回顧問題不定期更新 Study Questions are Made by Prof. Cruz & Prof. Moore from Oberlin College & Conservatory

Lectures 14 and 15: The Respiratory System

1. Explain “countercurrent exchange.”

2. Concurrent exchange can (and does) facilitate gas exchange, but cannot equal the level of effectiveness of countercurrent gas exchange. Explain why.

3. How does the thin film of water that coats the interior of insect tracheole tips, cells in the leaf mesophyll, and the inside surfaces of our lungs enhance gas exchange?

4. Why is airflow in the lungs of mammals, reptiles and amphibians said to be “tidal”?

5. How does the volume of the rib cage (and therefore the lungs, which are affixed to the inside of the rib cage) change during inhalation? During exhalation?

6. Explain why a bird may be described as a ‘better breather’ than, say, you. Be sure to include in your explanation the adaptations that enable birds be ‘better breathers.’

7. In bird parabronchi as well as in bird lungs, air flow is forcible and one-way. What causes the greater force with which air is flowing, and why is it one-way (not tidal)?

8. In your own words, describe the phenomenon of cooperativity to your study partner.

9. Assume there is a galaxy somewhere that has humanoids living in it. Alas, the hemoglobin of these humanoids does NOT exhibit cooperativity. Describe or plot the rate at which humanoid hemoglobin would bind O2 at different partial pressures of O2.

10. How do partial pressure of O2, [H+] of plasma, and temperature of the blood, respectively, affect the capacity of the heme groups in hemoglobin to hold onto (bind) O2? Note that [H+] means “concentration of hydrogen ions”, not pH—which means, “negative logarithm of the hydrogen-ion concentration in a solution”.

11. What is the adaptive value of the fact that fetal hemoglobin has an oxygen-dissociation curve that is ‘shifted to the left’? How about myoglobin’s curve also being ‘shifted to the left’?

12. Explain why you would want your Hb-O2 dissociation curve shifted to the right when you are running a marathon.

13. How does pCO2 affect the rate of CO2 dissolution in water? How about it affecting the rate of O2 dissolution in the same volume of water?

14. How does O2 transport in the blood differ from CO2 transport? In what ways are they similar?

15. Explain in plain English how the sigmoid nature of the O2 dissociation curve explains the supremely suitable nature of hemoglobin in transporting O2 in our bodies.

16. Using this image of the capillary bed, make a list of the different kinds of aqueous liquids that are to be found. For each of those liquids, indicate whether pO2 is greater than or less than pCO2. Assume that the cells in which the capillary bed is embedded are those of your arm muscles and you are bench-pressing 200 pounds.

17. The diffusion of gas molecules through the air contained within the tracheoles of a butterfly occurs at exactly the same rate as that in the lungs of an alligator. So why can’t (aren’t) butterflies able to attain the size of alligators?

18. Compare and contrast the following:

a) hemoglobin vs. hemolymph

b) left shift vs. right shift

c) myoglobin vs. hemoglobin

d) heme groups and non-heme binding sites in the hemoglobin molecule

e) spiracle vs. tracheole

f) pCO2 in your IF when you are resting vs. when you are competing in a bike race

19. Explain how CO2 (a toxic gas) is modified chemically to become less toxic during transport in the circulatory system. Be able to explain the importance of these proteins in this ‘detoxification’ process:

a) Na+/H+ exchanger

b) Carbonic anhydrase

c) Cl-/bicarbonate exchanger

20. What is partial pressure? Explain its role in predicting how rapidly a gas will diffuse in plasma or IF.

21. Why is it more difficult to breathe at high elevations (e.g., high mountains) than it is at sea level, even if the air in both places is 21% oxygen?

22. Hemoglobin combines with H to form Hb.H and with CO2 to form Hb.CO2. Both of these compounds are useless is respiration, simply hindering Hb from performing its job of transporting O2. How is the rate of formation of these compounds in the cytoplasm of red blood cells minimized?

BONUS Cool video: https://www.labroots.com/trending/plants-and-animals/1914/here-s-how- smaller-creatures-like-beetles-take-advantage-of-surface-tension

The captured bubble contains air and is positioned over the anal spiracle of this diving beetle. The O2 in that air diffuses into the tracheoles because pO2 favors it. CO2 from the beetle diffuses into the bubble because pCO2 favors it. When* will this beetle release its bubble, swim up to the surface, and capture another bubble? (*under what conditions of pO2 and pCO2)

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離久-張所長