o2 and co2 carriage in blood

Question 1

law of mass action (substrates + products)
- what happens when a reaction is at equilibrium
- what happens when equilibrium disturbed
- how is equilibrium restored

Answer 1

• Rate of reaction in forward direction equals rate of reaction in reverse direction so ratio of substrates and products constant
• Rate of reaction in forward direction increases because added substrate is converted into product
• when substrates used up and reduce

Question 2

dissolved oxygen in blood is not enough
- what is conc of o2 in water and blood when po2 is at equilibrium in water and air
- how much o2 would that supply per min at rest
- what is resting rate of o2 consumption

Answer 2

• PO2 in air and water is equal. Low O2 solubility means that concentrations much lower in liquid = to 3ml / L of blood when po2 is 100 mmHg
• supply 15 ml/min at a Q of 5 L/min (at rest)
• is ~ 250 ml/min. (so it cannot support life)

Question 3

haemoglobin carrying
- what does hb do and where is it
- how is it formed and how it works
- how hb adapts to different states
- how hb maintains pressure gradient for o2 diffusion into blood from alveoli
- what happens to hb in hypoxic conditions

Answer 3

• an oxygen binding protein contained within the red blood cells
• each contains four polypeptide chains (globins), and four haeme groups, with a Fe2+ atom in the centre of each that binds to oxygen
• hb in t state (difficult) so needs high po2 in blood, when an o2 binds to hb it causes a shape change therefore hb is in R state (easy) and 3 more O2 bind with ease forming oxyhaemoglobin.
• o2 bound to hb doesn’t contribute to po2 in blood, so more o2 diffuses in and more binds to hb until equilibrium
• low po2 disturbs oxyhaemoglobin so hb has reduced affinity for o2 causing dissociation into blood then to tissues

Question 4

the difference hb makes
- when o2 normal in blood without hb
- when o2 normal in blood with hb
- when o2 low and hb normal
- anemia

Answer 4

• alveoli po2 equal in alveoli and plasma and carrying capacity is 3 ml/L blood
• alveoli po2 equal to plasma but hb maintained constant diffusion gradient and carrying capacity is 200 ml/L blood
• plasma o2 content is low so rbcs don’t reach max o2 load
• body doesn’t produce enough hb due to lack of iron so lower o2 content of rbcs and total carrying capacity falls

Question 5

oxyhaemoglobin curve
- what shape is it
- what does it mean
- shift to the left and right and factors affecting

Answer 5

• a sigmoidal shape
• o2 associates at higher po2 in lungs, 02 dissociates at lower po2 (at tissues) for metabolic processes
• Shift to left increases affinity to o2 so less o2 disscaites at lower po2 (lower acidity, less co2, no dpg (affinity for o2 so strong, hb doesn’t dissociated so suffocate) cold temp)
• Shift to right (bohr effect), decreases affinity so more 02 dissociates at higher po2 (higher acidity, higher co2, added dpg (concentrated in tissues), higher temp)

Question 6

carbon dioxide transport
- 3 ways its transported

Answer 6

• when Co2 at equilibrium, more dissolves (comp to o2) because is more soluble than o2 so plays important part of transport.(approx 7% of total)
• Around 70% carried in form of bicarbonate ions HCO3- due to the reactionn of co2 wth water forming carbonic acid which dissociates into h+ ions and bicarbonate ions (HCO3-)
• Around 23% co2 carried by hb- when associated called carbaminohaemoglobin (use empty binding sites)

Question 7

why does hb bind to hydrogen ions that are produced when carbonic acid breaks down?

Answer 7

• hydrogen ions create acidic enviro which denatures enzymes reducing rate of metabolism.
• prevents acidosis in normal conditions and respiratory acidosis during over elevated levels of co2