pH & Buffering Flashcards

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1
Q

What is pH?

A

A measure of hydrogen ion concentration

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2
Q

What hydrogen ions does acidity not depend on?

A

Hydrogen ions not bound to anions

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3
Q

What is the normal pH range of blood?

A

7.35-7.45

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4
Q

Where does acid in the stomach come from?

A

Some acid enter in food.
Breakdown of proteins, incomplete oxidation of fats or glucose.
Loading and transport of carbon dioxide in blood.

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5
Q

What is the acid - base balance regulated by?

A

The lungs, kidney, systems in the blood called chemical buffers

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6
Q

What do buffers do when the pH rises or falls?

A

rise - released H+

fall - binding H+

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7
Q

What molar solution is pure water?

A

55.6M solution

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8
Q

What magnitude must the concentration of hydrogen ions and hydroxide ions equal?

A

10 to the -14

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9
Q

How is pKa shown on an acid dissociation curve?

A

The straight line where buffering is occuring

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10
Q

Where can a good blood buffer, buffer at?

A

pH 7

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11
Q

What is a definition for Ka?

A

The pH at which the acid is half dissociated. There are equal amounts of undissociated acid and its conjugate base.

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12
Q

The lower the pKa, the —- the acid?

A

Stronger

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13
Q

What is the Henderson Hasselbalch equation?

A

pH = pKa + log (acid / conjugate base)

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14
Q

How does pKa relate to buffering?

A
  • Buffers are mixtures of acids and their conjugate bases
  • Buffering is the ability of a solution to resist a change in pH when acid/alkali is added
  • At the pKa, there are equal amounts of dissociated and non dissociated forms of the acid
  • At the pKa, buffering is best
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15
Q

At what pH does the alpha carboxyl and alpha amine group deprotonate?

A
carboxyl = pH 2
amine = pH 10
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16
Q

Which amino acids are the ones with can dissociate?

A

Electrically charged ones

17
Q

What makes haemoglobin a good buffer?

A

The large number of histidine residues. When oxygen is delivered, the pKa value increases

18
Q

What is critical pH?

A

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

19
Q

Why is the critical pH not an exact value?

A

The solubilty of enamel apatite varies with pH and teeth are buried in constantly replenished saliva which the concentration of calcium and phosphate ions varies.

20
Q

How could we get a tooth to withstand a lower pH before demineralising?

A

Increasing local concentrations of calcium and or phosphate

21
Q

What are all local anaesthetic agents? What two forms can the exist in?

A

Weak bases, unionised and ionised