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Transport and exchange of O 2 and CO 2

Lungs: pH 7.4 Temp 37 ° C Tissues: pH 7.38 Temp 38 ° C. Transport and exchange of O 2 and CO 2. In the lungs: external respiration. Gas moves as a result of concentration gradient Rise in concentration of O 2 in alveolus causes diffusion of O 2 into capillary

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Transport and exchange of O 2 and CO 2

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  1. Lungs: pH 7.4 Temp 37 °C Tissues: pH 7.38 Temp 38 °C Transport and exchange of O2 and CO2

  2. In the lungs: external respiration • Gas moves as a result of concentration gradient • Rise in concentration of O2 in alveolus causes diffusion of O2 into capillary • High CO2 in capillary causes diffusion of CO2 into alveolus • Gases move from high to low concentration or high to low partial pressure • Note: before CO2 can diffuse out it must come out of solution; blood becomes less acidic in lungs

  3. In the tissues: internal respiration • O2 is low in tissues because it is used up during aerobic cellular respiration • O2 diffuses into tissues (leaving RBC's) • CO2 diffuses into capillary

  4. Blood and transporting O2(and CO2) • Most O2 is carried by hemoglobin on RBC's • Without Hb, blood would only carry 1/60th amount of O2 • O2 combines with iron portion of Hb • Hb is a quaternary structure • Each Hb molecule can carry up to 4 O2 molecules

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  7. Hb binds with O2 at high O2 pressure (lungs) Hb releases O2 at low O2 pressure (tissues) O2 binding with HB is facilitated in cooler temps and neutral pH (lungs) Release of O2 is facilitated in the tissues by warm temp and a slightly acidic pH

  8. External respiration: lungs Hb + O2 → HbO2 Reduced Hb Oxyhemoglobin (dark purple) (bright red) Internal respiration: tissue HbO2 → Hb + O2 CO (carbon monoxide) can bind with Hb irreversibly and prevents O2 from binding (called carbon monoxide poisoning)

  9. Carbon Dioxide is produced in the tissues Three ways to transport CO2 • Most CO2 combines with H2O and is transported in blood plasma, dissolved as bicarbonate ion • A small amount of CO2 is carried by Hb. This complex is called carbaminohemoglobin • About 9% of CO2 is dissolved directly into the blood

  10. Way #1 CO2 and H2O This is for internal respiration CO2 + H2O → H2CO3 → H+ + HCO3- Carbonic anhydrase speeds up the above reaction, ensuring that there is a net movement of CO2 into the blood from the tissues But H+ would change acidity, causing problems H+ help dislodge O2 so they can move into the tissues, then they attach to the Hb H+ + Hb → HHb Therefore Hb acts as a buffer

  11. Way #1 CO2 and H2O cont'd This is for external respiration At lungs H+ dislodged from Hb by O2 HHb → H+ + Hb H+ combines with HCO3- to form CO2 and H2O H+ + HCO3- → H2CO3 → CO2 + H2O Bicarbonate Carbonic acid

  12. Way # 2 CO2 carried by Hb For external respiration HbCO2 → Hb + CO2 For internal respiration Hb + CO2 → HbCO2

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