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Apr 7th MondayGas Exchange- Air pressure is dependent on o T(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 isdependent 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 isa 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 bloodo For blood returning to the lungs PCO2 = 46 mm Hg, PO2 = 40 mm Hgo 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 wasteproduct 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  alveolio 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 soluble2. 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 isthe 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 13-26o 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 backto 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 relationshipo 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-) = solubleQuestion 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- Problemso Hypoventilation (too little) CO2 not releases Increased arterial PCO2 increased H+ = respiratory alkalosis Causes


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OSU EEOB 2520 - Gas Exchange

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