B1Jimmyh.6

Front 1

H.6.1 Define partial pressure.

Back 1

Partial pressure is the pressure exerted by each component in a mixture. The pressure of a gas in a mixture is the same as it would exert if it occupied the same volume alone at the same temperature.

Front 2

H.6.2 Explain the oxygen dissociation curves of adult and fetal hemoglobin and myoglobin.

Back 2

The oxygen dissociation curve of adult hemoglobin is to the right of the oxygen dissociation curve of fetal hemoglobin. In other words, adult O2 saturation of hemoglobin is always lower than fetal O2 saturation of hemoglobin at the same O2 partial pressure. This is because fetuses don't have their own O2 source, so they must have high levels of O2 in hemoglobin for reserve.
When the O2 partial pressure is low, O2 diffuses out of hemoglobin very fast, so cells that are low on O2 can quickly receive much O2 (since they need it the most). The oxygen-storing protein myoglobin has a large reserve of O2 in case O2 concentrations get really low (e.g., sprinting). When this occurs, myoglobin very quickly releases its O2 to support the oxygen-depleted cells.

Front 3

H.6.3 Describe how carbon dioxide is carried by the blood, including the action of carbonic anhydrase, the chloride shift and buffering by plasma proteins.

Back 3

Carbon dioxide produced by body tissues diffuses into the interstitial fluid and into the plasma. Less than 10% remains in the plasma as dissolved CO2. The rest (70%) diffuses into red blood cells, where some (20%) is picked up and transported by hemoglobin. Most of the CO2 reacts with H20 in the red blood cells to form carbonic acid. Red blood cells contain the enzyme carbonic anhydrase, which catalyzes this reaction. Carbonic acid dissociates into a bicarbonate ion and hydrogen ion (H+). Hemoglobin (a plasma protein) binds most of the H+, preventing them from acidifying the blood. The reversibility of the carbonic acid- bicarbonate conversion also helps buffer the blood, releasing or removing H+ depending on the pH. Chlorine goes into the red blood cells when bicarbonate comes out. This is referred to as the chloride shift.

Front 4

Carbon dioxide produced by body tissues diffuses into the interstitial fluid and into the plasma. Less than 10% remains in the plasma as dissolved CO2. The rest (70%) diffuses into red blood cells, where some (20%) is picked up and transported by hemoglobin. Most of the CO2 reacts with H20 in the red blood cells to form carbonic acid. Red blood cells contain the enzyme carbonic anhydrase, which catalyzes this reaction. Carbonic acid dissociates into a bicarbonate ion and hydrogen ion (H+). Hemoglobin (a plasma protein) binds most of the H+, preventing them from acidifying the blood. The reversibility of the carbonic acid- bicarbonate conversion also helps buffer the blood, releasing or removing H+ depending on the pH. Chlorine goes into the red blood cells when bicarbonate comes out. This is referred to as the chloride shift.

Back 4

The Bohr shift helps the body release more O2 to respiring tissues when the pH is more acidic. During exercise, a lot of CO2 is produced, which results in larger amounts of hydrogen ions that acidify the blood. Thus, the Bohr shift lets the body know it's exercising.

Front 5

H.6.5 Explain how and why ventilation rate varies with exercise.

Back 5

During inhalation, the intercostal muscles and the diaphragm contract. The volume of the lungs increases as the diaphragm moves down and the rib cage expands. Air pressure in the lungs falls below that of the atmosphere and air rushes into the lungs. Exhalation occurs when the rib muscles and diaphragm relax, restoring the thoracic cavity to its smaller volume. Thus pressure becomes greater in lungs than in the atmosphere and air rushes out. Action of the intercostal muscles in increasing lung volume is most important during vigorous exercise. Increase in lung volume during shallow inhalation results from the action of the diaphragm.

Front 6

H.6.6 Outline the possible causes of lung cancer and asthma and their effects on the gas exchange system.

Back 6

Smoking and inhaling other carcinogens (e.g., polluted areas, coal) may cause lung cancer. The effect of lung cancer is that large cancerous cells in lungs reduce their surface area. Reaction to exercise and stress may cause asthma. The effect of asthma is that lung tissues swell, so they constrict the area of O2 absorption. Both lung cancer and asthma result in efficient gas exchange.

Front 7

H.6.7 Explain the problem of gas exchange at high altitudes and the way the body acclimatizes.

Back 7

Mountain sickness may occur when a person travels quickly from a low to high altitude. Over a period of time the person becomes acclimatized: red blood cell production and ventilation rate increase. People living permanently at high altitude have greater lung surface area and larger vital capacity than those living at sea level.