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PHGY-210 > Respiration - Lecture 4 > Flashcards

Respiration - Lecture 4 Flashcards

1
Q

The amount of dissolved gas carried by the blood is directly proportional to…

A

the partial pressure of the gas

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2
Q

What kind of amount of O2 is dissolved in the blood?

A

a very small amount

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3
Q

What is O2 linearly proportional to?

A

PO2

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4
Q

How much O2 is in 100 mL of plasma?

A

0.3 mL

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5
Q

O2 consumption is much ___ than what can be supplied from the amount dissolved in the blood

A

greater

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6
Q

What is the rate of consumption of O2 at rest?

A

300 mL O2/min

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7
Q

What allows whole blood to take up to 65 times as much O2 as plasma at PO2 of 100 mmHg?

A

hemoglobin

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8
Q

How much does hemoglobin constitute of the total weight of red blood cells?

A

1/3

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9
Q

How many subunits is hemoglobin made of?

A

4

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10
Q

What is each subunit of hemoglobin made of?

A

a heme joined to a globin

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11
Q

What does heme contain?

A

an Fe++ ion

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12
Q

What can one Fe++ ion bind?

A

1 molecule of O2

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13
Q

Why is Hb essential for the transport of O2 by blood?

A

because it combines rapidly and reversibly with O2

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14
Q

At PO2 of 100 mmHg, what is the total amount of O2 physically dissolved in the blood?

A

0.3 vol.%

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15
Q

At PO2, of 100 mmHg, what is the total amount of O2 bound to Hb?

A

19.5 vol.%

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16
Q

What is the total amount of O2 in arterial blood?

A

about 20 vol.%

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17
Q

Does the O2 that is bound to Hb contribute to the PO2 of the blood?

A

no

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18
Q

What kind of molecules are responsible for PO2?

A

molecules that are physically dissolved in the blood plasma

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19
Q

What does the PO2 of the plasma determine?

A

the amount of O2 that combines with Hb

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20
Q

What does the HbO2 dissociation curve determine?

A

the amount of O2 carried by Hb for a given partial pressure of O2

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21
Q

When is the HbO2 dissociation curve flat? What levels?

A

at high values of PO2, at alveolar levels

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22
Q

When is the HbO2 dissociation curve steep?

A

at low values of PO2, at peripheral tissue levels

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23
Q

What happens to the amount of O2 bound to Hb at high values of PO2?

A

they remain constant

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24
Q

How much does PO2 have to drop in order for HbO2 to drop significantly?

A

60 mmHg

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25
Q

What happens to Hb at high pressures?

A

it becomes saturated

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26
Q

What happens to Hb at low pressures? Why?

A

it becomes desaturated to supply oxygen to tissues (e.g. exercise)

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27
Q

What happens to HbO2 at low PO2?

A

it dissociates into Hb and O2 more readily

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28
Q

Why is there a significant drop in PO2 and %HbO2 at the tissue level?

A

because it is where metabolic processes happen and its to match tissue O2 supply to tissue O2 need

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29
Q

As blood enters the tissue capillaries, plasma PO2 is ___ than interstitial fluid PO2

A

greater

30
Q

O2 readily diffuses across the capillary membrane into the ____

A

interstitial fluid

31
Q

What happens to plasma PO2 and O2 when O2 readily diffuses across the capillary membrane into the ISF?

A

plasma PO2 decreases and O2 diffuses out of the erythrocytes into the plasma

32
Q

What happens to the HbO2 when the erythrocytes PO2 decreases?

A

it dissociates into Hb and O2

33
Q

After diffusing into the interstitial fluid, where does the O2 go?

A

into the cells

34
Q

What determines the affinity of Hb for O2?

A

its quaternary structure

35
Q

What increases the affinity of the second binding for O2?

A

the combination of the first heme in Hb with O2

36
Q

What increases the affinity of Hb?

A

the conformational change as O2 binds to Hb

37
Q

Where is myoglobin found?

A

in skeletal muscle

38
Q

Myoglobin resembles Hb but binds only…

A

one O2 molecule

39
Q

What shape is the O2 dissociation curve?

A

sigmoid shape

40
Q

What shape is the O2-myoglobin curve?

A

hyperbolic

41
Q

When does myoglobin release its O2 in a O2-myoglobin curve?

A

at very low PO2

42
Q

What does the total amount of O2 in the blood depend on?

A

Hb concentration

43
Q

How much is the normal amount of Hb in a person?

A

14 g/100 mL

44
Q

How much Hb does someone who has anaemia have?

A

10g/100 mL

45
Q

When does the Bohr Effect shift the HbO2 dissociation curve to the right?

A

when blood CO2 or temperature increases or blood pH decreases

46
Q

What does it mean when the HbO2 dissociation curve shifts to the right?

A

for a given drop in PO2, an additional amount of O2 is released from Hb to the working tissues

47
Q

When does the Bohr equation shift the HbO2 dissociation curve to the left?

A

when blood CO2 or temperature decreases or blood pH increases

48
Q

What has an extremely high affinity for the O2 binding sites in hemoglobin?

A

CO

49
Q

What reduces the amount of O2 bound to hemoglobin?

A

CO

50
Q

What does CO do to the O2-hemoglobin curve?

A

it shifts it to the left

51
Q

What are the 3 ways CO2 is carried in the blood?

A
  1. physically dissolved (10)
  2. combined with Hb to form HbCO2 (11%)
  3. as bicarbonate (79%)
52
Q

Where does CO2 diffuse?

A

into the plasma where it is physically dissolved

53
Q

What does CO2 combine with in Hb?

A

the globin portion

54
Q

Why does CO2 combine with the globin portion and not the heme portion of Hb?

A

so that there is no competition for binding on Hb

55
Q

What does CO2 combine with to produce carbonic acid?

A

water

56
Q

What aids the diffusion of CO2 in the erythrocytes?

A

carbonic anhydrase

57
Q

What are the 2 formulas for bicarbonate?

A
  1. CO2 + H2O -> H2CO3 (carbonic acid)
  2. H2CO3 -> HCO3 + H+
58
Q

All of the reactions involved with CO2 are…

A

reversible

59
Q

What happens to the production of HbCO2, HCO3, and H+ if the CO2 production increases?

A

they also increase

60
Q

What happens to HCO3 when blood PCO2 decreases?

A

it gets transformed into H2CO3 and further into CO2 and H2O, and HBCO2 generating Hb and CO2

61
Q

What are the two reactions that happen when the blood PCO2 decreases?

A
  1. H+ + HCO3 -> H2CO3 -> H2O + CO2
  2. HbCO2 -> H2O + CO2
62
Q

Why is there a decrease in blood PCO2 when there is a net diffusion from the blood into the alveoli?

A

because the blood PCO2 is higher than alveolar PCO2

63
Q

Hb free of O2 may combine with what?

A

H+

64
Q

What is the reaction of the addition of H+ to Hb?

A

H+ + HbO2 -> HHb + O2

65
Q

What is the preferred way to transport CO2 in the body?

A

HCO3

66
Q

When Hb is free of O2 and combines with H+, it acts as a…

A

buffer

67
Q

What happens when there is a presence of reduced Hb in the tissue capillaries?

A

it helps with the blood loading of CO2

68
Q

When do you carry more CO2?

A

when your blood is deoxygenated

69
Q

Which kind of blood can carry more CO2 than arterial blood?

A

venous blood

70
Q

What influences the CO2 dissociation curve by shifting it to the right?

A

the O2 saturation of blood

PHGY-210 (36 decks)

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