Presentation on theme: "Units, Definitions and O2 Availability"— Presentation transcript:
1Units, Definitions and O2 Availability OXYGENUnits, Definitions and O2 Availability
2Units Barometric Pressure (mmHg) 760 mmHg = 1 atmosphere (atm) = 100 kPaPartial pressure=Pgas a = Gasa X PtotalGasmixUsually given as a percentage
3Calculate partial pressure of O2 at Sea level Pgas a = Gasa X PtotalGasmixWhat’s in our air?Nitrogen78.08%Oxygen20.95%Water Vapor0 to 4 %Argon0.93%Carbon Dioxide0.036%Neon0.0018%Helium0.0005%Methane%Hydrogen%Nitrous Oxide%Ozone%Atmospheric pressure is 1 atm at sea levelO2 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
4The respiratory pigments… Why are they important?100X increase!
5The respiratory pigments… Why are they important?Greatly increase O2 carrying capacity of blood100X increase!
6Hemoglobin (Hb) 4 heme units: = 1 iron-porphyrin + 1 protein “heme” “globin”(1 Hb can carry 4 oxygen molecules)
7Hb binds oxygen reversibly… Hb + O HbO2Hemoglobin OxyhemoglobinWhy is reversible binding important?what happens when O2 concentration is high?respiratory surface)what happens when O2 concentration is low?systemic tissues)
8O2-Hb dissociation curves: Describe activity of Hb at different PO2% saturationPO2% of Hb binding sites bound
9O2-Hb dissociation curves: Describe activity of Hb at different PO2% saturationPO2% of Hb binding sites bound
10O2-Hb dissociation curves: Describe activity of Hb at different PO2% saturationPO2@ systemic tissues@ respiratory surface
11O2-Hb dissociation curves: Describe activity of Hb at different PO2% saturationPO2@ systemic tissues@ respiratory surface
12Hb 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 surfaceVs.Optimal unloading of O2 at tissues* Hemoglobin’s affinity for O2 determines which of these is favored
14O2-Hb dissociation curves: P50 is a measure of O2 affinity% saturationPO2 (mmHg)204060801003090= PO2 at which pigment is 50% saturated with O2P50
15There are many different forms of hemoglobin =The product of different selective pressures(i.e., an example of adaptation)based on differences in protein portionShow different affinities for O2
16O2-Hb dissociation curves: P50 is a measure of O2 affinityHb with a high affinity has a lower P50Animals that have Hb with high affinity: Hb is saturated when O2 concentrations are relatively lowb/c Hb will not release O2 unless O2 levels are very lowthis kind of Hb favors O2 uptake (loading)% saturationPO2 (mmHg)204060801003090P50
17O2-Hb dissociation curves: P50 is a measure of O2 affinityHb with a low affinity has a higher P50Animals that have Hb with low affinity: Hb is only saturated when O2 concentrations are relatively highb/c Hb is more likely to “let go” of O2, even if O2 levels are pretty highthis kind of Hb favors O2 delivery (offloading)% saturationPO2 (mmHg)204060801003090P50
18Animals native to high altitudes % saturationP50PO2 (mmHg)406080100309020Bar-headed goose
19Animals native to high altitudes Favors O2 loading10080Bar-headed goose60% saturationHb has higher O2 affinity40P5020306090PO2 (mmHg)
20One more respiratory pigment… Myoglobin (Mb)essentially identical to Hb but only 1 heme unitalways in muscle cellsvery high O2 affinity
22What is the function of myoglobin? May serve as an O2 reserve or storeFacilitates diffusion of O2 into muscleVery common in animals that live in periodically low O2 environments
23What I want you to know about respiratory pigments… Draw Hb-O2 dissociation curve and explain why it has that shapeDefine and locate P50 on a Hb-O2 dissociation curveDraw 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.
26Some diving records… Southern Elephant Seal Northern Elephant Seal 2 hours!Sperm Whale2000 m!It is pretty astounding what diving mammals can doEven with scuba gear humans are far behind.Not sure if this record is currentDr. Sylvia Earle375 meters, 1230 ft(with scuba gear)
27Free Diving (no scuba tank) “no limits” record = 171 m ( ft)“unassisted constant ballast” record = 65 m ( ft)
28Where 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?LungsBloodMuscleIf you are going to hold your breath you need a reserve supply of Oxygen to use until you can breath againWe are going to talk about the relative importance and adaptations on each of these stores
29Major 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 wallWHY wouldn’t you want to store air there if you can?
30Lung O2 stores vs. Blood O2 stores Describe axes,Q: what is the point that this graph makes?Q: Compare shallow divers to deep
31Major internal O2 stores: Blood Deep Divers have more blood for their body size than non-diversMore blood holds more oxygen!So Blood appears to be more impt than lungs in deep diversDeep divers actually have more blood (for their body size) than shallow or non-diversPercent fat inc this relationship
32Major 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 HumanBlood has different properties- it can hold more Oxy- see graph 1Describe graph
33Comparing 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 lungsDeeper Divers that rely more on blood stores of O2 % saturationWhat shift do you predict in diving mammals?WHY- How does it change affinity?What does it favor?PO2
35Why???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.