Oxygen Transport in Blood Flashcards
What is Dalton’s Law of partial pressure?
Each gas in a mixture of gases exerts a pressure that is proportional to its conc. and independent of other gases present
What can partial pressure exerted by a single gas be calculated as?
PO2 = PB.FO2
In air PB = 760mmHg
FO2 = 0.21 (fraction of oxygen in the air)
What is maximum partial pressure of water a function of?
Temperature
At 37 degrees = 47mmHg
What is partial pressure of oxygen in a room with humidified air?
(760 - 47) X 0.21 = 149.7mmHg
What does total amount of O2 in solution depend on?
Solubility of O2 in solution
What is Henry’s Law?
Amount of gas dissolved in a solution is directly proportional to partial pressure of the gas in the solution
Conc gas = S.gas
How is O2 transferred?
By passive diffusion
What 3 things is the rate of gas transfer proportional to?
Tissue surface area
Difference in gas partial pressure between 2 sides
Diffusion constant (solubility)
What is the rate of gas transfer inversely proportional to?
Tissue thickness
What are the two ways oxygen can be transported?
Dissolved in physical solution - 3%
Bound to Haemoglobin - 97%
What is dissolved O2 a linear function of?
PO2 (Henry’s Law)
0.003ml O2/100ml blood for each mmHg PO2
What type of molecule is Heme?
Iron-porphyrin compound
Describe structure of Heme?
Joined to protein globin
Tetramer with 4 polypeptide chains - 2 alpha and 2 beta
4 haem groups, each bound to alpha or beta
What does each haem group contain?
Porphyrin ring and a ferrous atom (Fe++) - bind reversibly with O2
What bonds do deoxyHb globin chains have?
Electrostatic bonds in T conformation = low O2 affinity
What does binding of O2 to deoxyHb cause?
Breaks bonds - exposes O2 binding sites - relaxed conformation
What does R conformation have?
High affinity for O2
What is unique to Hb F (foetal)?
Profound oxygen affinity
What is the difference in Hb S (Sickle cell anemia)?
Valine instead of glutamic acid in beta chains - low oxygen affinity
What is the haemoglobin type for a normal adult?
Hb A
What 4 things affect the affinity of haemoglobin for oxygen?
pH, PCO2, 2,3DPG and temperature
What causes the oxygen-dissociation curve to shift left?
Decreased temp, 2,3-DPG H+
CO
Drop in saturation
What causes the oxygen-dissociation curve to shift to the right?
Increased temp, 2,3-DPG and increased H+
Reduced affinity at cellular level
What happens when Hb has a greater affinity for CO2?
Causes O2 to be released from haemoglobin
What does CO cause?
Reduces the oxygen carrying capacity of blood
Define oxygen capacity.
Max. amount of O2 that can be combined with Hb
1.39 ml O2/g Hb - 15g of Hb/100ml in normal blood
What is O2 saturation of Hb given by?
(O2 combined with Hb/ O2 capacity) X 100
What causes anaemia?
Reduced Hb - less than 15g/100ml of blood
