AP Biology : Understanding Gas Exchange

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #81 : Systems Physiology

Choose the incorrect statement regarding gas exchange in the alveoli of the lungs.

Possible Answers:

Gases move between alveoli and blood vessels via passive diffusion

The partial pressure of carbon dioxide is lower in the systemic arteries than it is in the body tissues

The partial pressure of oxygen is lower in systemic arteries than in systemic veins

In the lungs, oxygen diffuses from the alveoli into the blood vessels

Carbon dioxide diffuses from the blood vessels into the alveoli for expiration

Correct answer:

The partial pressure of oxygen is lower in systemic arteries than in systemic veins

Explanation:

We know that systemic arteries carry oxygenated blood away from the heart and that these vessels pass through tissues, allowing oxygen to diffuse into the tissues and carbon dioxide to diffuse out into the bloodstream. We also know that veins carry blood back to the heart, which by this time is oxygen-poor due to its gas exchange with the tissues of the body. The partial pressure of oxygen in veins must be lower than it is in arteries, since the veins carry deoxygenated blood.

The remaining statements regarding gas exchange are true.

Example Question #82 : Systems Physiology

How is oxygen carried after entering the blood of the pulmonary capillaries?

Possible Answers:

Oxygen is carried by white blood cells

Oxygen is carried by hemoglobin

Oxygen diffuses through all the cells in the body

Oxygen is free floating in the plasma of the blood

Oxygen diffuses into the cell membranes of red blood cells

Correct answer:

Oxygen is carried by hemoglobin

Explanation:

Hemoglobin is the main oxygen carrier in the human body. Each hemoglobin protein is able to carry four oxygen molecules. As the hemoglobin travels through the blood vessels of the body, the oxygen is released to tissues and used in the electron transport chain.

If oxygen is unable to bind to hemoglobin, our bodies cannot carry the needed oxygen to the tissues of the body. This can occur when carbon monoxide displaces oxygen from hemoglobin.

Example Question #83 : Systems Physiology

Gases diffuse down their concentration gradients, so in order for the body to exchange respiratory gases with the air as needed, air breathed into the lungs must have a __________ concentration of oxygen and a(n) __________ concentration of carbon dioxide compared to the blood in the lungs.

Possible Answers:

lower . . . higher

lower . . . equal

higher . . . equal

higher . . . lower

Correct answer:

higher . . . lower

Explanation:

Oxygen is taken up from the blood by all cells to be used in ATP production. The process of cellular respiration (energy production) creates carbon dioxide as a waste product, which, if accumulated, can cause the blood to become dangerously acidic. Gases in the lungs diffuse passively into or out of the air entirely based on where the concentration is lowest. Thus, oxygen levels in the blood must be lower in concentration than those in the lungs in order for oxygen to enter the blood, and carbon dioxide levels in the blood must be higher than those in the lungs order for carbon dioxide to exit.

Example Question #1 : Understanding Gas Exchange

Mountain climbing at a high altitude can have an affect on one's ability to breath efficiently. At high altitudes, atmospheric pressure can decrease dramatically and result in a lower drive for oxygen into the lungs. The body will try to compensate by increasing the rate of respiration.

How does hyperventilating change the blood chemistry in the human body?

Possible Answers:

Hyperventilating will retain more  and result in a decrease in the blood's pH

Hyperventilating will release more  and result in an increase in the blood's pH

Hyperventilating will retain more  and result in an increase in the blood's pH

Hyperventilating will release more  and result in a drop in the blood's pH

Hyperventilating will not affect the blood's pH.

Correct answer:

Hyperventilating will release more  and result in an increase in the blood's pH

Explanation:

Hyperventilation will result in the expiration of more . It can be deduced that a greater amount of expired  will cause the above equation to shift to the left. The shifting of the equation to the left will further promote the conversion of  and  to  and .  Since the body uses  as a buffer, there will be a greater quantity of the bicarbonate in the body than . When the equation shifts to the left, the  will deplete at a faster rate and result in a higher  to  ratio. A higher  to  ratio will cause the body's blood to become more basic (increase in pH); therefore, hyperventilation increases blood bascicity.

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