gas transport Flashcards
what is partial pressure?
sum of all the partial pressures of a gas must be equal to total pressure
what is the formula for partial pressure of gas?
fraction of gas in gas mixture x barometric pressure
what are the 2 ways oxygen is transported?
dissolved and bound to haemoglobin
how much O2 in blood is in dissolved form?
a small %
how is dissolved O2 measured clinically?
in arterial blood sample PaO2
why is haemoglobin required?
transport of O2 in dissolved form is not adequate
what is haemoglobin?
a major transport molecules for O2 found in RBC’s
what is the structure of Hb?
4 heme groups joined to globin protein, 2 alpha, 2 beta chains, each heme contains iron in ferrous form- site of O2 binding
why does binding and dissociation of O2 occur in milliseconds to facilitate transport?
RBC’s are only in capillaries for 1 second
is O2 binding in Hb reversible?
yes
what is the consequence of a drop in PO2 from 100-60mmHg
minimal effect on Hb saturation
what is the consequence of a small change in PO2 under 60
a large amount of O2 is released from Hb, facilitating release into tissues
how many O2 atoms can each Hb bind?
up to 4
what does O2 saturation mean?
the amount of O2 bound to Hb relative to the maximal amount that can bind
how is O2 saturation measured?
pulse oximeters- measures ratio of absorption of red and infrared light by oxyHb and deoxyHb
