Phgy 210: Respiration: Transport Of O2/co2

Front 1

What does Henry's Law state?

Back 1

Amount of dissolved gas carried by the blood is directly proportional to the partial pressure of the gas
(Henry's law: # of gas molecules dissolved in a liquid is proportional to the partial P of the gas above the liquid)

Front 2

How much O2 is dissolved in the blood?

Back 2

Very small amount
Linearly proportional to PO2
(In 100ml of blood, 0.3ml of O2 => 0.3 % by volume)

Front 3

What is O2 rate at rest?

Back 3

300ml O2/min
(O2 consumption by the blood at rest is greater than the amount of dissolved in the blood)

Front 4

What role does Hb have in O2 consumption?

Back 4

Allows whole blood to pick up 65x as much O2 as plasma (at P O2 = 100mm Hg)

Front 5

What are characteristics of Hb?

Back 5

Found in RBC
Constitutes 1/3 of RBC total weight
~14 g Hb in each L of blood
Each Hb molec has a heme joined to a ptn globin with 4 polypeptide chains, each with an Fe2+ that can bind 1 molec of O2

Front 6

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

Back 6

Because it combines rapidly and rversibly with O2

Front 7

Where do CO2 and O2 bind Hb?

Back 7

O2 binds heme
CO2 binds globin
.: no competition

Front 8

What happens at a PO2 of 100mm Hg?

Back 8

O2 physically dissolved in blood: 0.3 vol %
Tota amount of O2 bound to Hb: 19.5 vol %
Total amount of O2 in arterial blood: 20 vol %

Front 9

What molec of O2 contribute to the P O2?

Back 9

Only O2 disssolved in the blood contributes to P O2
(O2 bound to heme does not contribute to the P O2)

Front 10

What dos the HbO2 diss't curve determine?

Back 10

The mount of O2 carried by Hb for a given partial P of O2

Front 11

Descrivethe HbO2 diss't curve.

Back 11

-Curve is flat at high values of P O2 (at alveolar levels of O2)
-Curve is steep at low values of P O2 (at peripheral tissue levels of PO2)

Front 12

What happens at high values of PO2?

Back 12

The amount of O2 bound to Hb or HbO2 satys roughly constant (alveolar PO2 drops by 20mmHg, from 100 mmHg to 80mmHg)

Front 13

How low does the PO2 have to drop to have a significant drop in HbO2?

Back 13

PO2 has to drop down to 60mmHg

Front 14

What happens at high O2? low o2?

Back 14

High: want to bind O2
Low: want Hb to release its O2 so it can be released into the tissues

Front 15

What happens at low PO2 in the peripheral tissues?

Back 15

A small drop in PO2 unloads the O2 from Hb to the tissue

Front 16

When does HbO2--> Hb + O2?

Back 16

At lower PO2 values
*At the tissue level, PO2 can get as low as 1-3mmHg
-> drop in PO2 from 40 -> 20 mmHg can end with a drop in %HbO2 from 75% to 35%
-> drop in PO2 from 100 -> 80 mmHg can end with a drop in % HbO2 of less then 3%)
*Important in matching tissue O2 supply to tissue O2 need

Front 17

What happens as blood enters the tissue capillaries?

Back 17

Plasma PO2 > interstitial fluid PO2
O2 diffuses across the cap mb into the ISF
This lowers the plasma PO2 and O2 diffuses out of the erythrocytes into the plasma
Get diss't of HbO2-> Hb + O2 because of lowering of erythrocyte PO2

Front 18

What is the result of large amounts of O2 transfer from HbO2 to body cells?

Back 18

Goes only by passive diffusion

Front 19

What is Hb under resting conditions?

Back 19

75% saturated at the end of he tissue caps

Front 20

What substance do muscle cells have that's similar to Hb?

Back 20

Myoglobin
->intracellular carrier which facilitates the diffusion of O2 throughout the muscle cell

Front 21

What determines the affinity of Hb for O2?

Back 21

Hb's quaternary structure

Front 22

What kind of binding do Hb and O2 have?

Back 22

Cooperative binding

Front 23

How many O2 does myoglobin bind?

Back 23

1 O2 molec
-> Has a hyperbolic shape
Only releases its O2 at very low PO2

Front 24

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

Back 24

Hb concentration

Front 25

What happens under decreased Hb concentration (anaemia)?

Back 25

Even when O2 saturation is 97.5%, less O2 can be carried in the blood by Hb

Front 26

What is the Bohr Effect?

Back 26

Shift in the HbO2 diss't curve to the right when CO2 or T increases or blood pH decreases

Front 27

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

Back 27

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

Front 28

What is 2,3-DPG?
What happens when 2,3-DPG increases?

Back 28

End product of RBC metabolism
Can increase during hypoxia (due to high altitude or lung disease)
Get shift to the right when 2,3-DPG increases

Front 29

What happens when T dec, pH inc or dec in CO2?

Back 29

Opposite effect
Shift to the left
At lower PO2, have higher % saturation of Hb

Front 30

When do the Bohr effect factors have little effect on the total amount of O2 combined with Hb?

Back 30

Above 80mm Hg

Front 31

What happens when the curve shifts to the right?

Back 31

Don't hav to go to such low PO2 for Hb to release its O2

Front 32

What is carbon monoxide (CO) poisoning?

Back 32

CO has a very high affinity for the O2 binding sites in Hb (210-fold)
.: it reduces the amount of O2 bound to Hb
It also shifts the O2-Hb curve to the left, .: decreasing the unloading of O2 to the tissue (O2 now has higher affinity for Hb and won't want to come off)
-> In CO poisoning, there's little stmulation to increase ventilation because PaO2 remains normal

Front 33

What is the primary product of the oxidative processes of the body?

Back 33

CO2

Front 34

How much O2 is used and CO2 produced at rest?
How does this compare with heavy exercise?

Back 34

O2: 300ml/min
CO2: 250ml/min
Heavy exercise: these #'s can inc by 20-fold

Front 35

What are the 3 forms that CO2 is carried in?

Back 35

1) Physically dissolved in the blood (10%)
2) Combined with Hb to form HbCO2 (11%)
3)Bicarbonate (79%)

Front 36

How is CO2 physically dissolved in the blood?

Back 36

According to Henry's law, CO2 from the tissues diffuses into the plasma where it is physically dissolved

Front 37

How does CO2 combine with Hb to make HbCO2?

Back 37

CO2 combines with the globin part of Hb (no competition with O2 which binds the heme part)

Front 38

How is CO2 carried as bicarbonate?

Back 38

CO2 combines with H2O to produce carbonic acid (H2CO3)
This rxn is very slow in plasma, but as CO2 diffuses into the erythrocytes, the rxn is aided by the enzyme carbonic anhydrase (CA)

Front 39

What does carbonic anhydrase (CA) do?

Back 39

Helps CO2 combine with H2O to make H2CO3
(1) CO2 + H2O --CA--> H2CO3
(2) H2CO3 --> HCO3- + H+

Front 40

How does the cell remain neutral if HCO3- leaves an RBC?

Back 40

Cl- goes in

Front 41

What happens in the tissue caps?

Back 41

CO2 enters the RBC from the plasma
CO2 + Hb-> HbCO2
CO2 + H2O --CA-->H2CO3
H2CO3 --> H+ + HCO3- (diffuses out of cell)
Cl- enters cell to keep charge balance

Front 42

What happens in the pulmonary caps?

Back 42

Rxns occur the other way
HbCO2--> CO2 + Hb
H2CO3 --> CO2 + H2O
H+ + HCO3- --> H2CO3
HCO3- diffuses into the cell, Cl- diffuses out of the cell and CO2 diffuses out of the RBC and into the plasma

Front 43

What kind of reactions are the CO2 transport reactions?

Back 43

Reversible reactions

Front 44

What happens if CO2 production increases?

Back 44

Production of HbCO2, HCO3- and H+ increases
(like in equations 1 and 2)

Front 45

What happens when the blood PCO2 decreases?

Back 45

HCO3- goes to H2CO3
H2CO3 -> CO2 + H2O
HbCO2 -> Hb + CO2

Front 46

When is the bood PCO2 lowered?

Back 46

When venous blood flows through the lung capillaries
H+ + HCO3- --> H2CO3 --CA-->H2O + CO2 {3}
HbCO2 --> Hb + CO2 {4}

Front 47

What is the result of having higher blood PCO2 than alveolar PCO2?

Back 47

Net diffusion from the blood into the alveoli lowers the blood PCO2
**normally as fast as CO2 is generated from HCO3- and HbCO2, it diffuses into the alveoli

Front 48

What happens to free Hb in the tissue caps?
Why does this happen?

Back 48

Hb w/ot O2 can combine with H+
H+ + HbO2 <--> HHb + O2
This happens because reduced Hb is less acidic than HbO2
->Hb acts as a buffer

Front 49

What is the Haldane effect?

Back 49

Presence of reduced Hb in the tissue caps helps with the blood loading of CO2 pushing eqn 1 and 2 to the right
shift H2CO3 ---> HCO3- + H+ to the right: produce more HCO3-, best way to transport CO2

Front 50

What is the result of the Haldane effect?

Back 50

For a given PCO2, more CO2 is carried in deoxygenated blood than oxygenated blood
-> The O2 sat'n of blood influences the CO2 diss't curve by shifing it to the right
As Hb unloads O2 into the tissues, it's able to take up increased amounts of CO2 from the tissues
Haldane effect: Mixed venous blood can carry more CO2 than can arterial blood

Front 51

What is the difference between the CO2 diss't curve and the HbO2 curve?

Back 51

CO2 diss't curve has no steep or flat portions
Relationship btw CO2 content and PCO2 is almost linear
->Hypoventilation and alveolar PCO2 rises: arterial, cap , tissue and venous CO2 also rise

Front 52

What happens if the alveolar ventilation is doubled?

Back 52

Alveolar PCO2 is halved
.: an increase in alveolar ventilation proportionally increases CO2 removal

Front 53

LOOK AT DISS"T CURVES

Back 53

AFTER HALDANE EFFECT