Week 12 Mastering Biology

Atmospheric pressure at sea level is equal to a column of 760 mm Hg. Oxygen makes up 21 percent of the atmosphere by volume. The partial pressure of oxygen (PO2) in such conditions is _____.

160 mm Hg

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

182 mm Hg

What would you predict if the curve were steeper than the one pictured? See Section 42.4 (Page)

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

Altitude sickness occurs when a hiker ascends to altitudes where the density of oxygen is low. Carbonic anhydrase inhibitors cause less movement of carbonic acid toward carbon dioxide production and are used as a prophylactic treatment of altitude sickness. How does this treatment decrease the symptoms of high altitude sickness?

An increase in blood acidity leads to an increase in ventilation.

In what way does hemoglobin act as a buffer against changes in blood pH?

Hemoglobin binds some of the excess protons released by carbonic acid.

How would this curve likely differ for a person whose family has lived atop a mountain for thousands of years? See Section 42.4 (Page) .

Shifted to the left

Why is breathing more difficult at high altitudes, such as at the top of Mount Everest? See Section 42.2 (Page) .

The lower partial pressure of oxygen in the atmosphere reduces the rate of diffusion of oxygen into your 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

The exhalation of air from human lungs is driven by ________.

a decrease in the volume of the thoracic cavity with an associated increase in thoracic pressure

You are a physician, and you are seeing a patient who complains of abnormal fatigue during exercise. You find that the immediate problem is a buildup of carbon dioxide in the tissues. What is the most likely cause?

abnormal carbonic anhydrase

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

acidic

In mammals, gas exchange between the atmosphere and the pulmonary blood occurs in the ________.

alveoli

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

as bicarbonate ions (HCO3 -)

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 carbonic anhydrase, an enzyme in red blood cells

To become bound to hemoglobin for transport in a mammal, atmospheric molecules of oxygen must cross ________.

five membranes-in and out of the cell lining the lung, in and out of the endothelial cell lining an alveolar capillary, and into the red blood cell-to bind with hemoglobin

An increase in blood carbon dioxide content causes hemoglobin to ________.

increase its binding of H+

A key aspect of cooperative binding by hemoglobin is that ___________. See Section 42.4 (Page) .

it permits rapid uptake of oxygen in the lungs and greater delivery of oxygen once blood reaches capillaries in the body's tissues

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

neurons in contact with cerebrospinal fluid monitor pH and use this measure to control breathing

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

pH

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

rising carbon dioxide

Air rushes into the lungs of humans during inhalation because ________.

the rib muscles and diaphragm contract, increasing the lung volume and decreasing the pressure within the lungs

In which location would you expect the oxygen concentration to be the lowest?

within tissues