Gas transport

Question 1

1. State Dalton’s Law.

Answer 1

Partial pressure in a gas mix is the sum of the partial pressure of each of the gases

Question 2

2. State Fick’s Law.

Answer 2

Molecules diffuse from regions of high conc to low conc in a rate proportional to the gradient, surface area and diffusion capacity of the gas, but inversely proportional to thickness

Question 3

3. State Henry’s Law.

Answer 3

At constant temp, the amount of gas that will dissolve is directly proportional to its partial pressure

Question 4

4. State Boyle’s Law.

Answer 4

Volume is inversely proportional to pressure

Question 5

5. State Charles’ Law.

Answer 5

Volume is proportional to temperature

Question 6

6. Describe how partial pressure of oxygen changes as it passes down the airways.

Answer 6

Partial pressure of o2 starts around 21.3kPa, 0Co2 and 0h20
As it goes down air gets humidified, slowed and mixed-20kPa O2, OCo2 and 6.3h20. In the resp airway, O213.5, Co2 5.3 and H2O 6.3

Question 7

7. What happens to the air as it passes down the airways?

Answer 7

It gets humidified, warmed, slower and mixed

Question 8

8. How much oxygen can be dissolved in our blood?

Answer 8

Blood cannot take much oxygen-17ml of O2 can be dissolved in ALL our blood at 0.34ml/dL. Whats needed for life is 250ml/min so not even close

Question 9

9. What is the normal oxygen consumption at rest?

Answer 9

250ml/min

Question 10

10. What is the binding capacity of oxygen to haemoglobin?

Answer 10

That why we use haemoglobin-can carry a lot more oxygen than just blood. 2% is dissolved, 98 is haemoglobin 15.1ml/dL

Question 11

12. Describe the structure of a normal variant of haemoglobin and of foetal haemoglobin.

Answer 11

Fe2+ in heam group binds 1 O2 each
Haemoglobin is a 2 alpha 2 beta tetramer-that’s haemoglobin A (HbA). Normal variant HbA2 exists with 2alpha and 2delta-2% of Hb
Foetal haemoglobin, HbF is 2 alpha and 2 gamma (trace)

Question 12

13. Explain why haemoglobin is considered an ‘allosteric’ molecule.

Answer 12

Oxygen affinity is actually low if none is bound. But as the 1st one bind, conformational change which increases affinity-and as more bind, the more the affinity increase. So low affinity for 1st one but high for the 4th one

Question 13

14. What change occurs in the middle of the haemoglobin tetramer when oxygen binds?

Answer 13

As it binds O2, space for 2,3DPG to bind appears-which reduces affinity for O2. 2,3DPG is a by product of glycolysis, so as/where ATP metabolism is high, the DPG comes in and SQUEEZE out the last few O2 molecules

Question 14

15. What is the name given to the phenomenon where oxygen binding to haemoglobin increases the affinity making more oxygen bind?

Answer 14

Cooperative bindin-results in a sigmoidal binding curve of O2 in relation to conc/pressure

Question 15

16. What would the consequences be if the oxygen dissociation curve was linear?

Answer 15

Youd get a very large saturation change/variance in the lungs, where the pressure differs-very little scope to purely load

Question 16

17. What are the benefits of having a sigmoid ODC?

Answer 16

Large variation of saturation in tissue, at low pO2. But as the pressure is high (lungs) the saturation is very high and stays all throughout the change of pressure-near 100% saturation at alveaolar pO2, but goes fro, 8% to 76% in tissue pO2

Question 17

18. What is P50?

Answer 17

The pressure at which 50% of oxygen is saturated-normally in range with tissue pO2, but can give a good idea of where the curve is (right shifted , left shifter). Normaly around 3.3kPa

Question 18

19. What conditions can shift the ODC to the right?

Answer 18

Right shift reflects a higher energy consumption-exercise. Along that happens increase in temp, acidosis, Hypercania (high CO2), increase 2,3DPG)-oxygen is dissociating MORE in tissue, so has less saturation as it exits those lower tissue pressure (around 50% vs 76% before)

Question 19

20. What conditions can shift the ODC to the left?

Answer 19

The opposite to exercise-oxygen dissociates LESS-comes out of tissue more saturated. Happens with decrease of temp, alkalosis, hypocapnia, Decrease 2,3DPG

Question 20

21. What conditions can shift the ODC upwards?

Answer 20

means you can just carry MORE oxygen-the 100% saturation now corresponds to a higher amount of O2 in blood. Due to polycynthaemia-increase of haematocrit due to increase RBC. Saturation as exit tissue the SAME, as it has still unloaded the right amount of O2

Question 21

22. What conditions can shift the ODC downwards?

Answer 21

Downwards means you can carry LESS oxygen-aneamia, or lack of Fe2+ is a common one. As you unload the same amount of O2 in tissue, saturation is the SAME

Question 22

23. How does haemoglobin saturation change in the previous two shifts (up and down) of the ODC?

Answer 22

Curve are shifter up/down but the Y axis is also adjusted-what changes isn’t the % of total, but the actual total being higher/lower

Question 23

24. How does carbon monoxide shift the ODC and why?

Answer 23

CO has much greater affinity-meaning it bind Hb better than O2. So it reduces how much O2 you can carry and the Max O2 saturation you can have. It increases affinity by cooperative binding, but decreases capacity (down and left shift)

Question 24

25. Describe the shape of the ODC of myoglobin and foetal haemoglobin and why this shape is needed for their function.

Answer 24

Myoglobin is a monomeric muscle protein with a sigmoidal binding curve. At the same pressure of O2, it is much more saturated, meaning its affinity for O2 is higher-steals it from HbA to provide muscle
Foetal haemoglobin is similar, to give O2 to child-but still sigmoidal, just higher. Higher affinity for O2 at same pressure than HbA

Question 25

26. What is the PO2 of blood arriving at the respiratory exchange surface?

Answer 25

Around 5.3 kPa-40mmHg, but its still about 70% oxygen saturation-does not arrive deoxygenated to alveoli O2 from alveoli will pass through cells-diffuse into blood and then into RBC (lower O2 so gradient), then into heamoglobin

Question 26

27. Why does the Hb saturation of the blood decrease from 100% at the respiratory exchange surface to 97% in the systemic circulation?

Answer 26

Because the blood from pulmonary circulation gets mixed back up with bronchial venous blood (lower pO2 than the one that’s just been refilled to 100%) before entering the left atrium-it becomes MIXED venous blood

Question 27

28. What are the changes in concentration of oxygen and saturation that take place at the tissues?

Answer 27

97% saturated blood with 20ml/dl O2 comes in. Oxygen flux is the amount being deposited. At that pressure, lose about -5ml/dL of blood traversed-which as there is 50dL of blood (5L), it adds up to 250 ml/min as said before

Question 28

29. Define oxygen flux and state the usual oxygen flux at rest.

Answer 28

Around -5ml/dL, so for 50dL its 250 ml/min

Question 29

30. Describe the reaction of carbon dioxide with water.

Answer 29

CO2 naturally diffused into blood from cell (down gradient)-but is more soluble than water. With water, reacts to make carbonic acid (H2CO3). This can later dissociate to HCO3- and H+ to regulate pH. All of that is slow RBC play a role by being full of carbonic andhydrase-which catalyses the CO2+water to H2CO3 and into HCO3- and H+. Then the HCO3- is moved back across

Question 30

31. Why does bica take place faster in the red blood cells?

Answer 30

RBC are full of carbonic anhydrase-CO2 diffuses in then reacts with the enzyme and water-nearly 5000x faster making carbonic acid and HCO3-. This HCO3- is then transported back out of the RBC via AE1 transporter in exchange for a Cl-, to maintain charge balance-called chloride shift

Question 31

31. Why does carbonic anhydrase reaction take place faster in the red blood cells?

Answer 31

RBC are full of carbonic anhydrase-CO2 diffuses in then reacts with the enzyme and water-nearly 5000x faster making carbonic acid and HCO3-. This HCO3- is then transported back out of the RBC via AE1 transporter in exchange for a Cl-, to maintain charge balance-called chloride shift

Question 32

32. Which transporter moves the bicarbonate produced in the red blood cell into the plasma?

Answer 32

The AE1 transporter, which exchanged 1 HCO3- for one Cl-, maintaining the charges-called the chloride shift

Question 33

33. This transporter (AE1) also allows the influx of which ion? What is the term given the this movement of ions?

Answer 33

Cl-, chloride shift

Question 34

34. What effect does the influx of chloride (antiport with bicarbonate via AE1) have on the red blood cell?

Answer 34

The Cl going in also draws water, which is being used by the carbonic anhydrase-so if not drawn would cause it to shrink

Question 35

35. How does carbon dioxide bind to proteins in the erythrocyte and what does it form?

Answer 35

Binds to the amine end of haemoglobin, making Carboaminoheamoglobin (hbCO2). And as the H+ conc increases from making HCO3-, proteins make for a good buffer of that, to reduce the pH changes

Question 36

36. What is the net CO2 flux?

Answer 36

+4ml/dL

Question 37

37. Why are total oxygen consumption and total carbon dioxide production not equal?

Answer 37

Because some water is lost in metabolic water production

Question 38

38. What is pulmonary transit time?

Answer 38

Blood only exchanges gases around the respiratory membrane, where cells are thin enough. This time is only about 0.75s. But at rest, 0.25s is all that is needed As you exercise and pulmonary blood flow increases, that gets longer-but there is enough time to reoxygenate. For CO2 it more willing to diffuse to even faster

Question 39

39. What is the Haldane effect?

Answer 39

The amount of CO2 that bind Hb changes in relation to the amount of O2 bound-if there is a lot of O2 (100% saturated, CO2 will not be able to bind the amine end. But as saturation reaches around 75% as in tissue, CO2 bind happily

Question 40

40. What is the ventilation perfusion mismatching of the lungs?

Answer 40

The blood flow and air flow is not homogenous in lungs-less blood perfuses the apex, and more perfuses the base because of the resistance of gravity Alveoli have better ventilation at top SO, top has too good ventilation for its perfusion, while bottom has great perfusion but lower ventilation