pH and buffering

Question 1

what is pH

Answer 1

measure of H ion conc

acidity or alkalinity of a solution

Question 2

what does acidity depend on

Answer 2

only on free H+ not those still bound to anions

Question 3

what is blood pH range

Answer 3

7.35 - 7.45

Question 4

what is the living blood pH range

Answer 4

7.0 - 7.8

Question 5

what is it called when blood pH too high and low

Answer 5

alkalosis and acidosis

Question 6

where do acids come from in the body?

Answer 6

• diet
• breakdown of proteins
• incomplete oxidation of fats or glucose
• loading and transport of CO2 in the blood

Question 7

how is acid-base balance regulated

Answer 7

by lungs and kidneys

and chemical buffers in the blood

Question 8

what do buffers do

Answer 8

resist abrupt and large swings in pH by
- releasing H+ when pH rises

• binding H+ when pH drops

Question 9

what happens when pH rises and pH drops in buffered solution

Answer 9

rises - OH inc

drops - H+ inc

Question 10

what % of an infant is water

Answer 10

73

Question 11

in old age what is water % of body mass

Answer 11

45

Question 12

what is water % of healthy man and woman

Answer 12

60 and 50

Question 13

why do men have a higher proportion of water than women

Answer 13

women have more fat which is anhydrous

Question 14

what M is pure water

Answer 14

55.6M

Question 15

what should a buffer contain

Answer 15

weak acid and its conjugate base

Question 16

what gives the best buffer

Answer 16

pH at half disscociation

Question 17

what is Ka

Answer 17

dissociation costan of an acid [H+][A-]/[HA]

Question 18

what does a large Ka and small pKa value mean

Answer 18

stronger the acid

Question 19

what is pKa

Answer 19

-logKa

Question 20

what is the equivalence point

Answer 20

when the two reactants are mixed un exactly the proportions indicated by the equation - equal moles

Question 21

what is the Henderson-Hasselbach equation

Answer 21

pH= pKa + log [A-]/[HA]

Question 22

what occurs at pKa

Answer 22

equal amounts of dissociated and non dissociated forms of the acid (conjugate base and acid)
- buffering is best

Question 23

what are pKa values of
H2CO3 > HCO3-
H2PO4- > HPO42-

Answer 23

6.1 and 6.8

Question 24

which amino acids are involved in physiological buffering

Answer 24

histidine

- most amino side chains do not buffer in a physiological range

Question 25

where does glycine buffer

Answer 25

2.3 and 9.6

alpha carboxyl and amino groups are not good physiological buffers

Question 26

pKa of oxyHb

Answer 26

6.8

Question 27

pKa of deoxyHb

Answer 27

7.8
changes due to orientation
neighbouring groups affect the pKa

Question 28

what is critical pH

Answer 28

the highest pH at which there is a net loss of mineral from the teeth

Question 29

what is the critical pH value

Answer 29

5.5

Question 30

what does the critical pH depend on

Answer 30

amount of Ca in the saliva

- depends on ionic product of calcium phosphate in saliva

Question 31

how can we lower critical pH so the tooth could withstand a lower H without demineralising

Answer 31

increasing local concentrations of calcium and/or phosphate

Question 32

what happens if Ca or phosphate is too high

Answer 32

calcium phosphate in the saliva or plaque fluid becomes destabilised and will precipitate out to form calcus

Question 33

what is Stephan’s curve

Answer 33

assesses cariogenicity of different food