Respiratory strand: Lecture 6 - Carriage of O2 and CO2 in Blood Flashcards
What are the two ways in which oxygen is carried?
- Dissolved in blood
2. Combined with haemoglobin
How are amount of gas in solution and temperature related?
They’re proportional - more dissolves at low temperatures
Volume of O2 = k x PO2
How do we calculate oxygen saturation? (SO2)
SO2 = HbO2/ (HHb + HbO2)
where HHb is de-oxygenated Hb and HbO2 is Oxygenated Hb
Explain the 4 levels of structure in haemoglobin
Primary - just under 150 amino acids per chain
Secondary - globular structure
Tertiary - ‘crevice’ of haemoglobin and O2 binding
Quaternary - 4 chains (HbA = 2 x alpha and 2 x B)
Explain what one Hb molecule carries/ can carry?
4x globin chains
4x haem groups
4x iron atoms
binds 4x O2 molecules
Where is the O2 binding site for haem?
In a crevice
image slide 5
What is the R (relaxed) state?
When O2 can access binding site
What is the T (tense) state?
O2 pushed out from crevice
Why is the Hb-O2 dissociation curve a sigmoid curve?
Shape due to ‘cooperativity’ between chains
Which way does the curve shift when the pH increases?
to the left
Which way does the curve shift when the temperature increases?
to the right
What is thalassaemia?
When there is an absent globin chain
e.g alpha thalassaemia - cannot produce alpha chains. This is much more fatal than B thalassaemia as alpha chains are present in adult and foetal haemoglobin
What is HbS (sickle cell disease)?
- defective globin chain
- single amino acid defect
- red cells sickle at low PO2
What condition is caused by a defective Fe atom? (Fe3+)
Methaemoglobin
- drug induced
- metHb does not carry oxygen
What condition is caused by the wrong ligand?
CO Hb - Co BLOCKS o2 binding site
Smoking / house fires
What is the definition of a buffer?
A buffer is a solution that can minimise changes in the free H+ concentration and therefore in pH
How does a weak acid dissociate?
acid —> H+ + base
What are the 3 ways that CO2 is carried in the blood?
- Dissolved in blood
- temperature dependent - Carbamino compounds
- bound to R-NH2 groups on proteins
- includes terminal amino group and side chains of lysine and arginine - As carbonic acid/ bicarbonate
What is the equation for the formation and breakdown of carbonic acid?
formation: CO2 + H2O —-> H2CO3
breakdown: H2CO3 —> H+ + HCO3-
What is the Haldane effect?
The ability of deoxygenated blood to carry more CO2 than oxygenated blood
What does a CO2 dissociation curve look like for oxygenated and deoxygenated blood?
Image slide 14
What is the Henderson-Hasselbalch equation?
pH = pK + log10 [A-]/
[HA]
which system controls the amount of CO2?
the respiratory system
which system controls the bicarbonate concentration?
the kidneys
