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respiration > Gas transport > Flashcards

Gas transport Flashcards

1
Q
  1. State Dalton’s Law.
A

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

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2
Q
  1. State Fick’s Law.
A

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

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3
Q
  1. State Henry’s Law.
A

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

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4
Q
  1. State Boyle’s Law.
A

Volume is inversely proportional to pressure

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5
Q
  1. State Charles’ Law.
A

Volume is proportional to temperature

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

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

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

It gets humidified, warmed, slower and mixed

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

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

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9
Q
  1. What is the normal oxygen consumption at rest?
A

250ml/min

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

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

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11
Q
  1. Describe the structure of a normal variant of haemoglobin and of foetal haemoglobin.
A

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)

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12
Q
  1. Explain why haemoglobin is considered an ‘allosteric’ molecule.
A

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

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13
Q
  1. What change occurs in the middle of the haemoglobin tetramer when oxygen binds?
A

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

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14
Q
  1. What is the name given to the phenomenon where oxygen binding to haemoglobin increases the affinity making more oxygen bind?
A

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

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15
Q
  1. What would the consequences be if the oxygen dissociation curve was linear?
A

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

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16
Q
  1. What are the benefits of having a sigmoid ODC?
A

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

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17
Q
  1. What is P50?
A

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

18
Q
  1. What conditions can shift the ODC to the right?
A

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)

19
Q
  1. What conditions can shift the ODC to the left?
A

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

20
Q
  1. What conditions can shift the ODC upwards?
A

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

21
Q
  1. What conditions can shift the ODC downwards?
A

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

22
Q
  1. How does haemoglobin saturation change in the previous two shifts (up and down) of the ODC?
A

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

23
Q
  1. How does carbon monoxide shift the ODC and why?
A

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)

24
Q
  1. Describe the shape of the ODC of myoglobin and foetal haemoglobin and why this shape is needed for their function.
A

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

25
Q
  1. What is the PO2 of blood arriving at the respiratory exchange surface?
A

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

26
Q
  1. Why does the Hb saturation of the blood decrease from 100% at the respiratory exchange surface to 97% in the systemic circulation?
A

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

27
Q
  1. What are the changes in concentration of oxygen and saturation that take place at the tissues?
A

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

28
Q
  1. Define oxygen flux and state the usual oxygen flux at rest.
A

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

29
Q
  1. Describe the reaction of carbon dioxide with water.
A

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

30
Q
  1. Why does bica take place faster in the red blood cells?
A

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

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

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

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

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

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

Cl-, chloride shift

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

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

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

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

36
Q
  1. What is the net CO2 flux?
A

+4ml/dL

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

Because some water is lost in metabolic water production

38
Q
  1. What is pulmonary transit time?
A

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

39
Q
  1. What is the Haldane effect?
A

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

40
Q
  1. What is the ventilation perfusion mismatching of the lungs?
A

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

respiration (15 decks)

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