Acids, Bases and Buffers

Question 1

What is an acid?

Answer 1

A molecule or ion which tends to give up protons in solution

Question 2

What does the hydrogen ion exist as in water?

Answer 2

the hydronium ion

Question 3

What is a base?

Answer 3

a molecule or ion which tends to acquire protons in solution

Question 4

Name some important acids in biology

Answer 4

Carbonic acid, lactic acid and hydrochloric acid

Question 5

What are the acids produced by oral bacteria?

Answer 5

Lactic acid, formic acid, acetic acid, propionic acid, butyric acid

Question 6

What do acids produced by oral bacteria cause?

Answer 6

Tooth decay

Question 7

What does an increase in hydrogen ions cause in the dissolution of calcium phosphate?

Answer 7

Equilibrium shifts right and increases the solubilisation of calcium phosphate

Question 8

What does an increase in calcium/phosphate cause in the dissolution of calcium phosphate?

Answer 8

Equilibrium shifts left and inhibits solubilisation and promotes re-mineralisation

Question 9

What do calcium and phosphate do in saliva?

Answer 9

aids remineralisation

Question 10

What is tooth erosion caused by?

Answer 10

the direct effect of acids in the diet on the teeth

Question 11

What does a chelating agent do?

Answer 11

Bind to divalent and trivalent cations - bind to calcium ions which can then no longer counteract calcium solubilisation

Question 12

What acids act as chelating agents and where do they come from?

Answer 12

Organic acids which come from fruit juices

Question 13

How can buffers be made?

Answer 13

Either neutralising an acid with hydroxyl ions or mixing together a solution of acid and one of its salts with an appropriate dissolution constant

Question 14

when is a buffer at its maximum buffering capacity?

Answer 14

when it is 50% dissociated

Question 15

What is an example of a weak base and one of its salts?

Answer 15

ammonia and ammonium chloride

Question 16

What is the main buffer in saliva?

Answer 16

Bicarbonate

Question 17

What are the 3 buffers in saliva?

Answer 17

Bicarbonate, phosphate and protein

Question 18

Where does bicarbonate come from?

Answer 18

The blood and carbonic acid dissociation

Question 19

what is special about phosphate as a buffer?

Answer 19

It buffers at 3 different pH’s

Question 20

What proteins does saliva contain?

Answer 20

Histatins

Question 21

What is important about histatins?

Answer 21

They are histidine rich and therefore help to buffer the saliva against the effect of acids