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Molecules and Cells > Acids, Bases and Buffers > Flashcards

Acids, Bases and Buffers Flashcards

1
Q

what are buffers important in

A

living systems

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2
Q

what do buffers do

A

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

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3
Q

what are examples of inorganic buffers

A

phosphate and bicarbonate

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4
Q

what is the normal pH for blood

A

7.4

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5
Q

what is the normal pH range for urine

A

6

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6
Q

what is the normal pH for gastric fluid

A

2

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7
Q

what is the normal pH for saliva

A

6.2-7.2

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8
Q

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

A

amino acids

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9
Q

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

A

weak

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10
Q

what can ionic properties be influenced by

A

hydrogen ion concentration

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11
Q

what are bases

A

substances that usually combine with hydrogen ions in water

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12
Q

the greater the acid dissociation constant…

A

…the stronger the acid

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13
Q

what is the henderson-hasselbalch equation

A

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

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14
Q

how can you determine pH

A

using indicators or electrical methods like a pH meter

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15
Q

how can indicators be used to determine pH

A

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

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16
Q

what is the ionised form of indicators

A

[In-]

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17
Q

what is the deionised form of indicators

A

[HIn]

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18
Q

what are indicators

A

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

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19
Q

how much indicator is used

A

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

20
Q

why is only a small amount of indicator ever used

A

so the pH is not altered

21
Q

equationto show how the degree of dissociation and pH is related

A

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

22
Q

what is the most accurate way of determining pH

A

pH meter

23
Q

are electric methods more effective at determining pH than indicators

A

yes

24
Q

how can the pH measurement be made by pH meters

A

using a glass electrode.

25
Q

what are glass electrodes

A

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

26
Q

what are buffer solutions

A

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

27
Q

what do buffer solutions consist of

A

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

28
Q

what role do buffers play in the body

A

maintaining pH homeostasis

29
Q

what does buffering in the mouth limit

A

pH changes due to the acid produced by plaque bacteria

30
Q

how may the pH in the mouth change

A

the acid produced by the plaque bacteria

31
Q

when do buffers operate optimally

A

when they are 50% dissociated

32
Q

when is buffering most effective

A

when the concentration of the acid and the base are equal

33
Q

how do plaque bacteria produce acid

A

by fermenting dietary carbohydrate

34
Q

how does the plaque pH fall

A

production of acid from the fermentation of carbohydrates from the diet

35
Q

how is dental caries formed by plaque bacteria

A
  • 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
36
Q

how is the acid produced by plaque bacteria neutralised

A

the saliva acts as a buffer

37
Q

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

A

if the buffering is adequate

38
Q

what does saliva contain that aids buffering

A

proteins which are histidine rich known as histatins

39
Q

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

A

bicarbonate

40
Q

what is another useful buffer that is not important physiologically

A

sodium acetate

41
Q

why is sodium acetate useful in biochemistry

A

illustrates the principle of buffering

42
Q

what is buffering capacity

A

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

43
Q

what form does histidine exist in when at a neutral pH

A

zwitterion form

44
Q

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

A

both a positive and a negative charge is being carried

45
Q
A

Molecules and Cells (13 decks)

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