Acids, Bases and Buffers

Question 1

what are buffers important in

Answer 1

living systems

Question 2

what do buffers do

Answer 2

they maintain the pH of the body within normal pH ranges
they ensure enzymes and other cellular processes function optimally

Question 3

what are examples of inorganic buffers

Answer 3

phosphate and bicarbonate

Question 4

what is the normal pH for blood

Answer 4

7.4

Question 5

what is the normal pH range for urine

Answer 5

6

Question 6

what is the normal pH for gastric fluid

Answer 6

2

Question 7

what is the normal pH for saliva

Answer 7

6.2-7.2

Question 8

what is an example of a macromolecule in the body that can act as a buffer

Answer 8

amino acids

Question 9

are many molecules in biological systems weak acids/bases or strong acids/bases

Answer 9

weak

Question 10

what can ionic properties be influenced by

Answer 10

hydrogen ion concentration

Question 11

what are bases

Answer 11

substances that usually combine with hydrogen ions in water

Question 12

the greater the acid dissociation constant…

Answer 12

…the stronger the acid

Question 13

what is the henderson-hasselbalch equation

Answer 13

pH = pka + log10 [B-]/[A]

Question 14

how can you determine pH

Answer 14

using indicators or electrical methods like a pH meter

Question 15

how can indicators be used to determine pH

Answer 15

they show a difference of colour between their ionised and deionised form. ratio of ionised to deionised indicator is determined by pH and this ratio determines the colour of the indicator. the depth of colour of the indicator can be used to measure pH

Question 16

what is the ionised form of indicators

Answer 16

[In-]

Question 17

what is the deionised form of indicators

Answer 17

[HIn]

Question 18

what are indicators

Answer 18

weak acids that show a difference of colour when ionised which is used to determine the pH of a solution

Question 19

how much indicator is used

Answer 19

not a lot - the pH cant be altered by it this way

Question 20

why is only a small amount of indicator ever used

Answer 20

so the pH is not altered

Question 21

equationto show how the degree of dissociation and pH is related

Answer 21

pH = pKa + log10 [In-] / [HIn]

Question 22

what is the most accurate way of determining pH

Answer 22

pH meter

Question 23

are electric methods more effective at determining pH than indicators

Answer 23

yes

Question 24

how can the pH measurement be made by pH meters

Answer 24

using a glass electrode.

Question 25

what are glass electrodes

Answer 25

thin walled glass bulbs containing a platinum electrode immersed in 1M of hydrochloric acid

Question 26

what are buffer solutions

Answer 26

solutions that resist changes in pH when acid or base is added

Question 27

what do buffer solutions consist of

Answer 27

a conjugate acid-base pair of either a weak acid or a weak base

Question 28

what role do buffers play in the body

Answer 28

maintaining pH homeostasis

Question 29

what does buffering in the mouth limit

Answer 29

pH changes due to the acid produced by plaque bacteria

Question 30

how may the pH in the mouth change

Answer 30

the acid produced by the plaque bacteria

Question 31

when do buffers operate optimally

Answer 31

when they are 50% dissociated

Question 32

when is buffering most effective

Answer 32

when the concentration of the acid and the base are equal

Question 33

how do plaque bacteria produce acid

Answer 33

by fermenting dietary carbohydrate

Question 34

how does the plaque pH fall

Answer 34

production of acid from the fermentation of carbohydrates from the diet

Question 35

how is dental caries formed by plaque bacteria

Answer 35

- the bacteria ferment dietary carbohydrate to produce acid - this acid reduces the pH - this leads to increased solubility of dental enamel - this results in dental caries if not reversed

Question 36

how is the acid produced by plaque bacteria neutralised

Answer 36

the saliva acts as a buffer

Question 37

can the buffering of saliva to neutralise acid produced by plaque bacteria prevent dental caries

Answer 37

if the buffering is adequate

Question 38

what does saliva contain that aids buffering

Answer 38

proteins which are histidine rich known as histatins

Question 39

what is an important buffer in the body that can be found in such things as blood

Answer 39

bicarbonate

Question 40

what is another useful buffer that is not important physiologically

Answer 40

sodium acetate

Question 41

why is sodium acetate useful in biochemistry

Answer 41

illustrates the principle of buffering

Question 42

what is buffering capacity

Answer 42

this is the volume that can be added before there is a dramatic change in pH

Question 43

what form does histidine exist in when at a neutral pH

Answer 43

zwitterion form

Question 44

what does it mean if an amino acid is in its zwitterion form

Answer 44

both a positive and a negative charge is being carried