Physiology 4 - O2 transport Flashcards
how is O2 picked up in the lungs?
where is it transported to and for what use?
O2 is picked up in the lungs BY the BLOOD.
It is transported to the TISSUES for CELLULAR USE.
where is CO2 produced?
how is it transported?
where is it transported to and why?
CO2 is produced in the tissues.
transported by the blood.
transported to the lungs fo removal from the body.
what does Henry’s Law state?
the amount of a gas dissolved in a liquid (e.g. blood) at a constant temperature is
proportional to the partial pressure of the gas in equilibrium with the liquid.
for each mmHg of PaO2, how many ml of O2 are dissolved per litre of blood.
3ml of O2 per litre of blood at PO2 of 13.3kPa
if the cardiac output is at its normal of 5L/min, what would the oxygen delivery to tissues be?
15ml/min of oxygen delivery
what is the resting tissue oxygen consumption requirement at rest?
250ml/min is the requirement
give 2 ways in which O2 can be transported in the blood?
1) as free dissolved oxygen (PaO2) inn the blood plasma
2) as oxyhemoglobin in red blood cells (O2 bound to haemoglobin in red blood cells)
how many molecules of oxygen can each haemoglobin molecule carry?
each haemoglobin caries 4 OXYGEN MOLECULES.
is the binding of oxygen to haemoglobin reversible or irreversible?
REVERSIBLE
how many sub-units does haemoglobin have?
it contains 4 sub-units
what do each of these sub-units contain?
a NON-PROTEIN HAEM GROUP
what happens when oxygen binds to the haemoglobin sub-units?
it causes a CONFORMATIONAL CHANGE in the protein, altering the relationship with other protein sub-units & therefore the affinity of the haemoglobin molecule for oxygen
whats the name given to the process where the binding of oxygen alters the affinity of haemoglobin for oxygen?
co-operativity
when is haemoglobin considered fully saturated?
when haemoglobin is carrying its maximum O2 load
what is the primary factor which determines the percent saturation of haemoglobin with O2?
PO2
after oxygen has bound to haemoglobin and it has reached the tissues.
In what 4 conditions are optimum to cause the release of oxygen from haemoglobin? i.e. what factors will shift the oxygen-haemoglobin curve to the right?
1) low PaO2 or high PaCO2
2) low pH
3) high temperature
4) high levels of 2-3 Diphosphoglycerate (DPG) in red blood cells
what is the written formula for oxygen delivery index?
DO2I
what is the equation for calculating the oxygen delivery index (DO2I)?
and what do each of the components mean?
DO2I = CaO2 x CI
CaO2 = oxygen content of arterial blood CI = cardiac index (relates cardiac output to body surface area)
what is the equation to calculate the oxygen content to arterial blood (CaO2)?
and what do each of the components mean?
CaO2 = 1.34 x [Hb] x SaO2
1.34 = one gram of haemoglobin can carry 1.34ml of O2 when fully saturated
[Hb] = haemoglobin concentration
SaO2 = % Hb saturated with O2
what 4 factors can impair oxygen delivery to tissues?
1) respiratory disease
= decreased PO2, hence decreased Hb saturation with O2 & O2 content of blood
2) heart failure
3) anaemia
- decreased Hb concentration, decreased O2 content of blood
4) decreased partial pressure of inspired oxygen
what is the name of the curve to describe oxygen binding to haemoglobin?
SIGMOIDAL curve.
= binding of one O2 to haemoglobin increases the affinity of haemoglobin for O2 UNTIL all the haemoglobin molecules are fully saturated.
Then the curve flattens.
what does the flat upper portion and steep lower portion of the sigmoidal curve mean?
flat upper = a moderate fall in alveolar PO2 will not much affect oxygen loading
steep lower = peripheral tissues get a lot of oxygen for a small drop in capillary PO2
what effect does the Bohr effect have on the oxygen-haemoglobin curve?
it shifts the curve to the right
why does the Bohr effect shift the curve to the right?
it increase the concentration of CO2, deceasing the pH, resulting in a lower affinity of haemoglobin for O2
describe the molecules contained within adult haemoglobin & foetal haemoglobin.
ADULT haemoglobin
- 2 alpha & 2 beta proteins
FOETAL haemoglobin
- 2 alpha & 2 gamma sub-units
does foetal haemoglobin interact more or less with 2,3-biphosphoglycerat and why?
- interacts LESS
- because, foetal haemoglobin has HIGHER AFFINITY FOR O2 compared to adult haemoglobin
- allows O2 to transfer from mother to foetus even is the PO2 is low
in what 2 muscles is myoglobin present?
skeletal & cardiac muscles
how many haem groups does each myoglobin molecule have?
1 haem group
describe the oxygen-haemoglobin curve for myoglobin.
HYPERBOLIC
in what conditions does myoglobin provide a short term storage for O2?
anaerobic conditions
in what muscle state would you expect to find myoglobin?
damaged muscle
