significance of pH Flashcards
1
Q
what are buffers?
A
- Important in living systems
- Maintain pH of body within normal pH ranges:
- blood 7.4
- urine 6.0 (range 4.4 to 8.0)
- gastric fluid 2.0
- saliva 6.2 to 7.2
- Ensure enzymes and other cellular processes function optimally
- Inorganic: phosphate (buffer reserve in skeleton), bicarbonate (major buffer)
- Macromolecules: e.g. amino acid side chains in proteins
2
Q
what is the formula for calculating pH if you have hydrogen ion concentration?
A
pH= -log10 [H+]
3
Q
what is an acid?
A
a substance which produces H+ ions when in solution (hydrogen donor)
4
Q
what is a base?
A
a substance when in solution combines with H+ ions (hydrogen acceptor)
5
Q
what is the acid dissociation constant Ka?
A
- For the dissociation of an acid, the forward reaction is balanced by the reverse reaction
- An equilibrium is established such that the ratio of the concentrations of H+ and B- to A is constant:
Ka = [H+] [B-] / [A]
- The stronger the acid, the greater is Ka and the more reaction is pushed to the right (dissociated)
6
Q
what is a pH indicator?
A
- Weak acids or bases which in the ionsied form (In-) and unionised form (HIn) show a difference in colour:
HIn ↔ H+ + In-
colourless red
The degree of dissociation and pH will be related by the equation:
pH = pKa + log10 [In-] / [HIn]
7
Q
what are the buffers in saliva?
A
bicarbonate, phosphate and histidine-rich proteins called histatins
