1. Units, Definitions and O2 Availability
OXYGEN
Units, Definitions and O2 Availability

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

3. Calculate partial pressure of O2 at Sea level
Pgas a = Gasa X Ptotal
Gasmix
What’s in our air?
Nitrogen
78.08%
Oxygen
20.95%
Water Vapor
0 to 4 %
Argon
0.93%
Carbon Dioxide
0.036%
Neon
0.0018%
Helium
0.0005%
Methane %
Hydrogen %
Nitrous Oxide %
Ozone %
Atmospheric pressure is 1 atm at sea level
O2 content ~ 21%
If you go up in elevation (X ft elevation is 0.5 atmosphere), what happens to the partial pressure?
O2 is still 21% of the atmosphere, but there are less air molecules per area. So 21% * 0.5 = 10.5

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

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

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

7. Hb binds oxygen reversibly…
Hb + O HbO2
Hemoglobin Oxyhemoglobin
Why is reversible binding important?
what happens when O2 concentration is high?
respiratory surface)
what happens when O2 concentration is low?
systemic tissues)

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

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

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

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

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

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

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

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. O2-Hb dissociation curves:
P50 is a measure 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 O2 uptake (loading)
% saturation
PO2 (mmHg) 20 40 60 80
100 30 90
P50

17. O2-Hb dissociation curves:
P50 is a measure 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 O2 delivery (offloading)
% saturation
PO2 (mmHg) 20 40 60 80
100 30 90
P50

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

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

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

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

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. Some diving records… Southern Elephant Seal Northern Elephant Seal
2 hours!
Sperm Whale
2000 m!
It is pretty astounding what diving mammals can do
Even with scuba gear humans are far behind.
Not sure if this record is current
Dr. Sylvia Earle
375 meters, 1230 ft
(with scuba gear)

27. Free Diving (no scuba tank)
“no limits” record = 171 m ( ft)
“unassisted constant ballast” record = 65 m ( ft)

28. Where can an organism “store” O2?
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?
Lungs
Blood
Muscle
If you are going to hold your breath you need a reserve supply of Oxygen to use until you can breath again
We are going to talk about the relative importance and adaptations on each of these stores

29. Major internal O2 stores: Lungs
Big lungs?
- no…let lungs collapse!
- many deep divers exhale before diving ( % capacity)
When you are asked to hold your breath what do you do?
What do you predict about the lungs of diving mammals?
Chest wall
WHY wouldn’t you want to store air there if you can?

30. Lung O2 stores vs. Blood O2 stores
Describe axes,
Q: what is the point that this graph makes?
Q: Compare shallow divers to deep

31. Major internal O2 stores: Blood
Deep Divers have more blood for their body size than non-divers
More blood holds more oxygen!
So Blood appears to be more impt than lungs in deep divers
Deep divers actually have more blood (for their body size) than shallow or non-divers
Percent fat inc this relationship

32. Major internal O2 stores: Blood
Oxygen carrying capacity (Hb)
- more Hb per red blood cell (RBC)
- more RBC’s per ml blood (higher Hematocrit)
Weddell Seal Harbor seal Human
Blood has different properties- it can hold more Oxy- see graph 1
Describe graph

33. Comparing Total O2 Stores:
Along x -axis depth of diving (diving ability) increases

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
What shift do you predict in diving mammals?
WHY- How does it change affinity?
What does it favor?
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.