21-4: Gas Exchange Flashcards Preview

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Flashcards in 21-4: Gas Exchange Deck (34)
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1
Q

Dalton’s Law

A

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

2
Q

partial pressure

A

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

3
Q

What is the main gas in our atmosphere?

A

nitrogen (78.6%)

4
Q

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

A

21%, .04%

5
Q

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

A

partial pressure gradients promote gas movements in the body

6
Q

PO2 in air

A

160

7
Q

PCO2 in air

A

.3

8
Q

PO2 in lungs

A

104

9
Q

PCO2 in lungs

A

40

10
Q

PO2 in tissues

A

<40

11
Q

PCO2 in tissues

A

> 45

12
Q

How is molecular oxygen carried in the blood?

A

dissolved in the plasma or bound to hemoglobin

13
Q

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

A

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

14
Q

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

A

4; rapid and reversible

15
Q

oxyhemoglobin

A

hemoglobin carrying O2 (HbO2)

16
Q

deoxyhemoglobin

A

hemoglobin that has released its O2 (HHb)

17
Q

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

A

partial pressure of oxygen (PO2)

18
Q

oxygen-hemoglobin dissociation curve

A

graph depicting the relationship between PO2 and % sat of Hb

19
Q

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

A

104; 98%

20
Q

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

A

40; 73%

21
Q

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

A

25%

22
Q

reserve supply

A

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

23
Q

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

A

40; large; rapidly delivered to the tissues

vigerous muscle activity, exercise

24
Q

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

A

temp increases; pH decreases; PCO2 increases

25
Q

carbon monoxide poisoning

A

outcompetes O2 for a spot on Hb

26
Q

carbon monoxide

A

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

27
Q

What is the danger of CO?

A

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

28
Q

How is CO2 transported in the blood?

A

dissolved in plasma
bound to Hb
as bicarbonate ions

29
Q

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

A

as bicarbonate ions (~70%)

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

30
Q

carbaminohemoglobin

A

carbon dioxide bound to Hb

31
Q

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

A

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-

32
Q

How is CO2 released during external respiration?

A

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

33
Q

Why does nitrogen have little effect in our bodies?

A

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

34
Q

When is nitrogen a danger?

A

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