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Units, Definitions and O 2 Availability OXYGEN. Units Barometric Pressure (mmHg) 760 mmHg = 1 atmosphere (atm) = 100 kPa Partial pressure= P gas a = Gas.

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Presentation on theme: "Units, Definitions and O 2 Availability OXYGEN. Units Barometric Pressure (mmHg) 760 mmHg = 1 atmosphere (atm) = 100 kPa Partial pressure= P gas a = Gas."— Presentation transcript:

1 Units, Definitions and O 2 Availability OXYGEN

2 Units Barometric Pressure (mmHg) 760 mmHg = 1 atmosphere (atm) = 100 kPa Partial pressure= P gas a = Gas a X P total Gas mix Usually given as a percentage

3 Calculate partial pressure of O 2 at Sea level Atmospheric pressure is 1 atm at sea level O 2 content ~ 21% Nitrogen78.08% Oxygen20.95% Water Vapor0 to 4 % Argon0.93% Carbon Dioxide0.036% Neon0.0018% Helium0.0005% Methane % Hydrogen % Nitrous Oxide % Ozone % What’s in our air? P gas a = Gas a X P total Gas mix

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

5 The respiratory pigments… Why are they important? Greatly increase O 2 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 2 HbO 2 Hemoglobin Oxyhemoglobin what happens when O 2 concentration is high? what happens when O 2 concentration is low? respiratory surface) systemic tissues) Why is reversible binding important?

8 O 2 -Hb dissociation curves: Describe activity of Hb at different P O 2 % of Hb binding sites bound % saturation PO2PO2

9 O 2 -Hb dissociation curves: Describe activity of Hb at different P O 2 % of Hb binding sites bound % saturation PO2PO2

10 O 2 -Hb dissociation curves: Describe activity of Hb at different P O 2 % saturation systemic respiratory surface

11 O 2 -Hb dissociation curves: Describe activity of Hb at different P O 2 % saturation systemic respiratory surface

12 “ Affinity ”- how tightly two molecules bind together Hb and O 2…. Do you want your hemoglobin to have really High or really Low affinity for O 2 ?

13 A trade-off * : Vs.  Optimal unloading of O 2 at tissues  Optimal loading of O 2 at respiratory surface * Hemoglobin’s affinity for O 2 determines which of these is favored

14 O 2 -Hb dissociation curves: P 50 P 50 is a measure of O 2 affinity % saturation P O 2 (mmHg) = P O2 at which pigment is 50% saturated with O 2

15 There are many different forms of hemoglobin  based on differences in protein portion  Show different affinities for O 2 =The product of different selective pressures (i.e., an example of adaptation)

16 O 2 -Hb dissociation curves: P 50 P 50 is a measure of O 2 affinity % saturation P O 2 (mmHg) Hb with a high affinity has a lower P 50 Animals that have Hb with high affinity: Hb is saturated when O 2 concentrations are relatively low b/c Hb will not release O 2 unless O 2 levels are very low this kind of Hb favors O 2 uptake (loading)

17 O 2 -Hb dissociation curves: P 50 P 50 is a measure of O 2 affinity % saturation P O 2 (mmHg) Hb with a low affinity has a higher P 50 Animals that have Hb with low affinity: Hb is only saturated when O 2 concentrations are relatively high b/c Hb is more likely to “let go” of O 2, even if O 2 levels are pretty high this kind of Hb favors O 2 delivery (offloading)

18 Animals native to high altitudes % saturation P 50 P O 2 (mmHg) Bar-headed goose

19 Animals native to high altitudes % saturation P 50 P O 2 (mmHg) Hb has higher O2 affinity Favors O 2 loading Bar-headed goose

20 One more respiratory pigment… Myoglobin (Mb)  essentially identical to Hb but only 1 heme unit  always in muscle cells  very high O 2 affinity

21 Comparing dissociation curves… myoglobin P 50 % saturation P O 2 (mmHg) hemoglobin

22 What is the function of myoglobin?  May serve as an O 2 reserve or store  Facilitates diffusion of O 2 into muscle  Very common in animals that live in periodically low O 2 environments

23 What I want you to know about respiratory pigments… Draw Hb-O 2 dissociation curve and explain why it has that shape Define and locate P 50 on a Hb-O 2 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… Northern Elephant Seal 1600 m! Sperm Whale 2000 m! Southern Elephant Seal 2 hours! 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 How do diving mammals deal with hypoxia? -need to be able to store O 2 for use when holding breath. Where can an organism “store” O 2 ? LungsBloodMuscle

29 Big lungs? - no…let lungs collapse! Major internal O 2 stores: Lungs - many deep divers exhale before diving ( % capacity)

30 Lung O 2 stores vs. Blood O 2 stores

31 Major internal O 2 stores: Blood Deep Divers have more blood for their body size than non-divers More blood holds more oxygen!

32 Major internal O 2 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

33 Comparing Total O 2 Stores:

34 What about our favorite curve?… Hb-O 2 dissociation % saturation P O2 Left shift or right shift? Shallow divers that rely more on lungs  Deeper Divers that rely more on blood stores of O 2 

35 Why??? Divers that rely on O 2 stores in lungs need high affinity Hb that will pull O 2 into blood even when the partial pressure of O 2 left in lungs has gotten really low. Divers that rely on blood stores of O 2 need lower affinity Hb that will allow O 2 to move into tissues even when partial pressure of O 2 in blood is really low.


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