1. Transport and exchange of O 2 and CO 2 Lungs:pH 7.4Temp 37 °C Tissues:pH 7.38Temp 38 °C

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 High CO 2 in capillary causes diffusion of CO 2 into alveolus Gases move from high to low concentration or high to low partial pressure Note: before CO 2 can diffuse out it must come out of solution; blood becomes less acidic in lungs

3. In the tissues: internal respiration O 2 is low in tissues because it is used up during aerobic cellular respiration O 2 diffuses into tissues (leaving RBC's) CO 2 diffuses into capillary

4. Blood and transporting O 2 (and CO 2 ) Most O 2 is carried by hemoglobin on RBC's Without Hb, blood would only carry 1/60 th amount of O 2 O 2 combines with iron portion of Hb Hb is a quaternary structure Each Hb molecule can carry up to 4 O 2 molecules

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8. Hb binds with O 2 at high O 2 pressure (lungs) Hb releases O 2 at low O 2 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

9. External respiration: lungs Hb + O 2 → HbO 2 Reduced HbOxyhemoglobin (dark purple) (bright red) Internal respiration: tissue HbO 2 → Hb + O 2 CO (carbon monoxide) can bind with Hb irreversibly and prevents O 2 from binding (called carbon monoxide poisoning)

10. Carbon Dioxide is produced in the tissues Three ways to transport CO 2 1.Most CO 2 combines with H 2 O and is transported in blood plasma, dissolved as bicarbonate ion 2.A small amount of CO 2 is carried by Hb. This complex is called carbaminohemoglobin 3.About 9% of CO 2 is dissolved directly into the blood

11. Way #1 CO 2 and H 2 O This is for internal respiration CO 2 + H 2 O → H 2 CO 3 → H + + HCO 3 - Carbonic anhydrase speeds up the above reaction, ensuring that there is a net movement of CO 2 into the blood from the tissues But H + would change acidity, causing problems H + help dislodge O 2 so they can move into the tissues, then they attach to the Hb H + + Hb → HHb Therefore Hb acts as a buffer

12. Way #1 CO 2 and H 2 O cont'd This is for external respiration At lungs H + dislodged from Hb by O 2 HHb → H + + Hb H + combines with HCO 3 - to form CO 2 and H 2 O H + + HCO 3 - → H 2 CO 3 → CO 2 + H 2 O Bicarbonate Carbonic acid

13. Way # 2 CO 2 carried by Hb For external respiration HbCO 2 → Hb + CO 2 For internal respiration Hb + CO 2 → HbCO 2