Chapter 18 concept questions Flashcards
Cellular metabolism review: which of the following three metabolic pathways—glycolysis, the citric acid cycle, and the electron transport system—is directly associated with (a) O2 consumption and with (b) CO2 production?
(a) electron transport system, (b) citric acid cycle
Why doesn’t the movement of oxygen from the alveoli to the plasma decrease the PO2 of the alveoli?
The PO2 of the alveoli is constantly being replenished by fresh air. [p.553]
If nitrogen is 78% of atmospheric air, what is the partial pressure of this gas when the dry atmospheric pressure is 720 mm Hg?
720 mm Hg x 0.78 N2 = 561.6 mm Hg
At the summit of Mt. Everest, an altitude of 8850 m, atmospheric pressure is only 250 mm Hg. What is the PO2 of dry atmospheric air atop Everest? If water vapor added to inhaled air at the summit has a partial pressure of 47 mm Hg, what is the PO2 of the inhaled air when it reaches the alveoli?
Why would left ventricular failure or mitral valve dysfunction cause elevated pulmonary blood pressure?
Blood pools in the lungs because the left heart is unable to pump all the blood coming into it from the lungs. Increased blood volume in the lungs increases pulmonary blood pressure.
If alveolar ventilation increases, what happens to arterial PO2? To arterial PCO2? To venous and PO2?Explain your answers.
When alveolar ventilation increases, arterial PO2 increases because more fresh air enters the alveoli. Arterial PCO2 decreases because the low of fresh air dilutes alveolar PCO2. The CO2 pressure gradient between venous blood and the alveoli increases, causing more CO2 to leave the blood. Venous PO2 and PCO2 do not change because they are determined by metabolism in the cells.
True or false? Plasma with a PO2 of 40 mm Hg and a PCO2 of 40 mm Hg has the same concentrations of oxygen and carbon dioxide.
False. Plasma is essentially water, and Fig. 18.4 shows that CO2 is more soluble in water than O2.
A saline solution is exposed to a mixture of nitrogen gas and hydrogen gas in which PH2 = PN2. What information do you need to predict whether equal amounts of H2 and N2 dissolve in the solution?
You need to know the solubility of each gas in that solution.
Can a person breathing 100% oxygen at sea level achieve 100% saturation of her hemoglobin?
Yes. Hemoglobin reaches 100% saturation at 650 mm Hg. If Patm = 760 mm Hg and the atmosphere is 100% oxygen, then PO2 is 760 mm Hg.
What effect does hyperventilation have on the percent saturation of arterial hemoglobin?
The flatness at the top of the PO2 curve tells you that hyperventilation causes only a minimal increase in the percent saturation of arterial Hb.
A muscle that is actively contracting may have a cellular PO2 of 25 mm Hg. What happens to oxygen binding to hemoglobin at this low PO2? What is the PO2 of the venous blood leaving the active muscle?
As the PO2 falls, more oxygen is released. The PO2 of venous blood leaving the muscle is 25 mm Hg, the same as the PO2 of the muscle.
How would an obstruction of the airways affect alveolar ventilation, arterial PCO2 and the body’s pH?
An airway obstruction would decrease alveolar ventilation and increase arterial PCO2. Elevated arterial PCO2 would increase arterial H+ and decrease pH.
