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
