BMS02-1006 pH & Buffering Flashcards
pH
H conc
What type of H
Free ones not bound ones
Blood pH
7.35-7.45
Living pH range
7-7.8
What is out of normal range called? (2)
Acidosis
Alkalosis
How do we get acids? (4)
Food
Protein breakdown
Incomplete ox of fat or glucose
Carbon dioxide
What regulates pH in the body? (3)
Blood buffers
Lungs
Kidneys
% of water in men, women, babies and elderly?
Babies - 73%
Elderly - 45%
Men - 60%
Women - 50%
Molar of water?
55.6M
When does pH = pKa
Half the equivelace point
pKa=
-log Ka
What is Ka
Diss constant
What is pKa?
The pH when half the acid is diss, acid = conjugate base
Strong base and excess weak acid
What does a low pKa indicate?
Strong acid
Henderson-Hasselbalch equation
pH=pKa+log(A/HA)
Buffer
Minimizes pH changes on addition of small volumes of acid or alkali
What makes a buffer
Weak acid and base
When does a buffer work best?
At its pKa therefore you know which pH it works best at
Where does the HCO3- buffer act?
Blood and saliva
What is the pKa of H2co3 to HCO3-
6.1
What is the pKa of H2PO4 - to HPO4 2-
6.8
What is H2CO3 proportional do?
pCO2
Which is the only buffering AA?
Histidine
Why don’t COOH and NH2 of AA buffer well?
COOH pKa 2.34
NH3 pKa 9.66
Why does histidine buffer in Hb?
pKa changes when its not free as neighbouring groups affect it
pKa in oxy and deoxy Hb
Oxy 6.8
Deoxy 7.8
Critical pH & value
Highest pH at which there is a net loss of mineral from the teeth
5.5
Why is it only roughly 5.5?
Solubility of enamel varies with pH as its constantly in saliva which varies in Ca and K ions at times
What does critical pH depend on?
Ionic product of CaP in saliva, which the amount of Ca decides
What does this mean?
Changed the ions concentrations means you can lower the critical pH so it doesn’t demineralise as quickly
What happens in the conc of either ions is too high?
It become destabilised and forms a ppt known as calculus
What is the stephans curve?
A way to asses carciogenicity (tooth decay causation) of different foods
What are local anaesthetics?
Weak bases
What are the 2 forms and why?
Unionised and ionised, the unionised is able to cross the membrane
