AP Biology : Respiratory Physiology

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #1 : Understanding Respiratory Functions

Which of the given circulatory system elements has the highest partial pressure of oxygen?

Possible Answers:

Superior vena cava

Right atrium

Left atrium

Pulmonary arteries

Inferior vena cava

Correct answer:

Left atrium

Explanation:

The left atrium receives blood from the pulmonary veins, which carry blood that was freshly oxygenated from the lungs to the heart. The partial pressure of oxygen is always highest soon after oxygenation, thus blood returning from the lungs would have a high partial pressure.

The superior and inferior vena cavae return deoxygenated blood from the body to the heart, and would have very low oxygen partial pressures. The right atrium receives this deoxygenated blood from the vena cavae and transfers it to the right ventricle. From the ventricle, the deoxygenated blood is transported to the lungs via the pulmonary arteries. It only becomes oxygenated again after reaching the lungs, and then returns to the heart through the pulmonary veins.

Example Question #2 : Understanding Respiratory Functions

Which statement describes the pressure in the lungs during exhalation?

Possible Answers:

Lung pressure should not change during the process

Lung pressure must be higher than atmospheric pressure

Lung pressure must be equal to atmospheric pressure

Lung pressure must be lower than atmospheric pressure

Correct answer:

Lung pressure must be higher than atmospheric pressure

Explanation:

This question requires a basic understanding of general chemistry and/or general physics. Remember that gas will only move from an area of high pressure to low pressure; thus, if air is moving out of the lungs, the pressure inside of the lungs must be greater than the pressure outside of the lungs. The point at which air does not move in or out of the lungs is a signal that the pressure of the gas inside of the lungs is equal to that of atmospheric pressure.

In a biological sense, remember that the diaphragm contracts to cause inhalation, which results from negative or decreased pressure in the lungs. When the diaphragm relaxes, the pressure in the lungs must increase again. The increase in pressure forces the air out of the lungs and back into the atmospheric environment.

Example Question #11 : Respiratory System

What causes air to enter human lungs?

Possible Answers:

Air diffuses into the lungs due to the decreased  content relative to the air outside our body.

Smooth muscle in the trachea guides the flow of air into the lungs.

Cillia in the trachea guide the flow of air into the lungs.

The decreased concentration of  in the lungs decreases the density of that air, and denser air outside the body "sinks" into the lungs.

The contraction of the diaphragm increases the volume of the lungs, decreasing the pressure relative to the air outside the body.

Correct answer:

The contraction of the diaphragm increases the volume of the lungs, decreasing the pressure relative to the air outside the body.

Explanation:

Increasing the volume of a container (in this case, the lungs) while keeping the contents (air molecules) the same will decrease the pressure. If no barrier is present (as when holding your breath), pressure will tend to equalize between areas of differing pressure. In order to equalize the pressure, air molecules from outside the body rush into the expanded lungs. The concentration of oxygen does not impact inhalation, and cilia are not used to inhale.

Example Question #12 : Respiratory System

To initiate inhalation, the diaphragm contracts, making the pressure inside the lungs __________.

Possible Answers:

lower than the pressure outside the body

higher than the pressure outside the body

None of these

the same as the pressure outside the body

zero

Correct answer:

lower than the pressure outside the body

Explanation:

Inhalation happens by making the pressure in the lungs lower relative to the pressure outside the body. When the diaphragm contracts, it increases the volume of the thoracic cavity. By Boyle's law, there is an inverse relationship between pressure and volume of a gas. Thus the pressure of the thoracic cavity decreases and since air will flow from high to low pressure, this pulls air into the lungs during inhalation.

Example Question #1 : Understanding Respiratory Functions

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

Possible Answers:

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

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

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

Gases move between alveoli and blood vessels via passive diffusion

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 #4 : Understanding Respiratory Functions

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

Possible Answers:

Oxygen is free floating in the plasma of the blood

Oxygen is carried by hemoglobin

Oxygen is carried by white blood cells

Oxygen diffuses into the cell membranes of red blood cells

Oxygen diffuses through all the cells in the body

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 #1 : Respiratory 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:

higher . . . lower

lower . . . higher

higher . . . equal

lower . . . equal

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 #21 : Respiratory System

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

Hyperventilating will not affect 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 an increase in the blood's pH

Hyperventilating will retain more  and result in a decrease in 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.

Example Question #6 : Understanding Respiratory Functions

What happens to the pressure of the lungs to initiate inspiration?

Possible Answers:

Pressure remains constant

Pressure decreases, then increases

Pressure decreases

Pressure increases, then decreases

 Pressure increases

Correct answer:

Pressure decreases

Explanation:

During inspiration, the lungs expand as the diaphragm contracts and internal intercostal muscles relax. As the volume of the thoracic cavity increases, its pressure decreases. This creates a pressure gradient, driving air from an area of high pressure (the environment) into the area of low pressure (the lungs).

Example Question #7 : Understanding Respiratory Functions

What phenomenon occurs in the blood when an individual holds their breath for an extended period?

Possible Answers:

Alkalosis

Auto-immune disease

Acidosis

Decreased heart rate

Combustion

Correct answer:

Acidosis

Explanation:

When you are not breathing, your respiratory system cannot perform its function. Unwanted gases, such as carbon dioxide, cannot be removed from the system and necessary gases, such as oxygen, cannot enter the system. This causes a buildup of carbon dioxide in the body, which leads to acidosis. Carbon dioxide is converted to carbonic acid via carbonic anhydrase. This carbonic acid builds in the blood, lowering its pH.

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