🥼 acids, bases & buffers Flashcards
What is an acid?
A molecule or ion which tends to give up protons in solution (proton donor).
Examples include carbonic acid, lactic acid, and hydrochloric acid.
What is carbonic acid?
An acid formed when CO2 dissolves in blood tissue fluids, which acts as a buffer at physiological pH.
What is lactic acid?
An acid formed by human cells from glucose during anaerobic respiration which causes cramps.
It is converted to glucose by glucogenesis in the liver.
What is hydrochloric acid?
An acid secreted into the stomach as part of the digestive process.
What is a base?
A molecule or ion which tends to gain protons in solution (proton acceptor).
Examples include hydroxyl ion, acetate ion, ammonia, and amines.
What does the Henderson Hasselbach equation indicate?
Stronger A/B → greater Ka/Kb → smaller pKa/pKb.
How do acids affect calcium phosphate dissolution?
Increase in [H+] shifts equilibrium right, increasing solubilisation of calcium phosphate.
Soft drinks have low pH, causing tooth erosion; fruit juices with organic acids bind to Ca++, contributing to tooth erosion.
What happens when there is an increase in [Ca] or [PO4]?
Equilibrium shifts left, inhibiting solubilisation and promoting remineralisation.
Saliva contains Ca & PO4, aiding remineralisation; calcium-containing foods like milk protect teeth from decay.
What is a buffer?
A solution that can neutralise small amounts of added acid or base, maintaining the pH of the solution.
It is made of a weak acid and its conjugate base, or a weak base and its conjugate acid.
What is the main buffer in saliva?
Bicarbonate (HCO3-) which comes partly from blood & carbonic anhydrase (H2CO3-) that dissociates to H+ & bicarbonate.
Phosphate & proteins also contribute to saliva’s buffering capacity.
How does phosphate act as a buffer?
It acts as a buffer at three different pH ranges, since three equilibria are involved.
What are proteins?
Large biomolecules & macromolecules that contain side chains which can be acidic or basic.
Histidine is an example, important for buffering capacity in saliva against the effect of acids.
What are histatins?
A class of proteins in saliva which are rich in histidine and help buffer saliva against the effect of acids.
