BIO 162 Animals MIDTERM II Chapter 45

A single hemoglobin molecule consists of four subunits, each of which can bind an oxygen molecule. Cooperative binding is a phenomenon that affects hemoglobin's binding and release of oxygen. Which of the following statements accurately describe the effects of cooperative binding?

-Binding oxygen causes a conformational change in hemoglobin. -When an oxygen molecule binds to hemoglobin, the other subunits become more likely to bind oxygen. -When an oxygen molecule releases from hemoglobin, the other subunits become more likely to release oxygen.

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

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

At an atmospheric pressure of 870 mm Hg with 21 percent oxygen, the partial pressure of oxygen is _____.

182 mm Hg

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

A four-chambered heart. *Separate chambers help creates strong blood pressure and efficient oxygenation.

What would you predict if the curve were steeper than the one pictured?

A larger change in oxygen saturation of hemoglobin to a change in oxygen partial pressure.

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

A shallow river fed by a waterfall. *Shallow streams tend to be better oxygenated than deep ones.

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−).

Which process uses oxygen gas within cells?

Cellular respiration.

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.

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

Frog. *Two atria and one ventricle.

Which of the following does correctly represent blood flow through the heart?

From the right atrium to the right ventricle From the vena cava to the right atrium From the left ventricle to the aorta

What is the function of a circulatory system?

It brings a transport liquid into close contact with all cells in the body. *This transport liquid exchanges gases, nutrients, and wastes with the 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.

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.

Why are there no endothermic water-breathing animals?

Oxygen is more difficult to extract from water than from air. *Water breathers cannot extract sufficient oxygen to support the high metabolic rates required for endothermy.

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

Rising CO2

How would this curve likely differ for a person whose family has lived atop a mountain for thousands of years?

Shifted to the left. *These people would have a higher affinity for oxygen in their blood.

Which event occurs first during diastole?

The atria and ventricles are relaxed, and blood flows into the atria. *Diastole is the relaxation phase of the cardiac cycle during which the chambers of the heart are relaxed and blood can enter them passively.

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.

Which of the following respiratory systems is closely associated with the blood supply?

The skin of an earthworm The gills of a fish The lungs of a vertebrate

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. *The systolic blood pressure is the peak blood pressure, resulting from contraction of the ventricles.

Why did the experiment use different individuals in repeated trials?

To reduce biasing results from a single odd individual.

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.

Which of the following is a disadvantage of external gills?

Vulnerable to predation.

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.

Air-breathing insects carry out gas exchange _____.

across the finest branches of the trachea and cell membranes

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

as bicarbonate ions (HCO3 -)

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

bicarbonate dissolved in plasma

When the partial pressure of oxygen is 100 mm Hg (the partial pressure of oxygen in the lungs), hemoglobin is more likely to _____.

bind oxygen than release it

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

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

extracellular fluid capillary wall epithelial cells

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

fishes

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.

Voice sounds are produced by the _____.

larynx

From the pulmonary veins, blood flows to the _____.

left atrium

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

When the partial pressure of oxygen is 40 mm Hg (the partial pressure of oxygen in the tissues), hemoglobin is more likely to _____.

release oxygen than bind it

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

right atrium *Blood enters the right atrium from the anterior and posterior venae cavae.

Electrical impulses that trigger contraction of cardiac muscle cells in vertebrates originate in the _____.

sinoatrial node *The SA node, a region in the right atrium, contains pacemaker cells that initiate muscle contraction.

Circulatory systems compensate for _____.

the slow rate at which diffusion occurs over large distances

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

vein

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