Biology, Eighth Edition (Raven)

Chapter 49: The Circulatory and Respiratory Systems

Gas Exchange During Respiration

Why are red blood cells needed to transport gases in the blood? Oxygen and carbon dioxide will both go into solution in the plasma (the fluid part of the blood). Hemoglobin in red blood cells will bond to both oxygen and carbon dioxide. There are several reasons why red blood cells are necessary for respiration. First oxygen gas has a very low solubility in blood fluids and the circulatory system would not be able to deliver enough oxygen to tissues using dissolved oxygen alone. Second, hemoglobin takes gases out of solution which maintains a concentration gradient and continued diffusion of gases into the blood. Third carbon dioxide in solution reduces the pH of the blood with harmful effects.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

The direction of gas movement is determined by
A)temperature.
B)size of the gas molecule.
C)solubility of the gas in blood.
D)partial pressure differences.
E)pH.
2.

Which of the following statements about partial pressures of gases is TRUE?
A)PO2 in lung is greater than PO2 in blood ; PCO2 in lung is greater than PCO2 in blood
B)PO2 in lung is greater than PO2 in blood ; PCO2 in lung is less than PCO2 in blood
C)PO2 in lung is greater than PO2 in blood ; PCO2 in lung = PCO2 in blood
D)PO2 in lung is less than PO2 in blood ; PCO2 in lung is less than PCO2 in blood
E)PO2 in lung is less than PO2 in blood ; PCO2 in lung is greater than PCO2 in blood
3.

Which of the following statements about partial pressures of gases is TRUE?
A)PO2 in blood is greater than PO2 in tissues ; PCO2 in blood is greater than PCO2 in tissues
B)PO2 in blood is greater than PO2 in tissues ; PCO2 in blood is less than PCO2 in tissues
C)PO2 in blood is greater than PO2 in tissues ; PCO2 in blood = PCO2 in tissues
D)PO2 in blood is less than PO2 in tissues ; PCO2 in blood is less than PCO2 in tissues
E)PO2 in blood is less than PO2 in tissues ; PCO2 in blood is greater than PCO2 in tissues
4.

Oxygen-rich blood is carried through pulmonary arteries from the lungs to the heart.
A)True
B)False
5.

Oxygen-poor blood is carried through systemic veins from the body tissues back to the heart.
A)True
B)False
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