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Transcript
Respiration: Part 3 How does gas exchange happen? Substances diffuse from high concentrations to low concentrations Example: Scent molecules move across a room How does gas move into / out of the blood? In the lungs: O2 moves from HIGH concentration in the alveoli to LOW concentration in the blood CO2 moves from HIGH concentration in the blood to LOW concentration in the alveoli External Respiration Remember, this is the exchange between gases in the AIR and the BLOOD It takes place in the lungs through alveoli and capillary walls (each only one cell thick!) How do you diffuse the most O2 into the blood? Lung Capillary Alveolus Hemoglobin O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 = O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 HIGH Concentration LOW Concentration What just happened? Breathe in and there is more O2 in the alveoli than in the blood O2 moves from HIGH to LOW concentration Alveoli and blood are at the same concentration Hemoglobin took up four more O2 Alveoli had more O2 than the blood again O2 moves from HIGH to LOW concentration Result: We get MORE oxygen diffusing into the blood! Helpful Hemoglobin! Hemoglobin contains iron There are 200 million per red blood cell O2 4 O2 molecules can attach to each Hb molecule O2 Increases carrying capacity of O2 by 60 times Internal Respiration Exchange of O2 and CO2 between the BLOOD and the TISSUES Cells have a LOW concentration of O2 Blood has a HIGH concentration of O2 How does the O2 get from the blood to the cells? Body Cell Body Capillary Hemoglobin O2 O2 O2 O2 O2 LOW Concentration = O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 HIGH Concentration What happened this time? Blood arrives with a HIGH concentration of O2 Cells have a LOW concentration of O2 O2 diffuses out of the blood into the cells (HIGH LOW) Hb gives up its four O2 There is more O2 in the blood again More O2 diffuses out of the blood into the cells Result: We get MORE oxygen diffusing into the cells! O2 Consider this reaction: Hb + O2 (hemoglobin + O2) O2 HbO2 (oxyhemoglobin) Why will this help you to diffuse more oxygen into the blood? When there is lots of O2 the reaction shifts this way: Hb + O2 HbO2 Happens in LUNGS When there is lots of HbO2 the reaction shifts this way: Hb + O2 HbO2 Happens in TISSUES How do we maximize the transfer of O2 using Hb? Effect of temperature: Hb gives up O2 better at higher temperatures Hb attaches to O2 better at lower temperatures Effect of pH: At higher or neutral pH, Hb attaches to O2 better At lower pH, Hb gives up O2 better What are the best conditions? For TAKING UP O2? pH = High pH (Basic) Temperature = Low Temperature (Cool) Lungs This occurs in the _________________. For GIVING AWAY O2? pH = Low pH (Acid) Temperature = High Temperature (Hot) Tissues This occurs in the _________________. What happens with CO2? CO2 also diffuses from HIGH to LOW concentration In the lungs: Blood is HIGH in CO2 Alveolus is LOW in CO2 In the tissues: Cells are HIGH in CO2 Blood is LOW in CO2 Some CO2 changes into carbonic acid (H2CO3) in the blood This lets more CO2 diffuse in from the cells ALVEOLAR SPACE IN LUNG CO2 CO2 produced INTERSTITIAL FLUID CO2 CO2 BLOOD PLASMA WITHIN CAPILLARY CO2 Capillary wall CO2 CO2 CO2 H2O H2O RED BLOOD CELL Hemoglobin picks up CO2 and H+ H2CO3 HCO3– HCO3– + H+ Hemoglobin releases CO2 and H+ H2CO3 HCO3– HCO3– + H+ Why is carbon monoxide poisonous? CO + Hb HbCO Carbon monoxide + hemoglobin carboxyhemoglobin Hb has an affinity for carbon monoxide 230 times greater than its affinity for O2 Hemoglobin can’t carry oxygen because it is taken up with carbon monoxide