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Respiratory BS > Respiratory lecture 6-Carriage of O2 +CO2 in the blood > Flashcards

Respiratory lecture 6-Carriage of O2 +CO2 in the blood Flashcards

1
Q

How is oxygen carried in the blood?

A

It is carried in two forms

  1. Dissolved in blood
  2. Bound to haemoglobin(facilitated gas transport)
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2
Q

What is the amount of gas dissolved in solution proportional to?

A

Temperature

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3
Q

At what temperature does more gas dissolve in solution?

A

At low temperature

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4
Q

what is the equation of partial pressure?

A

PP = fractional conc. x pressure

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5
Q

How to calculate partial pressure of oxygen?

A

PO2 = FiO2 x PB
=0.21 x 101.3
=21 kPa

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6
Q

How to calculate volume of O2 for blood at 37 degrees celcius?

A

Volume of O2 (ml.dl-1) =constant factor (ml.dl-1.kPa-1) x Po2 (kPa)

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7
Q

What the actual equation for volume of O2 in blood at 37 degrees?

A

0.29 ml.dl-1 = 0.0232 ml.dl-1.kPa-1 x 12.5 kPa

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8
Q

How to calculate oxygen saturation?

A

proportion of oxygenated haemoglobin divided by total haemoglobin present

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9
Q

Equation for Oxygen saturation?

A

So2= HbO2/HHb +HbO2

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10
Q

What is HHb?

A

De-oxy haemoglobin

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11
Q

What is HbO2?

A

Pxy haemoglobin

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12
Q

Equation for volume of O2?

A

Volume O2 (ml.dl-1) = SO2 (%/100) x [Hb] (g.dl-1)x 1.39(ml.g-1)

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13
Q

What is Hb?

A

Hb conc (amount of haemoglobin present)

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14
Q

What is hufner constant?

A

the number of ml of oxygen that 1 gram of haemoglobin can bind.
Theoretical amount that haemoglobin can bind.

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15
Q

What is haemoglobin primary structure?

A

141-146 amino acids per chain

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16
Q

What is haemoglobin secondary structure?

A

globular structure

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17
Q

What is haemoglobin tertiary structure?

A

‘crevice’ for haem and O2 binding

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18
Q

What is haemoglobin quaternary structure?

A

4 chains (HbA = 2 x a and 2 x b)

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19
Q

What does one Hb molecule contain?

A 
4 x globin chains
4 x haem groups
4 x iron atoms
and binds
4 x O2 molecules
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20
Q

Where is O2 binding site to haem?

A

In a crevice

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21
Q

When is Hb in relaxed form?

A

When O2 can access binding site (all four oxygen attached)

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22
Q

When is Hb in tense form?

A

When no O2 molecules are attached.

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23
Q

What happens as each oxygen binds?

A

affinity for oxygen increases which is an example of cooperativity

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24
Q

How does O2 bind to tense Hb?

A

when there is an abundance of O2 and one molecule manages to bind to a haem.

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25
Q

Why do we only use 25% of the O2 in our blood?

A

The last O2 just hops on and off as this is most efficient. Although there are more O2 molecules, they get progressively harder to access as they are bound tightly to haemoglbin

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26
Q

what shape is Hb-O2 dissociation curve?

A

sigmoid

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27
Q

Why is the shape of Hb-O2 dissociation curve sigmoid?

A

Due to cooperativity between chains

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28
Q

What are the three points on the sigmoid curve?

A

P50, Venous blood, Arterial blood

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29
Q

What is PO2 and SO2 of arterial blood?

A

12.5 kPa, 97%

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30
Q

What is PO2 and SO2 of venous blood?

A

6.3 kPa, 75%

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31
Q

What is PO2 and SO2 of P50?

A

3.5 kPa, 50%

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32
Q

Why does sigmoid shape change?

A

Due to different circumstances a left or right shift occurs

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33
Q

What changes the sigmoid shape?

A

Temperature
pH change (Bohr effect)
2,3 diphospho-glycerate in red cell

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34
Q

What does P50 determine?

A

Whether left or right shift occurs

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35
Q

What does P50 quantify?

A

where the curve is

36
Q

What happens when your blood is at :
high temp
low pH
high 2,3 dpg

A

usually caused by anaemia will make curve shift to right

37
Q

Why do those factors affect left and right shifT?

A

Due to how haemoglobin behaves. Interactions between oxygen and protein chains means at different conditions proteins behave differently.

38
Q

What happens to the haemoglobin for shift to happen?

A

Binding changes because of molecular interactions within a molecule

39
Q

Why is haemoglobin abnormal in Thalassaemia?

A

Globin chain is absent

40
Q

Why is haemoglobin abnormal in HbS (sickle cell)?

A

Defective globin chain (single amino acid defect).

Valine instead of glutamic acid (position 6)

41
Q

Why is haemoglobin abnormal in Methaemoglobin?

A

Defective Fe atom (drug induced; metHb doesn’t carry oxygen)

42
Q

What happens in CO Hb?

A

Wrong ligand (CO blocks O2 binding site)

43
Q

What is Thalassaemia?

A

Genetically inherited inability to produce a globin chain (either beta or alpha).
Alpha is more unsurvivable, as alpah form is present in all froms of Hb. Alpha chain is more critical chain.
In Beta, you can produce alpha chains and in order to replacce beta gamma and delta chains are formed.

44
Q

What happens in HbS?

A

When short of O2 or dehydrated Hb stick together and crystallise which makes red cell change shape into sickle shape. They can clump and block blood vessel=lack of blood supply which is painful.

45
Q

How to treat HbS?

A

Give them drugs which encourage HbF levels

46
Q

What happens in Methaemoglobin?

A

Fe2+ changes to Fe3+ = metHb

47
Q

what is a buffer?

A

A solution that can minimise changes in the free H+ concentration and therefore in pH

48
Q

Equation for weak acid and its base in equilibrium?

A

acid H+ + base

e.g H2CO3 H+ +HCO3-

49
Q

what happens when pH increases?

A

increase in H+ conc means decrease in pH

50
Q

What are the most common blood buffer systems?

A

Bicarbonate, plasma proteins, haemoglobin, phosphate

51
Q

What to blood buffer systems include?

A

proteins, carboxyl and amino groups at each end of the chain and basic/acidic side chains of amino acids.

52
Q

What is blood pH?

A

7.35-7.45

53
Q

What is h+ conc?

A

34-45 nmol.l-1

54
Q

How is CO2 carried in the blood?

A
  1. Dissolved in blood
  2. Carbamino compounds
  3. As carbonic acid/bicarbonate
55
Q

Is CO2 more soluble in liquid than oxygen?

A

yes 3ml dissolves at 37 degrees, 10 times as much CO2 dissolved in blood than O2

56
Q

How does CO2 bind to carbamino compounds?

A

Bound to R-NH2 groups on proteins
Includes terminal amino group and side chains of lysine and arginine
= 4ml CO2 per dl of blood is bound to protein

57
Q

How much of CO2 dissolved in blood is in carbonic acid/bicarbonate form?

A

45 ml CO2 per dl of blood

58
Q

equation for when water dissolves in blood?

A

CO2 + H2O H2CO3 H+ +HCO 3-

59
Q

what is 1st phase of co2 dissolving in water catalysed by?

A

carbonic anhydrase

60
Q

What are H+ ions buffered by?

A

Hb which has high buffering capacity

61
Q

what exchanges bicarbonate for chloride?

A

protein in red cell wall pumps it out in exchange for a chloride ion.

62
Q

what is the exchange process from bicarbonate to chloride ions called?

A

Hamburger shift

63
Q

What is the haldane effect?

A

deoxygenated blood carries more CO2 than oxygenated blood

64
Q

What happens when Hb loses its O2 going through capillary?

A

It changes the molecule that make it into a better buffer and better carbamino carriage of the CO2

65
Q

What happens when Hb loses its O2 going through capillary?

A

As it gives up O2 it gets better at carrying CO2

66
Q

What happens when Hb loses its CO2 back in the lungs?

A

It gets better at carrying O2

67
Q

What is the law of mass action rearranges, assuming all CO2 is converted into H2CO3?

A

pH (H+ conc) is proportional to a constant (6.1) + ratio of bicarb to CO2 levels

68
Q

What is pH affected by?

A

Bicarb and CO2

69
Q

What are 4 things that can go wrong according to Henderson-Hasselbalch equation?

A

too much bicarb
too little bicarb
too much CO2
too little CO2

70
Q

Why does pH rise (alkolotic)?

A

too much bicarb

decrease CO2

71
Q

what makes pH decrease (acidosis)?

A

decrease bicarb

increase CO2

72
Q

what system causes PCO2 abnormalities?

A

Respiratory system

73
Q

Why is Respiratory system responsible for PCO2 abnormalities?

A

Respiratory system is responsible for getting rid of CO2 from metabolism. When you get either acidosis or alkailosis and its caused by CO2 its referred to as either respiratory acidosis and respiratory alkilosis.

74
Q

what causes problems with non CO2 based acids in your body?

A

Renal doesn’t excrete acid or too much you will get change in bicarb level (independent of CO2. pH = acidotic or alkilotic.

75
Q

what do you call problems with non CO2 based acids in your body?

A

Renal/metabolic acidosis and renal/metabolic alkilosis

76
Q

What happens when you get an abnormality of metabolic nature?

A

Breathing changes and CO2 level changes to try to get pH level back to normal.

77
Q

How are respiratory and renal systems related when there are acid base problems?

A

Compensation for acid base problems

78
Q

what are indications of respiratory alkalosis?

A

low Pco2 and normal HCO3-

79
Q

what causes respiratory alkalosis ?

A

Hyperventilation (anxiety, iatrogenic). Too much CO2 breathed out.

80
Q

What are indications metabolic alkalosis?

A

normal pCO2, high HCO3-

81
Q

what causes metabollic alkalosis ?

A

Loss of H+ eg vomiting, abuse of antacid remedies

82
Q

What are indications respiratory acidosis?

A

high Pco2 and high HCO3-

83
Q

what causes respiratory acidosis?

A

Ventilatory failure

84
Q

What do high bicarbonate levels indicate?

A

When kidneys try to compensate by retaining bicarbonate

85
Q

What are indications metabolic acidosis?

A

low HCO3-, low PCO2

86
Q

what causes metabolic acidosis?

A

Renal failure; diabetic ketoacidosis; shock (poor tissue perfusion)

Respiratory BS (3 decks)

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