1. 8.3 – Gas Exchange Ms. Lowrie Advanced Biology 11

2. Dalton’s Law  Dalton’s law of partial pressure:  Huh??? pressure of mixture of nonreactive gases = sum of partial pressures of individual gases

3. Dalton’s Law (revised)  Partial pressure Pressure each gas, in a mixture, exerts  Gases diffuse from high (partial) pressure to low (partial) pressure

4. Oxygen vs. Carbon Dioxide  Partial pressure of O 2 = P O 2 Highest in atmosphere Lowest in veins & tissues  Partial pressure of CO 2 = P CO 2 Highest in veins & tissues Lowest in atmosphere

6. How does it occur?  Using facilitated diffusion (technically) No energy required Faster than diffusion

7. Oxygen Transport  Moves from alveoli to blood  Transported on hemoglobin Oxyhemoglobin  In capillaries partial pressure drops O 2 detaches  Moves to cells

8. Task  Practice Questions: # 2, 3 (pg 292)  Section Questions: # 1, 4 (pg 294)  Read pg 292/293 (at least twice!)

9. Carbon Dioxide Transport  Moves from cells to blood After cellular respiration  9% carried in plasma  27% transported on hemoglobin Carbaminohemoglobin

10. Carbon Dioxide Transport

11.  64% combines with water = Carbonic acid (H 2 CO 3 ) Keeps low P CO 2 Uses enzyme (carbonic anhydrase) Figure 3(a) CO 2 + H 2 O  H 2 CO 3

12. CO 2 in Cells  Figure 4 (pg 293)

13. Carbon Dioxide Transport Carbonic Acid (H 2 CO 3 )  Spilts into bicarbonate ions (HCO 3 ¯ ) & hydrogen (H + ) Figure 3(b) H 2 CO 3  H + + HCO 3 -

14. Carbon Dioxide Transport  H + combines with hemoglobin Buffer O 2 released (to body cells)  In lungs: O 2 causes H + to break away from hemoglobin Buffer: - substance that neutralizes acids/bases - maintains original pH

15. Carbon Dioxide Transport  In lungs: Figure 3(c) CO 2 diffuses into alveoli H + + HCO 3 -  H 2 O + CO 2

16. Task  Section Questions: # 2, 3 (pg 294)

17. Breathing Rate  Controlled by brain Medulla oblongata in brain stem  Chemoreceptors Gather information about concentration of gases in blood  “chemo” = chemical (i.e. O 2 and CO 2 )

18. The Main Receptor  Carbon dioxide chemoreceptors Most sensitive Main regulators Respond to high CO 2 concentrations in blood

19. Why Not O 2 Receptors?!  Oxygen chemoreceptors: Less sensitive A backup regulator Respond to low O 2 concentrations in blood  Normal CO 2

20. O 2 Receptors Used…  Carbon monoxide (CO) poisoning: CO Binds to hemoglobin before O 2 Less O 2  Not higher CO 2  High altitudes: Thin air = less O 2  Not higher CO 2

21. Regulating Breathing 1.CO 2 builds up in blood Creates an acid  Problem: The body needs O 2 ! 2.CO 2 chemoreceptors are activated -Send messages to diaphragm and intercostal muscles 3.Breathing rate increases

22. Regulating Breathing 4.Concentration of CO 2 in blood falls 5.CO 2 chemoreceptors become inactive 6.Breathing rate returns to normal 7.System turns off

23. Negative Feedback Loop intercostal

24. Task  Section Questions: # 5, 6 (pg 294)