Biochemistry Of Buffers

Question 1

What is a buffer and it’s role?

Answer 1

A buffer is a moelcule that resists PH changes which occur by additions of acid or base to the system
- they cannot completely stop PH from changing but reduce the change in PH that would otherwise occur in their absence
- They are usually mixture of weak acids and their conjugate bases

Question 2

What is water?

Answer 2

• polar molecule
  -dissolves most charged molecules
  -constitutes about 70% of mass of most living things

Question 3

What forms the basis of Sorensen PH scale

Answer 3

Question 4

What is the Ka for acetic acid

Answer 4

Ka = [ H+] [CH3COO-] / [CH3COOH]

Question 5

What is the rule of buffer titration graphs?

Answer 5

• PH = pKa at plateau points on titration graph
  -number of plateau points on titration graph depends on number of protons of acid
• buffering regions extend about 1 PH unit either side of pKa value

Question 6

What is intracelluar PH buffered by?

Answer 6

Phosphate and histidine side chains of proteins

Question 7

What is extra cellular PH buffered by?

Answer 7

Bicarbonate buffer system in blood serum

Question 8

Where is the carbon dioxide generated dissolved in

Answer 8

Blood plasma

Question 9

What is there an equilibrium between in serum?

Answer 9

Equilibrium between carbon dioxide water and carbonic acid

Another equilibrium between carbonic acid and bicarbonate

Question 10

What does Le Chaterliers principle predict in saliva

Answer 10

Acid removing hydroxide and phosphate can drive more HAP into solution which can dissolve the teeth

Question 11

What are the 3 buffer systems in saliva?

Answer 11

Bicarbonate- stimulated saliva
Phophaste
Protein

Question 12

What enzyme is present in saliva and increased buffering system

Answer 12

Carbonic anhydride can catalyse uptake of protons to bicarbonate

Question 13

What happens with increased salivary flow rate?

Answer 13

PH INCREASES
Bicarbonate concentration increase
Buffering capacity increases due to an increase in plaque acid conc

Question 14

How is plaque acid produced and how is it prevented?

Answer 14

Produced by ferment dietary carbohydrates
But mechanical stimulation/ mastication can increase salivary flow rate
This can increase washing action to remove fermentsble food and acidic food

Question 15

What does the STEPHAN CURVE PRESENT

Answer 15

PH against time after carbohydrate consumption
With and without saliva
Min PH 6:5 with saliva
5:5 without saliva

Question 16

What does mastication increase?

Answer 16

Salivary flow
Which increases secretion of carbonic anhydride VI which catalysts uptake of acidic protons to bicarbonate
This preceding dissolution of enamel

Question 17

What are the effects of compromised salivary buffering on oral health?

Answer 17

Reduce salivary flow rate, less washing of fermentable carbohydrates and less removal of acidic foods/drinks

This acid causes dissolution of enamel by removing hydroxyl and phosphates ions form HAP

Less carbonic anhydride secreted and hence less catalysis of reaction between protons and bicarbonates to form carbonic acid and carbon dioxide