| What is the concentration of H+ at pH of 7.4 | 40 nmol/litre |
| Where is hydrogen carbonate reabsorbed mainly | 80% of it is reabsorbed in the PCT
Using the mechanism of Na+/H+ exchanger 3 |
| What is basically the mechanism that hydrogen carbonate is reabsorbed | First carbonic anhydrase II breaks H+ and HCO3- inside the cell, then there is an exchange of H+ being secreted and Na+ being reabsorbed
H+ then reacts with HCO3- in the lumen to form H2CO3 where membrane bound carbonic anhydrase IV to facilitate the formation of H20 and CO2
This then enters the cell where using carbonic anhydrase II it forms HCO3- and H+ and the cycle restarts
HCO3- then leaves the cell into the blood via the 3HCO3--Na+ symporter |
| If there was an increase in HCO3- concentration or a decrease in pCO2, what would happen | the ratio to increase and cause the pH to increase → alkalosis |
| What would happen if a drop in HCO3- or a increase in pCO2 | would cause the ratio to decrease and pH to decrease leading to acidosis |
| What are the 2 mechanisms to buffer the excess H+ to maintain adequate H+ secretion in the nephron | Reaction with ammonia to form ammonium ( 60% )
Reaction of H+ with dibasic phosphate (HPO4 2-) to form monobasic phosphate (HPO4 - ) |
| How do you calculate the anion gap | [Na+ ] – ([Cl- ] + [HCO3 - ]) |
| Metabolic acidosis with high anion gap indicates what | Due to increased organic acids in the bloodstream e.g. lactic acidosis, diabetic keto acidosis |
| What does a normal anion gap indicate | This is due to loss of HCO3-
The kidneys compensate for this loss by secreting chloride so the serum remains electroneutral
Bicarbonate loss can be due to renal tubular acidosis and diarrhoea |
| What does acidosis lead to in ECF [K+] | Increase drive of K+ out of cells
Also leads to less K+ to be excreted
Can lead to hyperkalaemia |
| What can alkolosis lead to in ECF [K+] | More K+ to enter the cells
More K+ to be excreted by the kidneys
Can lead to hypokalaemia |
| When a person ingests potassium, what are the cellular events | K+ is absorbed
Insulin is secreted
K+ moves into the cells
Some H+ moves out but due to extra HCO3- in the stomach, remains neutral
No hyperkalaemia |
| In a person with diabetic ketoacidosis, what are the cellular events | No insulin --> cells produce ketones and less K+ enters the cells
ECF H+ rises, then H+ enters the cells and K+ leaves
But due to osmotic diuresis, excess electrolytes are lost hence ECF K+ does not rise
Once you give insulin, K+ moves back into the cells and ketone production is reduced
Without insulin, there is a risk of hypokalaemia |
