Respiration - Video Tutorials & Practice Problems
Respiration
When determining the directions that molecules will move in external and internal respiration:
Molecules will always move down the pressure gradient according to their individual partial pressures.
Molecules will move up the pressure gradient for internal respiration and down the pressure gradient for external respiration.
CO2 will always move up the pressure gradient, while O2 will always move down the pressure gradient.
Molecules will always move from the area of greatest total pressure to the area of lowest total pressure.
Internal and External Respiration
Respiration Example 1
What is the approximate partial pressure of oxygen in the blood as it enters and leaves the capillaries of the alveoli?
Enters: 40 mm Hg, Leaves: 46 mm Hg.
Enters: 46 mm Hg, Leaves: 40 mm Hg.
Enters: 100 mm Hg, Leaves: 46 mm Hg.
Enters: 40 mm Hg, Leaves: 100 mm Hg.
What is one difference between air in the alveoli compared to air in the atmosphere?
The total pressure of air in the alveoli will be greater than the total pressure of air in the atmosphere.
The partial pressure due to water vapor is much greater in the alveoli than in the atmosphere.
The partial pressure due to carbon dioxide is greater in the atmosphere than in the alveoli.
The partial pressure of oxygen is equal to the partial pressure of carbon dioxide in the alveoli, but not in the atmosphere.
External Respiration
Respiration Example 2
Which gradient most directly determines the direction that oxygen and carbon dioxide molecules will move between the air in the alveoli and the blood:
The pressure gradient between alveolar air and the blood plasma.
The concentration gradient between the hemoglobin and the blood plasma.
The concentration gradient between carbon dioxide and oxygen.
The pressure gradient between the hemoglobin and alveolar air.
Choose which of the following statements is correct.
The pressure gradient for O2 is much less than the pressure gradient for CO2, but because of hemoglobin, more O2 can be carried in the blood.
Because the pressure gradient for O2 is greater than the pressure gradient for CO2, more molecules of O2 will be exchanged in the alveoli than molecules of CO2.
Most molecules of O2 are carried by hemoglobin, but it is the gradient between the plasma and the alveoli that determines the movement of O2 in and out of the blood.
O2 is 20 times more soluble than CO2, meaning that much more O2 can be carried in the blood plasma than CO2.
Internal Respiration
Respiration Example 3
For internal respiration, which of the following must be true:
I. The total amount of CO2 exchanged equals the amount of O2 exchanged.
II. Carbon dioxide will move down its concentration gradient to enter the blood.
III. The partial pressure of O2 in the tissue before gas exchange is ≥ 40 mm Hg.
I only.
I and II.
III only.
I, II, and III are true.
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