Carriage of gases Flashcards
Where is oxygen found in the body?
in alveolar gas in lungs, in solution in plasma, Majority bound to RBC, Bound to myoglobin in muscle
oxygen in solution equation
O2 in sol=pp of O2 x solubility
what is pp of O2 in aterial blood?
13.3kPa
solubility of O2 in blood
0.225ml O2 per litre of blood kPa
How much oxygen per litre of blood
13.3x0.225= 3ml litre
Total amount of O2 in arterial blood
200ml
what are our oxygen requirements at rest
250ml a minute at rest
what are our oxygen requirements during exercise
can increase upwards of 4000ml
structure of RBC
Biconcave, flexible, small, large SA to vol ratio, 7um in diameter, no nucleus so more space for Hb, contains 280million Hb molecules, Hb has 4 prosthetic groups (fe)
consists of 2 alpha and 2 beta chains in adults. it is a globular protein, is soluble
Haemoglobin+oxygen=
oxyhaemoglobin
Haemoglobin-oxygen=
deoxyhaemoglobin
equation for association
HHb+O2—-HbO2 + H+
What facilitates the affinity of O2
Concentration of CO2, when high affinity decreases, O2 is released
Binding of O2 to haem
Affinity is low, as first O2 binds leads to a change in shape, increases the affinity for 2 & 3rd bind easier, 4th takes longer as it attaches to remaining prosthetic group
Normal oxygen saturation in blood
98
Describe the Bohr effect
When the affinity for O2 is facilitated by the conc of CO2, is a sigmoid (s-shape)
PvO2
venous partial pressure of O2= 5.3kPa (40mmHg)
PaO2
arterial partial pressure of O2= 13.3kpa (100mmHg)
Factors that affect the bohr curve to right (o2 dissociation curve)
dependent on partial p of O2,
increase in temp
increases PCO2
decreased pH (due to CO2)
increased 2,3 DPG (metabolic product in RBC)
If curve shifts to right:
Hb affinity for O2 is reduced, O2 is given off to tissues where CO2 is high, Hb is less saturated
If curve shifts to left:
Hb affinity for O2 is increased, O2 is picked up at lungs
effect of CO2 on curve
increased CO2 causes more H+ concentration, reducing pH
a drop in pH shifts curve to the right, pH causes bond to weaken between Hb and O2, leading to offloading
CO2 transport in blood:
10% dissolved in plasma
15% if CO2 bound to plasma proteins
75% transported as carbonic acid
Buffering of CO2 equation
H2O+CO2-H2CO3-H++HCO3-
explain equation
CO2 diffuses into RBC
water combines with co2 to form carbonic acid, this is catalyzes by carbonic anhydrase enzyme, this causes carbonic acid to dissociate into H+ and HCO3- ions, HCO3- diffuses out of RBC, Cl- moves in to restore electrochemical balance
H+ lowers pH
Carbamino compounds
CO2 combines with Hb to form carbinohaemoglobin
H+ and CO2 can inhibit binding of O2,(Haldane effect)
Define Haldane effect:
Binding of O2 to Hb promotes release of CO2 and H+, e.g., at lungs
At tissues:
15% of CO2 replaces O2 in RBC forming carboxyhemoglobin, causes O2 to be released at tissues, causes an increase in H+, so lowers pH, leading to more O2 to be released
At Lungs:
High affinity for O2, as O2 combines with Hb to form oxyhaemoglobin, releases CO2 at lungs, allowing it to be breathed out, bicarbonate recombine with H+ to form carbonic acid which dissociates to water & CO2 which diffuses out of RBC
What are the percentage regarding CO2:
amount of CO2 dissolved in plasma
Amount of CO2 bound to Hb
Amount of CO2 transported as HCO3- ions
7% dissolved in plasma
70% carried as HCO3- ions
23% is attached to Hb to form carbinohaemoglobin
