Apr 7th Monday Gas Exchange o T Air pressure is dependent on PV nRT Having get the air in there O2 in and CO2 out but how exactly does gas exchange occur The gas pressure The pressure is dependent on T For situations inside lungs bloodstream and cells the effects of temperature is not important because under normal physiological conditions the Ts of these places are not changing Sure we can have hypothermic and hot and the pressure will be affected but for our regular physiology this effector is a nonissue Also there is the weather issue like the wind issue because we change the temperature relative to the tube areas and a lot of gas movement happens Gases present in partial pressure Px Typically 79 N2 little CO2 and H2O PO2 160 mm Hg 21 O2 PCO2 0 3 mm Hg Measure in a particular number percentage is harder to be dealt with here we can see the pressure directly The air is a composition of different gases Air equals nitrogen is a better description than that air equals oxygen N2 80 A little bit of CO2 A little water changing with location on the earth the season and the temperature Oxygen 20 Gases density based on Px gradients gas moves from high to low o Into and out if liquids o Between liquids Think of the partial P If we think of the amount of gas pressure created in this room as 100 79 or 80 will be N2 Why should we care Why not stick with concentrations Need two things for concentration calculations the number and the volume Calculating the volume of the blood is not desired P is easier to work with Between alveoli and blood o For blood returning to the lungs PCO2 46 mm Hg PO2 40 mm Hg o For air in alveoli PCO2 40 mm Hg PO2 105 mm Hg We expect the volume of deoxygenated blood coming back to the lungs to be bigger because it brings the CO2 the waste product back For oxygen we expect there is more in the alveoli so the gas exchange can occur For O2 goes from 105 mm Hg to 40 mm Hg goes to the blood Deoxygenated blood is not equal to unoxygenated blood DB still have oxygen in there o Therefore O2 blood into the blood then to the tissue CO2 alveoli o But why are values off in alveoli Why different from right in front of your face PCO2 40 not 0 3 PO2 105 not 160 100 because of the residual volume staying in the lungs Raises the CO2 levels and lowers the O2 levels Cannot get expel all the used air After birth the number will never be equal CO2 high to low Make that CO2 in the Krebs cycle and breath them out Gas Transport figure 13 27 O2 in blood nonpolar O2 and polar blood don t dissolve well only 1 dissolved 1 Dissolved but poorly soluble 2 Reversely bound to Hemoglobin Hb in the RBCs 99 O2 Hb 4 identical subunits protein made up of 4 subunits Fe shares e with O2 share the e because we want the O2 to stay in molecule form not with any fewer or more e s don t want to convert to ions then back to O2 need the O2 to participate in cell metabolism Transport bus just at different spots o Cooperativity between units the protein change shape upon binding 1st O2 binding increases the affinity at others by changing the shape loaded up with 4 O2 want the Hb to be filled up 1st O2 unbinding decreases the affinity at others 4 or 0 o Increase O2 transferred the actual transferring of oxygen in the figure A is the alveoli B is the blood Have 12 of O2 and the gradient is only about the free O2 6 in each side balance no breathing If 12 come in only get 6 50 transferred can we do better by Hb See with Hb 4 in the blood is binded to Hb and free O2 is 2 so we have the gradient again Then 8 sites covered 10 got transferred higher efficiency o Factors decrease affinity for O2 CO2 at a separate binding site to O2 once binding changes the shape of the oxygen site and caused the oxygen to come off makes it harder to bind O2 H lower the pH O2 comes off the Hb increase T change the shape of protein just think of the boiled egg DPG associated with glycolysis where glycolysis happens there is DPG just change the shape and kicks off the oxygen all these four kicks off O2 but not by interacting with the O2 binding sites themselves just by changing the shape and thus impact binding CO actually bind to the O2 site a competitor taking up the spot Hb is in favor of CO by many folds greater What is something we have discussed that ties the four things together Just think about the first four but not CO Hemoglobin saturation curve figure 13 26 o Hb saturation directly dependent on PO2 direct relationship At increased PO2 high number pick up Ls Highest affinity Hb is going to take the O2 at lungs At decreased PO2 drop off Ts Drop down the level of O2 less than 100 kicked off some O2 then have deoxygenated blood come back o Venous reserve unused returning O2 Still has tons of O2 attached to the Hb back to the heart then back to the lungs CPR today is just to get the convection going just the chest compression part not willing to go lip to lip and breath into them and they have their venous reserve just get their convection going circulating the blood going until the first aid responders come The rate of people willing to save has doubled Activity level increases VR down venous reserve inverse relationship o Can PO2 0 In cells yes We can have 0 oxygen in the cells In blood no We cannot have unoxygenated blood has O2 gradient so the O2 will flows to the blood to bring back the balance so the only time this could happen is there is no oxygen in your system but you cannot survive every cell in your body in anaerobic environment making just 2 ATPs per glucose is not enough Carbon dioxide CO2 o More soluble than O2 Still nonpolar but not as nonpolar as O2 do not fighting against the blood as O2 o 10 free CO2 30 carried on Hb o Other 60 CO2 H2O HCO3 H O2 is either free or binded to Hb Converted to bicarbonate HCO3 soluble Question for Wednesday why do we want it to be converted to bicarbonate Apr 9th Wednesday Plasma buffered system due to Hb and albumin Venous pH arterial pH tissues making CO2 Offloaded in lungs HCO3 H CO2 H2O Problems o Hypoventilation too little CO2 not releases Increased arterial PCO2 increased H respiratory alkalosis Causes decreased O2 on Hb and proteins cannot function o Hyperventilation too much Increase CO2 released Decrease arterial PCO2 decreased H respiratory alkalosis At …
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