale 2000 m! Some diving records… Southern Elephant Seal Northern Elephant Seal 1600 m! 2 hours! Dr. Sylvia Earle 375 meters, 1230 ft (with scuba gear)

27. “no limits” record = 171 m (561.02 ft) Free Diving (no scuba tank) “unassisted constant ballast” record = 82m (269 ft)

28. Lungs Blood Muscle How do diving mammals deal with hypoxia? -need to be able to store O2 for use when holding breath. Where can an organism “store” O2?

29. Major internal O2 stores: Lungs • Big lungs? - no…let lungs collapse! - many deep divers exhale before diving (20 - 60% capacity)

30. Lung O2 stores vs. Blood O2 stores

31. Major internal O2 stores: Blood Deep Divers have more blood for their body size than non-divers More blood holds more oxygen!

32. Weddell Seal Harbor seal Human Major internal O2 stores: Blood • Oxygen carrying capacity (Hb) - more Hb per red blood cell (RBC) - more RBC’s per ml blood (higher Hematocrit)

33. Comparing Total O2 Stores:

34. What about our favorite curve?… Hb-O2 dissociation Left shift or right shift? Shallow divers that rely more on lungs  Deeper Divers that rely more on blood stores of O2  % saturation PO2

35. Why??? • Divers that rely on O2 stores in lungs need high affinity Hb that will pull O2 into blood even when the partial pressure of O2 left in lungs has gotten really low. • Divers that rely on blood stores of O2 need lower affinity Hb that will allow O2 to move into tissues even when partial pressure of O2 in blood is really low.