GRE Subject Test: Biology : Understanding Respiratory Functions

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Respiratory Functions

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

Possible Answers:

Left atrium

Pulmonary arteries

Inferior vena cava

Superior vena cava

Right atrium

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 #22 : Animal Biology

Which statement describes the pressure in the lungs during exhalation?

Possible Answers:

Lung pressure must be equal to atmospheric pressure

Lung pressure should not change during the process

Lung pressure must be lower than atmospheric pressure

Lung pressure must be higher 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 #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 #2 : Understanding Respiratory Functions

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

Possible Answers:

Oxygen diffuses into the cell membranes of red blood cells

Oxygen is carried by white blood cells

Oxygen is carried by hemoglobin

Oxygen is free floating in the plasma of the blood

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 #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 #4 : Respiratory Physiology

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

Possible Answers:

Pressure remains constant

Pressure decreases

Pressure decreases, then increases

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 #1 : Understanding Other Respiratory Physiology

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

Possible Answers:

Decreased heart rate

Alkalosis

Auto-immune disease

Combustion

Acidosis

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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