The Significance of pH Flashcards
What is the function of buffers?
Maintain pH of body within normal pH ranges, ensure enzymes and other cellular processes function optimally
What are the two types of buffers?
Inorganic (phosphate and bicarbonate) and macromolecules (amino acid side chains)
What are the ionic properties of acids and bases influenced by?
Hydrogen ion concentration
What is the equation for pH?
pH=-log10[H+]
What happens when acids dissociate?
Release hydrogen ions
What is an acid?
Substance which in water tends to produce hydrogen ions
What is a base?
Substance which in water tends to combine with hydrogen ions
What is an equilibrium reaction made up of?
Hydrogen ion donor (acid) and an acceptor (base)
What does the equilibrium ensure?
That the concentrations of hydrogen ions and base ions is constant to acid ions
What is the acid dissociation constant equation?
Ka = [H+][B-]/[A]
What is the Henderson-Hasselbalch equation?
pH=pKa + log10[B-]/[A] where pKa = -log10Ka
What happens when H+ increases?
Ka also increases
What happens when the acid is stronger?
The Ka is larger and the pKa is smaller
What equation shows the degree of dissociation?
pH = pKa + log10 [In-]/[HIn]
How is the ratio of [In-]/[HIn] determined?
It is determined by the pH
What methods can be used to determine pH?
Indicators and electrical methods e.g. pH meters
What is the action of oral buffers?
Limit pH changes due to acid production by plaque bacteria
When is buffering most effective?
When [A]=[B-] or when half dissociated (at their pKa)
What does saliva do?
Saliva acts as a buffer and neutralises the acid produced preventing dental caries
What are the important buffers in saliva?
Bicarbonate, histatins due to histidine content
What does plaque bacteria do?
ferment dietary carbohydrate to produce acid causing plaque pH to fall leading to increases solubility of dental enamel which results in dental caries
