Gas Exchange and Transport

Question 1

Atmospheric air

Answer 1

a gaseous mixture of approximately 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, and minute amounts of other gases.

Question 2

partial pressure of oxygen in atmospheric air

Answer 2

(pO2)

approximately 160 mmHg

Question 3

partial pressure of carbon dioxide

Answer 3

(pCO2)

approximately 0.3 mmHg

Question 4

When air and water meet at the respiratory membrane

Answer 4

each gas diffuses along its concentration gradient until its partial pressure in air equals its partial pressure in water

Question 5

pO2

Answer 5

relatively higher in alveolar air, blood “loads” oxygen in the lungs

Question 6

pCO2

Answer 6

relatively higher in alveolar blood, it “unloads” carbon dioxide in lungs

Question 7

pO2 in alveolar air versus pO2 in the blood

Answer 7

pO2 in alveolar air is approximately 104 mmHg, while pO2 in the blood entering the capillaries is approximately 40 mmHg

Question 8

oxygen in alveolar gas exchange

Answer 8

will diffuse along a pressure gradient out of the alveoli and into the blood

Question 9

pCO2 in the blood versus in alveolar air

Answer 9

pCO2 in the blood entering the capillaries is approximately 46 mmHg while pCO2 in alveolar air is approximately 40 mmHg

Question 10

The rate of alveolar gas exchange at high altitudes

Answer 10

the pO2 is low; pressure gradient is smaller and less oxygen diffuses into blood

Question 11

The rate of alveolar gas exchange under hyperbaric conditions

Answer 11

pO2 is very high; pressure gradient is great, more oxygen diffuses into blood

Question 12

Solubility of the gases in respiratory fluids

Answer 12

• Oxygen is only 5% soluble in blood plasma
• nitrogen is only 2.5% soluble in blood plasma
• carbon dioxide is the most soluble of the gases in blood plasma
  it quickly diffuses even though it has smallest pressure gradient

Question 13

Respiratory membrane

Answer 13

relatively thin so gases diffuse across it without difficulty

Question 14

Surface area of the respiratory membrane

Answer 14

large enough to facilitate gas exchange

Question 15

oxygen carried in the blood plasma

Answer 15

oxygen does not dissolve easily, so only 1.5% is carried in the blood plasma

Question 16

formation of oxyhemoglobin (HbO2)

Answer 16

oxygen diffuses into the blood and quickly moves into erythrocytes where it combines with the heme portion of hemoglobin to form oxyhemoglobin

Question 17

amount of oxygen carried as oxyhemoglobin

Answer 17

98.5%

Question 18

oxyhemoglobin dissociation curve

Answer 18

the extent to which oxygen binds reversibly with hemoglobin depends on pO2 according to the oxyhemoglobin dissociation curve

Question 19

oxyhemoglobin dissociation curve- at low pO2

Answer 19

(in tissue capillaries)- hemoglobin is only partially saturated

Question 20

oxyhemoglobin dissociation curve- at high pO2

Answer 20

(in pulmonary capillaries) - hemoglobin becomes fully saturated

Question 21

pCO2 in tissue cells

Answer 21

is approximately 45 mmHg, while pCO2 in tissue capillaries is about 40 mmHg

Question 22

carbon dioxide diffusion

Answer 22

CO2 will diffuse along its pressure gradient out of the cells through interstitial space, into tissue capillaries where much of it will enter erythrocytes

Question 23

carbonic anhydrase (CAH)

Answer 23

catalyzes reaction between carbon dioxide and water to form carbonic acid which dissociates into bicarbonate and hydrogen ions

Question 24

Chloride shift

Answer 24

most bicarbonate ions are pumped out of erythrocytes and replaced with chloride ions duirng chloride shift, which maintains balance of anions

Question 25

hyrdogen ions combine with

Answer 25

hemoglobin to prevent a change in blood pH

Question 26

pO2 in tissue capillaries versus tissue cells

Answer 26

pO2 in tissue capillaries is about 95 mmHg, while pO2 in tissue cells is about 40 mmHg

Question 27

oxygen diffusion

Answer 27

O2 will diffuse along its pressure gradient out of the blood through interstitial fluid into cells

Question 28

how does pO2 in the tissues affect the rate at which oxygen is unloaded from oxyhemoglobin

Answer 28

low pO2 in the tissues promotes elease of oxygen from oxyhemoglobin

Question 29

how does temperature affect the rate at which oxygen is unloaded from oxyhemoglobin

Answer 29

an increase in temperature causes more oxygen to be released from oxyhemoglobin

Question 30

how does pH affect the rate at which oxygen is unloaded from oxyhemoglobin

Answer 30

a drop in pH causes more oxygen to be released from oxyhemoglobin (Bohr effect)

Question 31

What affect do hydrogen ions have when they bind to hemoglobin

Answer 31

when hydrogen ions bind to hemoglobin- the 3-dimensional structure is altered and it reduces its oxygen- carrying capacity

Question 32

BPG

Answer 32

a metabolic byproduct produced when erythrocytes break down glucose by glycolysis and its presence promotes oxygen unloading

Question 33

Carbon monoxide

Answer 33

a colorless, odorless gas produced by incomplete combustion

Question 34

carbon monoxide binding to hemoglobin versus oxygen binding to hemoglobin

Answer 34

carbon monoxide binds to hemoglobin 200 times more tightly than oxygen binds to hemoglobin, which drastically reduces oxygen-carrying capacity of hemoglobin

Question 35

How much of the carbon dioxide generated is trasnported as dissolved gas in blood plasma

Answer 35

5%

Question 36

The carbon dioxide transported as dissolved gas in blood plasma accounts for how much of carbon disoxide exchange between the blood and the alveolar capillaries

Answer 36

7%

Question 37

How much of the carbon dioxide generated is trasnported as carbaminohemoglobin

Answer 37

5%

Question 38

carbaminohemoglobin

Answer 38

when carbon dioxide binds to amino groups on the polypeptide chains of hemoglobin

Question 39

The carbon dioxide transported as carbaminohemoglobin accounts for how much of carbon disoxide exchange between the blood and the alveolar capillaries

Answer 39

23%

Question 40

a low pO2

Answer 40

results in less saturated Hemoglobin

Question 41

How much of the carbon dioxide generated is trasnported as bicarbonate ions in blood plasma

Answer 41

90%

Question 42

The carbon dioxide transported as bicarbonate ions in blood plasma accounts for how much of carbon disoxide exchange between the blood and the alveolar capillaries

Answer 42

70%

Question 43

bicarbonate ions combine with hydrogen ions to do what

Answer 43

reform carbonic acid; carbonic anhydrase enzyme breaks it down into carbon dioxide and water

Question 44

reverse chloride shift

Answer 44

chloride ions are removed from erythrocytes

Question 45

where does carbon dioxide diffuse in order to be exhaled

Answer 45

out of the blood into alveoli

Question 46

blood gives up dissolved carbon dioxide gas and carbon dioxide from carbaminohemoglobin _____ _____ than it gives up CO2 from bicarbonate ions

Answer 46

more easily

Question 47

an increase of pCO2 has what affect on oxyhemoglobin

Answer 47

causes oxyhemoglobin to release its oxygen and transport more carbon dioxide

Question 48

Chemoreceptors

Answer 48

in the medulla oblongata, carotid arteries, and aorta are senstive to changes in hydrogen ions, carbon dioxide, and oxygen in the blood

Question 49

control of breathing during rest

Answer 49

aimed primarily at regulating the concentration of hydrogen ions in the brain

Question 50

drowning victims

Answer 50

have water in their lungs because H+ builds up as result of insufficient ventilation (involuntary inspiration)

Question 51

Normal blood pH

Answer 51

between 7.35 and 7.45

Question 52

respiratory acidosis

Answer 52

when blood pH falls below 7.35 because of problems with pulmonary ventilation

Question 53

respiratory alkalosis

Answer 53

when blood pH rises above 7.45 because of problems with pulmonary ventilation

Question 54

common cause of respiratory acidosis

Answer 54

a slight increase in pCO2

Question 55

when pCO2 rises above 43 mmHg

Answer 55

hypercapnia occurs and causes acidosis

Question 56

what do chemoreceptors signal when acidosis occurs and why

Answer 56

inspiratory area to increase rate and depth of breathing

Question 57

hyperventilation

Answer 57

allows the body to exhlae carbon dioxide faster than it forms; will shift carbonic acid reaction to left and get rid of hydrogen ions to bring pH up to "normal"

Question 58

common cause of respiratory alkalosis

Answer 58

a slight decrease in pCO2

Question 59

when pCO2 falls below 37 mmHg

Answer 59

hypocapnia occurs and causes alkalosis

Question 60

what do chemoreceptors signal when alkalosis occurs

Answer 60

they do not signal inspiratory area- so rate and depth of brathing remain slow and shallow

Question 61

hypoventilation

Answer 61

allows body to accumulate carbon dioxide faster than it can be exhaled; will shift carbonic acid reaction to right and produce more hydorgen ions to bring pH down to "normal"

Question 62

oxygen concentration and the impact on respiration

Answer 62

oxygen concentration usually has little impact on respiration because hemoglobin is usually highly saturated - only if arterial pO2 falls dramatically will ventilation be affected.