Question 1

Most of the carbon dioxide produced by humans is ________.

Accepted Answer

Most of the carbon dioxide produced by humans is converted to bicarbonate ions in the blood. This process involves the enzyme carbonic anhydrase, which facilitates the conversion of CO2 and water into carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions.

Question 2

What would be the consequence if we were to reverse the direction of water flow over the gills of a fish, moving water inward past the operculum, past the gills, then out the mouth? This reversal of water flow would ________.

Accepted Answer

Reversing the direction of water flow over the gills would reduce the efficiency of gas exchange because it would not allow for the efficient removal of carbon dioxide and uptake of oxygen. The normal flow of water over the gills allows for a concentration gradient to be created in which oxygen can diffuse from the water into the blood of the fish while carbon dioxide can diffuse out. Reversing the direction of water flow would disrupt this gradient and decrease the efficiency of gas exchange. Choice B is incorrect because the direction of gas exchange would remain the same. Choice C is incorrect because the efficiency of gas exchange would actually decrease.

Question 3

How has the avian lung adapted to the metabolic demands of flight?

Accepted Answer

The avian lung has a unique structure that allows for continuous airflow and gas exchange during both inhalation and exhalation, which is crucial for meeting the high metabolic demands of flight.

Question 4

Hyperventilation (rapid inhalation and exhalation) can result in respiratory alkalosis (increased blood pH). Why?

Accepted Answer

Hyperventilation causes the depletion of carbon dioxide in the blood, leading to an increase in blood pH. Carbon dioxide reacts with water in the blood to form carbonic acid, which dissociates to release hydrogen ions, thereby reducing the pH of the blood. When there is a decrease in carbon dioxide due to hyperventilation, the equilibrium shifts towards the side of carbonic acid formation, resulting in an increased pH.

Question 5

The sun shining on a tidal pool during a hot day heats the water, causing some water to evaporate. Because the water has become warmer and saltier, ________.

Accepted Answer

As water temperature and salinity increase, the solubility of gases such as oxygen decreases. This means that less oxygen will be present in the warmer, saltier water, making it more difficult for aerobic organisms to survive.

Question 6

Which of the following events would you predict as carbon dioxide is released from your muscles into the surrounding capillary bed?

Accepted Answer

The release of carbon dioxide from muscles leads to a decrease in blood pH, which enhances oxygen delivery to muscles through the Bohr effect, where hemoglobin releases more oxygen in response to lower pH.

Question 7

An oil-water mixture works as an insecticidal spray against mosquitoes and other insects because it ________.

Accepted Answer

The oil-water mixture blocks the openings into the tracheal system of the insects, inhibiting respiration and leading to their death.

Question 8

Which of the following represents the correct flow of air into the lung of a mammal?

Accepted Answer

The correct flow of air into the lung of a mammal is: larynx → trachea → bronchi → bronchioles → alveoli. The air enters through the larynx, then passes through the trachea, which branches into the two bronchi, one leading to each lung. The bronchi then divide into smaller and smaller branches called bronchioles, which finally lead to the true respiratory units of the lung, the alveoli.

Question 9

A decrease of blood pH from 7.4 to 7.2 causes hemoglobin to ________.

Accepted Answer

A decrease in blood pH from 7.4 to 7.2 indicates an increase in acidity (more H⁺ ions) that can cause hemoglobin to unload more oxygen molecules to the tissues and organs that need more oxygen. This shift in oxygen binding affinity of hemoglobin is known as the Bohr effect. As a result, hemoglobin gives up more of its oxygen molecules to counteract the effects of acidosis. Thus, the correct choice is D.

Question 10

Atmospheric pressure at the summit of Mount Everest is about one third the pressure at sea level, which is 760 mm Hg. If oxygen makes up 21% of the atmosphere by volume, the partial pressure of oxygen (PO₂) on Mount Everest is approximately ________.

Accepted Answer

The atmospheric pressure at the summit of Mount Everest is about one third of 760 mm Hg, which is approximately 253 mm Hg. Since oxygen makes up 21% of the atmosphere, the partial pressure of oxygen is 0.21 * 253 mm Hg ≈ 53 mm Hg.

Question 11

Consider the following reaction. If the pH of the blood was decreased, then the ________.
CO₂ + H₂O↔H₂CO₃↔HCO₃⁻ + H⁺

Accepted Answer

A decrease in pH indicates an increase in H⁺ concentration, which shifts the equilibrium to the left, increasing CO₂.

Question 12

Compared to mammals that are not adapted for diving, diving mammals ________.

Accepted Answer

Diving mammals can store more oxygen in their muscles due to higher concentrations of myoglobin, which allows them to sustain longer dives.

Question 13

A person with a tidal volume of 450 mL (milliliters), a vital capacity of 4000 mL, and a residual volume of 1000 mL would have a potential total lung capacity of ________.

Accepted Answer

The total lung capacity is the sum of the vital capacity and the residual volume, so the potential total lung capacity would be:
4000 mL (vital capacity) + 1000 mL (residual volume) = 5000 mL.

Question 14

During most daily activities, the human respiration rate is most closely linked to the blood levels of ________.

Accepted Answer

The human respiration rate is regulated by the level of carbon dioxide in the bloodstream. When carbon dioxide levels rise, the body increases its respiration rate in order to expel the excess carbon dioxide and maintain appropriate oxygen and pH levels in the blood.

Question 15

Based on the graph, which of the following statements is correct?

Accepted Answer

The answer of Based on the graph, which of the...

Question 16

Under identical atmospheric conditions, freshwater ________.

Accepted Answer

Freshwater has greater solubility for oxygen than seawater due to its lower salinity and lower temperature.

Question 17

Carbon dioxide levels in the blood and cerebrospinal fluid affect pH. This enables the organism to sense a disturbance in gas levels as ________.

Accepted Answer

The medulla oblongata, which is in contact with cerebrospinal fluid, monitors pH and uses this measure to control breathing. This is known as the respiratory control center. When CO2 levels rise and pH decreases, the medulla oblongata sends signals to increase breathing rate to remove excess CO2 and bring pH levels back to normal.

Question 18

A rabbit taken from a meadow near sea level and moved to a meadow high on a mountainside would have some trouble breathing. Why?

Accepted Answer

The partial pressure of oxygen is lower at high elevations, making it harder for the rabbit to obtain the oxygen it needs for respiration.

Question 19

Some human infants, especially those born prematurely, suffer serious respiratory failure because of ________.

Accepted Answer

Premature infants may not have fully developed lungs and may lack adequate amounts of surfactant, a molecule that helps prevent lung collapse. This can lead to serious respiratory failure, and is a common problem in premature babies. Option A is partially correct but doesn't explain the specific cause of respiratory failure. Option B is incorrect, as overproduction of surfactants is not a known cause of respiratory failure. Option D is also incorrect, as while mutations in genes related to lung formation can cause respiratory problems, it is not specified as a cause of respiratory failure in premature infants in this context.

Question 20

During aerobic exercise, the partial pressure of oxygen in muscle cells will ________, thus the rate of diffusion of oxygen into the muscle tissue from the blood will ________.

Accepted Answer

During aerobic exercise, the partial pressure of oxygen in muscle cells decreases because oxygen is being consumed for energy production. This decrease in partial pressure creates a larger gradient between the oxygen in the blood and the oxygen in the muscle cells, thus increasing the rate of diffusion of oxygen into the muscle tissue.

Quiz 42: Circulation and Gas Exchange