Gaseous diffusion and transport Flashcards
Factors affecting O2 carriage
pO2 is proportional to conc dissolved in blood. Hb
How to calculate O2 carrying capacity of normal blood
max O2 1g of Hb can combine with x normal blood Hb concentration=Oxygen capacity of normal blood
O2 saturation of blood entering pulmonary capillaries and leaving
enter=75% leave=97-100%
What is the haem group
iron porphyrin compound attached via histidine N to globin. O2 binding is oxygenation, iron remains in Fe2+ strate after O2 released
When does 2,3 DPG increase
hypoxia, anaemia
What is anaemia and what causes it
when there is reduced content of functional Hb in blood. Caused by defect Hb production or red cell numbers. O2 carrying capacity reduced
How is Hb association curve affected in anaemia? sketch
venous pO2 will be lower so tissue pO2 also low. Extraction of O2 during exercise limited
What are the negative effects of CO binding to Hb
reduces amount of O2 bound to Hb
shifts O2 binding curve to left, increases O2 affinity of remaining binding site decreasing unloading of O2
Sketch O2 dissociation curve for CO poisoning
tissues still remove 5mldl-1 of blood. Venous PO2 even lower (2kPa)=tissue PO2
HbF binds DPG more or less than HbA
less
Cyanosis what is it
If supply of O2 to tissues is deficient, content of de-oxyHb in tissue capillary increases because of hypoxia. De-oxy Hb has blue-ish tinge causing discolourisation of tissues
2 types of cyanosis
Peripheral-reduced blood flow to region resulting in hypoxic tissue causing blue-ish tinge in extremities. Cause=cardiovascualr shock, low temp, reduced CO, poor arterial supply
central=arterial hypoxaemia, buccal mucosa and lips used to spot.
Cause=chronic respiratory disease e.g. COPD (~8kPa), right to lef shunt reduces O2 sat
At which point is cyanosis observable
Arterial blood containing >1.5-2g/dl of deoxyHb, canosis is observable even in well-perfused tissues. OCcurs when O2 sat <85% if [Hb] is normal
How are CO2 carried and state the proportions
HCO3-=60%
Hb-CO2=30%
Dissolved CO2
CO2+H2OH2CO3H+ +HCO3- describe
Reaction 1: slow in plasma but fast in RBC because of presene of carbonic anhydrase
Reaction 2 aided by buffering o f {H+] by deooxy-Hb. Bicarbonate formed by reaction 2 diffuses out down its conc grad via antiporter into plasma in exchange for Cl- (chloride shift)