Transport & Diffusion of Gases SBI3U(G) PDF

Transport & Diffusion of Gases SBI3U(G) (Text Reference Pg. 447-449) Key Concept: Diffusion! What is diffusion??? A refresher video! Amoeba Sisters: Diffusion (7 min)  The Atmosphere Earth is surrounded by atmosphere ◦Most dense at sea level (highest pressure) ◦As altitude increases, density de...

Transport & Diffusion of Gases SBI3U(G) (Text Reference Pg. 447-449) Key Concept: Diffusion! What is diffusion??? A refresher video! Amoeba Sisters: Diffusion (7 min)  The Atmosphere Earth is surrounded by atmosphere ◦Most dense at sea level (highest pressure) ◦As altitude increases, density decreases (pressure also decreases) Atmospheric pressure is often measured in pascals (Pa) ◦Very small, therefore usually measured in kilopascals (kPa) ◦Sea level = 101.3kPa; Mount Everest = 31kPa -You may also see it measured in mmHg (millimeters mercury) Sea level - 760 mm Hg; Mount Everest = 250 mm Hg Composition of Atmospheric Air and Expired Air in a Typical Subject 78% 21% 0.04% 0.96% Po2 in cells Therefore oxygen leaves the blood and enters the body cells. Transport of Gases in the Blood 1) Oxygen How is oxygen carried in the blood? ◦Blood contains red blood cells (RBC) surrounded by fluid called plasma ◦Most oxygen (98.5%) carried by RBCs (as oxyhaemoglobin) 🡪 remaining 1.5% dissolved in plasma ◦RBCs contain hemoglobin (Hb) ◦each Hb molecule contains 4 heme groups ◦each heme group can carry one O2 molecule, therefore each Hb can carry FOUR O2 ◦Each RBC contains ~270 million Hb molecules ◦An adult has around 25 trillion RBC’s in their body Hemoglobin Hemoglobin Transport of Gases in the Blood 1) Oxygen When blood encounters oxygen depleted tissue (in the body cells)… ◦O2 in the plasma (1.5%) leaves first ◦Then O2 separates from the iron atom for two reasons: 1. There is now a reduction in Po2 in the blood plasma 2. The lower pH (acidity) near cells (see CO2 transport) ◦The newly freed oxygen molecules now move, by diffusion, from the blood through interstitial fluid and into the tissue cells 🡪 there it enters the mitochondria in the cell Transport of Gases in the Blood 2) Carbon Monoxide (CO) ◦Dangerous air contaminant because hemoglobin prefers carbon monoxide over O2. ◦It deprives body tissues of O2. ◦Is odourless and colourless, so unaware that it is being inhaled. ◦Lethal concentrations cause unconsciousness and death. Transport of Gases in the Blood 3) Carbon Dioxide (CO2) The PCO2 of interstitial tissue is 5.60 kPa, the blood PCO2 is 5.33 kPa. Thus CO2 diffuses from the cells (interstitial fluid) into the blood. PCO2 = 5.33kPa PCO2 = 5.60kPa Transport of Gases in the Blood 3) Carbon Dioxide (CO2) How is CO2 carried in the blood? ◦Some is dissolved as CO2 in the plasma (~7%) ◦Some CO2 is carried by the Hb as carbaminohemoglobin (20%) ◦Most CO2 is carried as bicarbonate ions in the blood plasma. The ionic form returns to lungs to be converted into CO2 and exhale (~73%) CO2 + H2O 🡪 H2CO3 🡪 HCO3- + H+ Carbonic acid Bicarbonate ions Transport of Gases in the Blood 3) Carbon Dioxide (CO2) How is CO2 carried in the blood? ome is dissolved in the plasma (~7%) some CO2 is carried by the Hb as carbaminohemoblobin (20%) H+ createsions Most CO2 is carried as bicarbonate an acidic in the blood plasma. The ionic form returns to lungsenvironment. to How? be Must get rid of it. converted into CO2 and exhale (~70%) CO2 + H2O 🡪 H2CO3 🡪 HCO3- + H+ Carbonic acid Bicarbonate ions How Red Blood Cell Carry Oxygen and Carbon Dioxide, Animation Transportation of Gases | Don't Memorise The Effect of Altitude on Respiration The concentration of O2 does not change depending on altitude (always 20.9%), however the density and pressure is lower at higher altitudes. The Effect of Altitude on Respiration The pressure gradient between PO2 in the air and the PO2 of the blood is reduced 🡪 rate of diffusion decreases This results in altitude sickness ◦ Shortness of breath ◦ Headache ◦ Dizziness & nausea ◦ Tiredness Effects of Hypoxia on the Brain (4 min46 s) Oxygen Dissociation Curve Oxygen Dissociation Curve -Sample Question The air we breathe is approximately 21% oxygen, 78% nitrogen and 1% argon and other gases. a) If the atmospheric pressure is 500 mmHg (the atmospheric pressure found at about halfway up Mount Everest (4350 m)), what is the partial pressure of oxygen at this altitude? Answer: Partial Pressure of gas = Atmospheric pressure X percentage of gas (O2) = 500 mmHg X 0.21 = 105 mm Hg Therefore the partial pressure of oxygen at that altitude is 105 mmHg.  Based on your previous answer (partial pressure of oxygen at 4350 m altitude is 105 mmHg), using the oxygen dissociation curve graph, determine the percentage saturation of your blood at this atmospheric level. Answer: 100% How low is too low? Review!!! Respiratory System, Part 2: Crash Course (10 min) Homework -Oxygen Dissociation Curve Assignment - Read pages 447-449 Answer p 451#1,3,4 Extension: Oxygen Dissociation Curve: Mother and Fetus Which hemoglobin is more effective at absorbing oxygen? What adaptive advantage is provided by hemoglobin that allows it to combine readily with oxygen? (each molecule can hold 4 O2 molecules so it is efficient, blood cells don’t have nuclei so can hold more hemoglobin, each time an O2 molecule binds to a part of the hemoglobin, the Hb changes its shape making it easier for more oxygen molecules to bind to it. Oxygen Dissociation Curve: Mother and Fetus Is there a significance to the difference in curve at lower O2 saturation levels? *Think of how a fetus gets its oxygen? ***The fetus gets it’s oxygen from the mother’s blood circulating through the placenta. When the mother’s blood is lower in oxygen (as some has been used for her own tissues), the fetus will be more efficient at extracting the oxygen that it needs.