Mastering Biology Chapter 45

Calculate the partial pressure of oxygen at an atmospheric pressure of 500 mm Hg.

105 mmHg. This value was determined by multiplying the atmospheric pressure, 500 mm Hg, by 0.21, the fraction of air that is O2.

Which of the following promotes oxygen release from hemoglobin?

A decrease in pH.

The majority of carbon dioxide is carried in blood as _____.

Bicarbonate dissolved in plasma.

Which process uses oxygen gas within cells?

Cellular respiration

Which of the following does NOT correctly represent blood flow through the heart?

From the right ventricle to the left ventricle

Voice sounds are produced by the _____.

Larynx

A blood vessel that takes blood to the heart is a(n) _____.

Vein

An anthropologist discovers the fossilized heart of an extinct animal. The evidence indicates that the organism's heart was large, was well-formed, and had four chambers, with no connection between the right and left sides. A reasonable conclusion supported by these observations is that the _____.

animal was endothermic and had a high metabolic rate

Most carbon dioxide is carried from the body tissues to the lungs _____.

as bicarbonate ions (HCO3 -). Most carbon dioxide released from body tissues combines with water to form carbonic acid, which then breaks up into hydrogen and bicarbonate ions.

Which barrier(s) must O2 and CO2 cross to pass between air and blood inside lungs?

capillary wall, extracellular fluid, epithelial cells

The Bohr shift on the oxygen-hemoglobin dissociation curve is produced by changes in _____.

pH

Which of the following is most likely to be found in a terrestrial animal with high activity rates?

A four-chambered heart

Which of the following aquatic habitats has the highest oxygen content per unit area?

A shallow river fed by a waterfall. Waterfalls are highly oxygenated aquatic environments because of the exposure of the water to air and the incorporation of air bubbles. Also, shallow streams tend to be better oxygenated than deep one

Air-breathing insects carry out gas exchange _____.

Across the finest branches of trachea and cell membranes

Which lung structure is a tiny sac that functions as an interface between air and blood?

Alveolus

How is most carbon dioxide transported from tissues to the lungs?

As bicarbonate ions (HCO3−).

Hemoglobin and hemocyanin _____.

Both transport oxygen

In the blood most of the oxygen that will be used in cellular respiration is carried from the lungs to the body tissues _____.

Combined with hemoglobin.

Most of the carbon dioxide produced by humans is _____.

Converted to bicarbonate ions by an enzyme in red blood cells

If other factors are equal, which of the following environments would have the highest level of dissolved oxygen?

Cool freshwater at a low elevation

True or false? The driving force for the unloading of oxygen from hemoglobin into tissues is the difference in PCO2 levels between the blood and body tissues.

False. The PCO2 levels affect the diffusion of carbon dioxide; the driving force for the diffusion of oxygen from hemoglobin into tissues is the difference in PO2 levels between the blood (100 mm Hg when oxygenated) and body tissues (40 mm Hg at rest).

True or false? The pressure inside the human chest cavity is always positive, so the lungs stay relatively inflated even upon exhalation.

False. The lungs stay relatively inflated even upon exhalation because the pressure inside the chest cavity is always negative.

True or false? The circulatory systems of land-dwelling vertebrates are composed of two pumping circuits: the systemic circulation, which is a lower-pressure circuit to the lung, and the pulmonary circulation, which is a higher-pressure circuit to the rest of the body.

False. The pulmonary circulation is the lower-pressure circuit to the lung, whereas the systemic circulation is the higher-pressure circuit to the rest of the body.

An decrease from pH 7.4 to pH 7.2 causes hemoglobin to _____.

Give up more of its oxygen molecules

What is the function of a circulatory system?

It brings a transport liquid into close contact with all cells in the body.

What is the function of the left ventricle?

It pumps oxygenated blood around the body via the systemic circulation.

Which feature is common to gills, lungs, and tracheae?

Large surface area

From the pulmonary veins, blood flows to the _____.

Left atrium

Which of the following is an accurate comparison of vertebrate lungs?

Mammals have more alveolar surface area than frogs.

Where would oxygen partial pressure be the highest?

Mountain stream. Cold water and heavy mixing creates conditions with high oxygen.

The primary functions of the _____ are to warm, filter, and humidify air.

Nasal cavity

From the capillaries of the abdominal organs and hind limbs, blood flows to the _____.

Posterior vena cava

Blood returns to the heart via the _____.

Pulmonary veins

From the anterior vena cava, blood flows to the _____.

Right atrium

When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?

Rising carbon dioxide

Which event occurs first during diastole?

The atria and ventricles are relaxed, and blood flows into the atria.

Which of the following statements about the oxygen-hemoglobin interaction is true?

The binding of one oxygen molecule to hemoglobin stimulates the binding of other oxygen molecules.

Why do the circulatory systems of land vertebrates have separate circuits to the lungs and to the rest of the body?

The large decrease in blood pressure as blood moves through the lungs may prevent efficient circulation through the rest of the body.

When you are jogging, your muscles are using more oxygen and releasing more carbon dioxide into the blood than when you are at home on the couch. Which of the following would occur during your jog?

The medullary respiratory center would detect rising carbon dioxide levels.

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

The partial pressure of oxygen in the air at high elevations is lower than at sea level

Which of the following respiratory systems is NOT closely associated with the blood supply?

The tracheal system of an insect

Which event of the cardiac cycle occurs when systolic blood pressure is measured?

The ventricles contract, carrying blood into the aorta, and blood flows into the relaxed atria.

True or false? The lungs of humans form from the embryonic foregut.

True. Digestive organs such as the stomach and part of the small intestine also develop from the foregut.

Which of the following statements about blood circulation in the body is true?

Valves prevent the backflow of blood into the atria and ventricles.

Which of the following occurs in response to a drop in blood pressure?

Veins constrict. This constriction shifts blood volume toward the heart and arteries, maintaining blood flow to vital organs.

By picking up hydrogen ions, hemoglobin prevents the blood from becoming too _____.

acidic. If not carried by hemoglobin, hydrogen ions would reduce the pH, or increase the acidity, of the blood.

Countercurrent exchange in the fish gill helps to maximize _____.

diffusion

The only vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart are the _____.

fish

Which of the following animals has a three-chambered heart?

frog

Why is the pharmacological reactivation of fetal hemoglobin in a patient with sickle-cell anemia often a successful treatment? Fetal hemoglobin _____.

has a higher affinity for oxygen than does adult hemoglobin.

A shift to the right of the oxygen-hemoglobin equilibrium curve represents _____.

increased oxygen delivery to a tissue. A shift to the right—representing a pH decrease—makes hemoglobin more likely to release oxygen to tissues with low pH.

Circulatory systems compensate for _____.

the slow rate at which diffusion occurs over large distances

Which of the following is the correct sequence of blood flow in birds and mammals?

vena cava → right atrium → right ventricle → pulmonary artery

Air moves in and out of the tracheal system of an exercising insect by ______.

ventilation of the tracheae due to contraction of muscles around the tracheae. The muscles compress and dilate the tracheae, producing pressure changes in gases.