21-4: Gas Exchange

Question 1

Dalton’s Law

Answer 1

the total pressure exerted by a mixture of gasses is the sum of the pressures exerted independently by each gas in the mixture

Question 2

partial pressure

Answer 2

the pressure a gas exerts in a mixture of gases, determined by multiplying the percentage of the gas in the mixture by the total pressure of the mixture

Question 3

What is the main gas in our atmosphere?

Answer 3

nitrogen (78.6%)

Question 4

Oxygen makes up about __% of the atmosphere, and CO2 about __%.

Answer 4

21%, .04%

Question 5

Why are certain gases moving into the body and not others?

Answer 5

partial pressure gradients promote gas movements in the body

Question 6

PO2 in air

Answer 6

160

Question 7

PCO2 in air

Answer 7

.3

Question 8

PO2 in lungs

Answer 8

104

Question 9

PCO2 in lungs

Answer 9

40

Question 10

PO2 in tissues

Answer 10

<40

Question 11

PCO2 in tissues

Answer 11

> 45

Question 12

How is molecular oxygen carried in the blood?

Answer 12

dissolved in the plasma or bound to hemoglobin

Question 13

What is the main way molecular oxygen is carried in the blood?

Answer 13

bound to hemoglobin - most (~98%) of O2 is bound to this carrier molecule

only ~2% is dissolved in the plasma since O2 is relatively insoluble in water

Question 14

Each molecule of Hb can combine with __ molecules of oxygen. This binding process is ____.

Answer 14

4; rapid and reversible

Question 15

oxyhemoglobin

Answer 15

hemoglobin carrying O2 (HbO2)

Question 16

deoxyhemoglobin

Answer 16

hemoglobin that has released its O2 (HHb)

Question 17

What determines whether O2 binds to or is released from hemoglobin?

Answer 17

partial pressure of oxygen (PO2)

Question 18

oxygen-hemoglobin dissociation curve

Answer 18

graph depicting the relationship between PO2 and % sat of Hb

Question 19

In the capillaries of the lungs, PO2 = __ and Hb is __% sat.

Answer 19

104; 98%

Question 20

In tissues, where PO2 = __, Hb is __% sat.

Answer 20

40; 73%

Question 21

Under resting conditions, __% of O2 bound to Hb is unloaded to tissues

Answer 21

25%

Question 22

reserve supply

Answer 22

75% of O2 remains bound to Hb (venous reserve) for when oxygen demand increases

Question 23

When PO2 drops below ___, ____ amounts of O2 are ____. What can cause this drop?

Answer 23

40; large; rapidly delivered to the tissues

vigerous muscle activity, exercise

Question 24

If temperature __, pH ___, or PCO2 ___, O2 disassociates from Hb more readily.

Answer 24

temp increases; pH decreases; PCO2 increases

Question 25

carbon monoxide poisoning

Answer 25

outcompetes O2 for a spot on Hb

Question 26

carbon monoxide

Answer 26

colorless, odorless gas found in vehicle exhaust, burning wood or fossil fuels, cigarette smoke

Question 27

What is the danger of CO?

Answer 27

it combines with Hb 200x faster than O2, preventing O2 from binding. This results in hypoxia

Question 28

How is CO2 transported in the blood?

Answer 28

dissolved in plasma
bound to Hb
as bicarbonate ions

Question 29

What is the main way CO2 is transported in the blood during internal respiration?

Answer 29

as bicarbonate ions (~70%)

~7% is carried in the blood plasma as a dissolved gas and ~23% is carried bound to Hb

Question 30

carbaminohemoglobin

Answer 30

carbon dioxide bound to Hb

Question 31

How is CO2 converted to a bicarbonate ion (HCO3-)?

Answer 31

CO2 enters RBCs, combines with H2O to form carbonic acid, which quickly disassociates into H+ and bicarbonate ions. Catalyzed by carbonic anhydrase

CO2 + H2O –> H2CO3 –> H+ + HCO3-

Question 32

How is CO2 released during external respiration?

Answer 32

internal respiration events are reversed:

CO2 gas dissolved in plasma diffuses out of blood and into alveoli

CO2 bound to Hb splits due to pressure differences and diffuses into alveoli

Bicarbonate ion reaction is reversed, CO2 diffuses along its partial pressure gradient from teh pulmonary blood into the alveoli

Question 33

Why does nitrogen have little effect in our bodies?

Answer 33

has low solubility at sea level and Hb doesn’t have a binding site

Question 34

When is nitrogen a danger?

Answer 34

for deep sea divers, since N2 can dissolve inthe blood as atmospheric pressure goes up - if a diver comes up too fast, N2 gas bubbles out of his blood causing the bends, nausea, and seizures