Deck 49: Gas Exchange in Animals

Question 1

An elephant uses its trunk

A) to pluck leaves from trees.
B) to pull plants from the ground.
C) to obtain water to squirt in its mouth.
D) as a snorkel.
E) All of the above

Answer 1

E

Question 2

Breathing provides the body with the oxygen required to support the energy metabolism of all cells and also eliminates _______, one of the waste products of cell metabolism.

A) carbon dioxide
B) carbon monoxide
C) carbon tetrachloride
D) calcium carbonate
E) carbonic acid

Answer 2

A

Question 3

Myoglobin

A) binds O₂ at P_O2 values at which hemoglobin is releasing its bound O₂.
B) has a lower affinity for O₂ than hemoglobin does.
C) consists of four polypeptide chains, just as hemoglobin does.
D) provides an immediate source of O₂ for muscle cells at the onset of activity.
E) can bind four O₂ molecules at once.

Answer 3

A

Question 4

The rate at which a gas diffuses between two locations is _______ the distance between those locations.

A) unrelated to
B) positively related to
C) the square root of
D) negatively related to
E) None of the above

Question 5

The hemoglobin of a human fetus

A) is the same as that of an adult.
B) has a higher affinity for O₂ than adult hemoglobin has.
C) has only two protein subunits instead of four.
D) is supplied by the mother's red blood cells.
E) has a higher affinity for BPG than adult hemoglobin has.

Question 6

Which of the following statements is not true?

A) Respiratory gases are exchanged only by diffusion.
B) O₂ has a lower rate of diffusion in water than in air.
C) The O₂ content of water falls as the temperature of water rises.
D) The amount of O₂ in the atmosphere decreases with increasing altitude.
E) Birds have evolved active transport mechanisms to augment their respiratory gas exchange.

Question 7

Humans have difficulty breathing at high elevations because _______ than at low elevations.

A) O₂ makes up a lower percentage of the air
B) the temperature is lower
C) the barometric pressure is higher
D) the partial pressure of O₂ is lower
E) the air is drier

Question 8

The amount of O₂ carried by hemoglobin depends on the P_O2 in the blood. Hemoglobin in active muscles

A) becomes saturated with O₂.
B) takes up only a small amount of O₂.
C) readily unloads O₂.
D) tends to decrease the P_O2 in the muscle tissues.
E) is denatured.

Question 9

When the level of CO₂ in the bloodstream increases,

A) the rate of respiration decreases.
B) the pH of the blood rises.
C) the respiratory centers become dormant.
D) the rate of respiration increases.
E) the blood becomes more alkaline.

Question 10

When elephants are swimming, what protects the blood vessels around their lungs from water pressure damage?

A) They swim only in shallow water.
B) Their lungs are attached to the chest cavity with dense connective tissue.
C) They hold their breath.
D) They have thick-walled blood vessels near their lungs.
E) Their ribs, which surround all their blood vessels, provide protection and support.

Question 11

In the human gas exchange system,

A) the lungs and airways are completely collapsed after a forceful exhalation.
B) the average P_O2 concentration of air inside the lungs is always lower than that in the air outside the lungs.
C) the P_O2 of the blood leaving the lungs is greater than that of the exhaled air.
D) the amount of air that is moved per breath during normal, at-rest breathing is termed the total lung capacity.
E) O₂ and CO₂ are actively transported across the alveolar and capillary membranes.

Question 12

Which statement about the human gas exchange system is not true?

A) During inhalation, a negative pressure exists in the space between the lung and the thoracic wall.
B) Smoking one cigarette can immobilize the cilia lining the airways for hours.
C) The respiratory control center in the medulla responds more strongly to changes in arterial O₂ concentration than to changes in arterial CO₂ concentration.
D) Without surfactant, the work of breathing is greatly increased.
E) The diaphragm contracts during inhalation and relaxes during exhalation.

Question 13

Which statement about the gas exchange system of birds is not true?

A) Respiratory gases are not exchanged in the air sacs.
B) A bird can achieve more complete exchange of O₂ from air to blood than humans can.
C) Air passes through birds' lungs in only one direction.
D) The gas exchange surfaces in bird lungs are the alveoli.
E) A breath of air remains in the system for two breathing cycles.

Question 14

Most CO₂ in the blood is carried

A) in the cytoplasm of red blood cells.
B) as CO₂ dissolved in the plasma.
C) in the plasma as bicarbonate ions.
D) bound to plasma proteins.
E) in red blood cells bound to hemoglobin.

Question 15

Small insects may take a bubble of air underwater when they dive. The bubble can serve as an air tank for some time because

A) as CO₂ increases, the bubble inflates.
B) as O₂ is consumed, air pressure in the bubble decreases.
C) as O₂ is consumed, more O₂ diffuses into the bubble.
D) the partial pressure of nitrogen remains constant.
E) for each O₂ molecule used, a CO₂ molecule replaces it.

Question 16

Which statement about gas exchange in fish is true?

A) Blood flows over the gas exchange surfaces in a direction opposite to the flow of water.
B) Gases are exchanged across the gill arches.
C) Ventilation of the gills is tidal in fast-swimming fishes.
D) Less work is needed to ventilate gills in warm water than in cold water.
E) The path length for diffusion of respiratory gases is determined by the length of the gill filaments.

Question 17

Oxygen can be exchanged more easily in air than in water because

A) the oxygen content of air is higher than that of water.
B) oxygen diffuses more slowly in water than in air.
C) more energy is required to move water than air because water is denser.
D) Both a and b
E) All of the above

Question 18

At sea level, atmospheric pressure is about _______ mm mercury.

A) 454
B) 1,000
C) 760
D) 940
E) 1

Question 19

Gas exchange in animals always involves

A) cellular respiration.
B) breathing movements.
C) neural control.
D) diffusion between internal body fluids and the outside medium.
E) active transport of gases.

Question 20

A key problem faced by elephants when they are swimming is

A) the pressure difference between their blood vessels and the water.
B) water entering their cells and causing lysis.
C) water leaving their cells in response to a concentration gradient.
D) infection by pathogens.
E) None of the above

Question 21

In the respiratory cycle of birds, air flows through the trachea, to the bronchi, and then

A) into the parabronchi.
B) back through the trachea.
C) to the air capillaries.
D) into the posterior air sacs.
E) into the anterior air sacs.

Question 22

Which of the following statements about insect respiration is false?

A) Spiracles are the air tubes that carry the respiratory gases.
B) Because O₂ diffuses more quickly in air than in water, the insect respiratory system is highly efficient.
C) Aquatic insects that carry air bubbles underwater use the bubble as a source of O₂.
D) Some insects have external gills.
E) All of the above are true; none is false.

Question 23

The respiratory system of insects consists of

A) branched air tubes called spiracles that supply capillaries.
B) branched air tubes called tracheae that supply capillaries.
C) branching gill systems that end in openings called tracheae.
D) branching gill systems that end in openings called spiracles.
E) extensive layers of gas exchange tissue just under the exoskeleton.

Question 24

Which of the following adaptations is not seen in fish gills?

A) A countercurrent exchange system
B) Bidirectional ventilation of the gills
C) Morphological features that increase the surface area available for gas exchange
D) Morphological features that decrease the path length for diffusion of the respiratory gases
E) Morphological features that maximize the efficiency of O₂ extraction

Question 25

Bird and fish respiratory systems are similar in that both

A) employ a countercurrent exchanger.
B) have air sacs.
C) function by means of unidirectional flow of the environmental medium over the gas exchange membranes.
D) consist of infoldings of the body.
E) All of the above

Question 26

Which of the following organisms does not require both external ventilation of its respiratory surfaces with the medium containing O₂ and internal ventilation of its respiratory surfaces with blood?

A) Crayfish
B) Rabbit
C) Insect
D) Squid
E) Bird

Question 27

Which of the following statements about respiratory adaptations is false?

A) Internalization of respiratory surfaces leads to the need for ventilation.
B) External gills are found only in invertebrates.
C) Some fishes ventilate their gills by swimming constantly with their mouths open.
D) In fish, water flows unidirectionally into the mouth, over the gills, and out from under the opercular flaps.
E) Desiccation of the respiratory surface is more likely to occur in lungs than in gills.

Question 28

Aquatic animals that lack an internal system for transporting O₂

A) often have flat, leaflike bodies.
B) are usually small.
C) may have a very thin body built around a central cavity through which water circulates.
D) have cells that are all close to the respiratory medium.
E) All of the above

Question 29

If a planet were discovered where the barometric pressure was 2,000 mm Hg and the air was 15 percent O₂, the partial pressure of its O₂ at sea level would be

A) 15 percent.
B) 15 mm Hg.
C) 133 mm Hg.
D) 300 mm Hg.
E) 30 percent.

Question 30

The rate of gas exchange in mammals is maximized by

A) an exceedingly high partial pressure of O₂ in the blood.
B) the opening of the larynx (voice box) into the trachea.
C) an enormous surface area for gas exchange.
D) the animals' small increase in size during inhalation.
E) the production of mucus and surfactants.

Question 31

Aquatic _______ are in a double bind, because their demand for oxygen increases as the temperature of their environment increases, but the oxygen content of water declines with increasing water temperatures.

A) insects
B) ectotherms
C) endotherms
D) plants
E) None of the above

Question 32

Which of the following is not an expected response from a fish to a drop in water temperature?

A) Increase in metabolism
B) Increase in amount of O₂ available
C) Decrease in blood flow
D) Decrease in O₂ consumption
E) All of the above are expected responses.

Question 33

Which of the following factors accounts for the efficiency of gas exchange in fish gills?

A) Maximized surface area
B) Minimized path length for diffusion
C) Countercurrent flow of blood and water over opposite sides of the gas exchange surfaces
D) Both a and b
E) All of the above

Question 34

Rapid gas exchange can be accomplished more easily in air than in water because

A) the O₂ content of water is higher than that of air.
B) the CO₂ content of water is higher than that of air.
C) O₂ diffuses more rapidly in water than in air.
D) water is more dense and viscous than air.
E) more energy is required to move air than to move water.

Question 35

Which of the following statements is not one of the reasons that diffusion of O₂ into an animal is more problematic than diffusion of CO₂ from an animal?

A) CO₂ is more soluble in water compared to O₂.
B) Cellular respiration produces less CO₂ than the O₂ that is consumed.
C) The CO₂ content of air is less than the O₂ content.
D) The atmospheric partial pressure of O₂ is greater than the atmospheric partial pressure of CO₂.
E) There is a greater concentration gradient from the cell to the atmosphere for CO₂ than for O₂.

Question 36

Which of the following statements about the air sacs of birds is false?

A) They connect with each other.
B) They occur in anterior and posterior pairs.
C) They make the bird's respiratory system more efficient than a mammal's.
D) They allow for one-way air flow through the lungs.
E) They provide an extra gas exchange surface.

Question 37

Which of the following is not an adverse consequence of tidal breathing as seen in mammals?

A) Absence of countercurrent gas exchange
B) Dead space
C) Residual volume
D) Short diffusion path length
E) Limit in the O₂ concentration gradient between air and blood

Question 38

Which of the following characterizes the lungs of mammals?

A) Air sacs
B) Tidal ventilation
C) Complete emptying in exhalation
D) Crosscurrent air flow
E) Countercurrent air flow

Question 39

Which of the following statements about the structure of the fish gill is false?

A) Afferent vessels bring blood to the gills, whereas efferent vessels take blood away from the gills.
B) Exchange of respiratory gases occurs within the lamellae of the gill filaments.
C) The efferent and afferent vessels are the counter-current flow system of the gill.
D) The lamellae greatly increase the surface area for gas exchange.
E) The opercular flaps enclose the gill chambers.

Question 40

The delicate gills of fishes are supported by _______ and _______.

A) flaps; gill arches
B) opercular flaps; gill filaments
C) gill filaments; gill arches
D) opercular flaps; a diaphragm
E) gill arches; a diaphragm

Question 41

Surfactant produced by cells lining the alveoli serves to

A) increase surface tension.
B) increase stretching of the alveolar walls.
C) assist muscular movements of breathing.
D) reduce cohesion of surface molecules.
E) reduce ciliary movement.

Question 42

Which of the following represents the correct air pathway during inhalation?

A) Pharynx, trachea, larynx, bronchi, alveoli
B) Larynx, trachea, pharynx, bronchi, alveoli
C) Trachea, larynx, pharynx, bronchi, alveoli
D) Trachea, larynx, pharynx, alveoli, bronchi
E) Pharynx, trachea, bronchi, larynx, alveoli

Question 43

Which of the following structures is the site of gas exchange in the lungs?

A) Alveoli
B) Bronchi
C) Bronchioles
D) Trachea
E) Both a and b

Question 44

Hemoglobin delivers O₂ to body cells from the red blood cells

A) until the hemoglobin is depleted of O₂.
B) until the partial pressures of O₂ in the two different cells are equivalent.
C) although the hemoglobin is never completely saturated.
D) by releasing O₂ to cells with a higher partial pressure of oxygen.
E) until the fluid pressure in the red blood cells is lower.

Question 45

If the O₂-binding curves were plotted for the following molecules, which curve would be to the left of all the others?

A) Fetal human hemoglobin
B) Adult llama hemoglobin
C) Adult human hemoglobin
D) Myoglobin
E) Fetal llama hemoglobin

Question 46

If the O₂-binding curves were plotted for the following types of hemoglobin at the pH levels indicated, which curve would be to the right of all the others?

A) Fetal human hemoglobin at pH 7.6
B) Adult human hemoglobin at pH 7.6
C) Adult human hemoglobin at pH 7.2
D) Fetal human hemoglobin at pH 7.2
E) Adult llama hemoglobin at pH 7.2

Question 47

Carbon monoxide (CO)

A) binds to hemoglobin with a higher affinity than O₂ does.
B) may be released by faulty furnaces or the burning of charcoal or kerosene in unventilated areas.
C) exposure may cause death from lack of O₂.
D) All of the above
E) None of the above

Question 48

The lungs expand in inhalation because

A) the diaphragm contracts upward.
B) the shoulder girdle moves upward.
C) the volume of the thoracic cavity increases.
D) lung tissue actively stretches.
E) the lung tissue rebounds from exhalation.

Question 49

If a new air pollutant were to destroy the surfactant in people's lungs, what effects might be expected?

A) Increased surface tension of the fluid lining the alveoli
B) Increased uptake of CO₂ from the environment
C) Increased effort needed to breathe
D) Decreased levels of hydrogen bonding in the fluid of the alveoli.
E) Both a and c

Question 50

Which of the following statements about surfactants in the lungs is false?

A) Water coating the respiratory surfaces of the lungs creates surface tension.
B) Surfactants increase the cohesive forces between water molecules.
C) Certain cells in the alveoli produce surfactants.
D) Surface tension influences the amount of effort required to inflate the lungs.
E) Premature infants suffer respiratory distress syndrome if natural surfactants are not present within the lungs.

Question 51

The process of exhalation is brought about by

A) the contraction of intercostal muscles.
B) elastic recoil of the lung tissues.
C) the contraction of the diaphragm.
D) complete collapse of the lung tissue.
E) low pressure in the thoracic cavity.

Question 52

Which of the following statements about O₂-binding curves is false?

A) A smaller decrease in P_O2 is needed for hemoglobin to drop from 100 percent to 75 percent saturation than for hemoglobin to drop from 75 percent to 50 percent saturation.
B) In normal metabolism, the body uses only the upper one-fourth of its oxygen-binding curve.
C) The blood normally carries an enormous reserve of O₂.
D) The steepest part of the O₂-binding curve results in a great release of O₂ for only a modest drop in P_O2.
E) The P_O2 of blood drops below about 40 mm Hg only during extreme exertion.

Question 53

Which part of the blood is most efficient at carrying oxygen?

A) Blood plasma solution
B) Blood plasma proteins
C) Blood platelets
D) Membrane molecules of red blood cells
E) Hemoglobin molecules of red blood cells

Question 54

In the following equation, which quantity represents the volume of your normal breath? Total lung capacity = residual volume + expiratory reserve volume + inspiratory reserve volume + tidal volume

A) Total lung capacity
B) Residual volume
C) Expiratory reserve volume
D) Inspiratory reserve volume
E) Tidal volume

Question 55

If the thoracic wall is punctured, air leaking in will cause the lung to collapse. Thus, in the normal, intact thoracic cavity,

A) lung expansion is passive.
B) air pressure is the same as it is on the outside.
C) a slight suction keeps lungs inflated.
D) breathing movements keep lungs inflated.
E) Both a and b

Question 56

Myoglobin benefits muscle cells by

A) binding with O₂ just as easily as hemoglobin does.
B) contributing to the elasticity of flight muscle in birds.
C) increasing the effectiveness of muscles used in short bursts.
D) releasing bound O₂ at lower P_O2 conditions than hemoglobin does.
E) using hemoglobin as a reserve source of oxygen.

Question 57

One effect of cigarette smoking on the lungs is

A) the removal of mucus from the airways.
B) the immobilization of cilia lining the airways.
C) the speeding of airflow through the airways.
D) increased surfactant action.
E) increased surface area in alveoli.

Question 58

Which of the following statements about the mechanics of ventilation is false?

A) If the pleural cavity is punctured, the lung may collapse.
B) As the diaphragm relaxes, air is expelled from the respiratory system.
C) As the diaphragm relaxes, pressure within the pleural cavities increases.
D) Less energy is expended during the exhalation phase than during the inhalation phase.
E) There is a slight positive pressure within the pleural cavities between breaths.

Question 59

Smokers cough frequently because

A) tar fills numerous alveoli.
B) a histamine response to the smoke narrows the airway.
C) cilia that typically eject mucus are paralyzed by the smoke.
D) coughing assists in release of surfactant, which is inhibited by smoking.
E) All of the above

Question 60

The lower side of the thoracic cavity is formed by the

A) diaphragm.
B) esophagus.
C) stomach.
D) ribs.
E) intercostal muscles.

Question 61

In acidic tissues, hemoglobin releases _______ it does in less acidic environments.

A) more O₂ than
B) less O₂ than
C) more CO₂ than
D) less CO₂ than
E) the same amount of O₂ and CO₂ as

Question 62

In which of the following P_O2 environments would hemoglobin release its O₂ most easily?

A) 30 mm Hg
B) 50 mm Hg
C) 70 mm Hg
D) 90 mm Hg
E) 110 mm Hg

Question 63

Which of the following statements about myoglobin is false?

A) Iron in the myoglobin molecule can bind to O₂.
B) Myoglobin is found in muscle cells.
C) Myoglobin has a lesser affinity for O₂ than hemo-globin does.
D) Diving mammals have high concentrations of myoglobin in their muscles.
E) Skeletal muscles can differ in their myoglobin content.

Question 64

Breathing rhythm is generated in the _______ and modified by neurons either in or above the _______.

A) medulla; pons
B) medulla; spinal cord
C) spinal cord; pons
D) spinal cord; cerebellum
E) cerebellum; medulla

Question 65

When humans have acclimated to high altitudes, their hemoglobin

A) is more saturated with O₂.
B) delivers more O₂ to tissues as the level of BPG increases.
C) is more concentrated in red blood cells.
D) shifts its O₂-binding curve to the left.
E) resembles fetal hemoglobin in terms of its O₂-binding function.

Question 66

Most of the CO₂ in the blood is transported as _______, and it is located mainly in the _______.

A) CO₂; plasma
B) H₂CO₃; plasma
C) HCO₃^-; plasma
D) carboxyhemoglobin; erythrocytes
E) HCO₃^-; erythrocytes

Question 67

Which of the following statements about the transport of respiratory gases by the blood is false?

A) The amount of O₂ that can dissolve directly in plasma is sufficient to support the resting metabolism.
B) By binding O₂, hemoglobin helps maintain the O₂ concentration gradient.
C) Internal ventilation of the gas exchange surfaces is dependent on blood flow.
D) Each hemoglobin molecule can carry a maximum of four O₂ molecules.
E) Molecules of O₂ are associated with the heme groups of hemoglobin.

Question 68

Which of the following is a benefit provided by fetal hemoglobin?

A) It transfers O₂ from adult hemoglobin to the fetus.
B) It releases O₂ at a lower partial pressure than adult hemoglobin does.
C) In the placenta, O₂ diffuses from adult hemoglobin to fetal hemoglobin.
D) At low O₂ pressures, it is less likely to pick up oxygen than adult hemoglobin is.
E) It occurs in higher density in red blood cells than adult hemoglobin does.

Question 69

Which of the following statements about the binding of oxygen by hemoglobin is false?

A) The percentage of completely O₂-saturated hemoglobin increases as P_O2 increases.
B) The oxygen-binding curve is S-shaped.
C) There is a narrow range of the O₂-binding curve where O₂ dissociation-association is rapid.
D) A very low P_O2 is required for all four hemoglobin subunits to bind to O₂.
E) If one subunit of a completely oxygen-saturated hemoglobin loses its O₂, the affinity of the remaining subunits for their O₂ increases.

Question 70

Neural control of breathing is a function of the

A) cerebrum.
B) diaphragm.
C) medulla.
D) olfactory lobe.
E) spinal cord.

Question 71

Breathing rhythm is generated in the _______ and is influenced by variation in levels of _______ in the blood.

A) medulla; CO₂ and O₂
B) medulla; CO₂ only
C) medulla; O₂ only
D) frontal lobe; CO₂ and O₂
E) frontal lobe; CO₂ only

Question 72

C. R. Bainton conducted an experiment in which he increased the workload of dogs by having them run on inclined treadmills and showed that respiratory rate responded to CO₂ levels. However, this success story followed an earlier experiment that did not support his hypothesis. In the earlier study, he

A) compared respiratory rate of dogs versus cats.
B) compared sleeping versus barking dogs.
C) changed the speed at which the dogs ran.
D) changed the dog's motivation by keeping them food-stressed.
E) injected dissolved O₂ into the dogs' arteries.

Question 73

Chemoreceptors on the surface of the medulla are sensitive to

A) O₂.
B) N₂.
C) surfactant.
D) CO₂ and the pH of the cerebrospinal fluid.
E) None of the above

Question 74

In studies of dogs running on treadmills, C. R. Bainton found that when he doubled the speed of the treadmill,

A) arterial CO₂ levels increased exponentially by a power of 2.
B) arterial CO₂ levels were unchanged.
C) respiratory rate was unchanged.
D) respiratory rate increased.
E) Both b and d

Question 75

Due to the activity of carbonic anhydrase, within the lung there is a concentration gradient of CO₂ from the erythrocyte to the _______, and a concentration gradient of _______ from the plasma to the _______.

A) plasma; HCO₃^-; plasma
B) plasma; HCO₃^-; lung
C) lung; CO₂; lung
D) lung; HCO₃^-; erythrocyte
E) lung; HCO₃^-; lung

Question 76

Unlike humans and other mammals, fishes respond to _______ to adjust their respiratory rate.

A) P_CO2
B) P_O2
C) P_N2
D) P_CO
E) turbidity

Question 77

Which of the following would increase the amount of oxygen diffusing from the lungs into the blood?

A) An increase in the binding rate of O₂ to hemoglobin
B) A decrease in the partial pressure of O₂ in the lungs
C) An increase in the partial pressure of O₂ in the blood
D) A decrease in the red blood cell count
E) An increase in the water vapor of air in the lungs

Question 78

Each molecule of hemoglobin, when fully saturated, carries _______ molecule(s) of oxygen.

A) 1
B) 2
C) 4
D) 20
E) nearly 100

Question 79

If the O₂-binding curves were plotted for adult hemoglobin under the following conditions, which curve would be to the right of all the others?

A) pH 7.6, little 2,3-bisphosphoglyceric acid
B) pH 7.6, much 2,3-bisphosphoglyceric acid
C) pH 7.2, little 2,3-bisphosphoglyceric acid
D) pH 7.2, much 2,3-bisphosphoglyceric acid
E) pH 7.4, little 2,3-bisphosphoglyceric acid

Question 80

Carbonic anhydrase is an enzyme in red blood cells that catalyzes a reaction between CO₂ and

A) HCO₃^-.
B) H₂CO₃.
C) hemoglobin.
D) O₂.
E) water.