Acid-base balance Flashcards
Why should the pH be kept constant in the body?
Enzymes function at a particular pH within a narrow range
Enzymes have a huge number of functions around the body
Abnormal pH can result in disturbances in a wide range of body systems.
What is the result of an abnormal pH?
Abnormal respiratory and cardiac functions
Derangements in blood clotting and drug metabolism
How does the metabolism of carbohydrates and fats produce acid?
CO2 + H2O = H2CO3 (volatile acid), which is reversible with H+ and HCO3-
- CO2 doesn’t usually result in an increase in H+ in the plasma - excreted from the body via the lungs
- H2CO3 produced is known as a volatile acid.
How does protein metabolism produce acid?
Generates non-volatile (fixed) acids.
Examples:
S-containing amino acids (such as cysteine and methionine) make H2SO4
lysine, arginine and histidine make HCl
Why do non-volatile acids from metabolism need to be removed quickly?
Otherwise there will be a net gain of H+
What are the 3 mechanisms that compensate for the disturbances in body pH?
*the ICF and ECF buffering systems
*the respiratory system adjustment of ECF PCO2
*the renal adjustment of ECG [HCO3-]
What is the first line of defense against changes in body pH?
Intracellular and extracellular buffer systems.
Participate in accordance with their pKa and their quantity.
What is a particularly important buffer system? Why is it important?
CO2-HCO3- buffer system
- CO2 and HCO3-, can be regulated independantly
What is the second mechanism against changes in body pH?
Respiratory system that regulates the plasma PCO2
How does the respiratory system respond to changes in pH?
Controls the excretion or retention of metabolically produced CO2
What is the third mechanism against changes in body pH?
Kidneys
How do kidneys respond to changes in pH?
Regulates excretion or retention of HCO3-
Regulates the regeneration of HCO3-
What is a buffer?
Solution that minimises the change in [H+]
What are the advantages of the CO2-HCO3- buffering system? PART 1
CO2 and HCO3- can be regulated independently.
Excretion or retention of CO2 is controlled by the lung
Reabsorption and regeneration of HCO3- is controlled by the kidney.
