Maintenance of pH

Question 1

kW equation

Answer 1

Kw = [H+][OH-] = 10^-14 M^2

Question 2

Acid and base ion concentration changes

Answer 2

• Acids [H+] increases and [OH-] decreases•

- Bases:[H+] decreases and [OH-] increases

Question 3

pH equation

Answer 3

pH = -log10 [H+]

Question 4

Physiological cell pH range

Answer 4

5-7.6

Question 5

What acids and bases fully dissociate in water

Answer 5

Strong

Question 6

What do weak acids/bases do in solution?

Answer 6

Partially dissociate

Question 7

HA equation

Answer 7

HA < = > H+ + A-

Question 8

Ka equation

Answer 8

Ka = [H+] [A-] / [HA]

Question 9

Equation that links pH with conjugate acid/base conc

Answer 9

pH = pK + log ([conjugate base] / [conjugate acid])

Question 10

Stomach pH

Answer 10

1-3

Question 11

Plasma pH

Answer 11

7.4

Question 12

Pancreatic juice pH

Answer 12

8.8

Question 13

How can pH be regulated

Answer 13

Partitioning and buffering

Question 14

How is pH regulated through partitioning?

Answer 14

Add a proton pump (Protons can’t cross membranes alone)

Question 15

How is pH regulated through buffering?

Answer 15

H+ + Buffer ⬄ Buffer-H+

Question 16

What is carbonic anhydrase?

Answer 16

• Major buffer of the body

- Acts in circulation and in tissues

Question 17

What is normal blood pH and what pH’s indicates acidosis?

Answer 17

Normal blood pH = 7.4, Acidosis pH = 7.35

Question 18

What pH can lead to death?

Answer 18

pH around 7

Question 19

Clinical markers of pH?

Answer 19

• [HCO-3] = 24 mM (pH 7.4) compared to 9.4 mM (pH 7.03)•

- [CO2] = 1.2 mM (pH 7.4) compared to 1.1 mM (pH 7.03)

Question 20

How is a reduction in [HCO^-3] in the blood significant?

Answer 20

• less HCO^-3 available for buffering

- If more HCO^-3is lost, none is available for additional buffering tasks

Question 21

What determines the extent of drug dissociation?

Answer 21

pH

Question 22

What does pK determine with drug administration

Answer 22

the fluid in which to administer drug and the volume administered - influences the concentration of ionised or unionised drug in solution and whether drug will remain in solution or precipitate

Question 23

Where are weak acid/base drugs secreted into?

Answer 23

Actively secreted into the renal tubule and rapidly excreted

Question 24

Equation linking pH, pKA and acid dissociation conc

Answer 24

pH = pKa + log ([A-]/[HA])

Question 25

What does pKa determine?

Answer 25

pKa determines population of undissociated (HA) and dissociated species (A-) at any pH

Question 26

What is Phenolbarbtol?

Answer 26

• Stabilises nerve membranes preventing signal conduction

- pK = 7.4

Question 27

What is Phenytoin?

Answer 27

• Intravenous administration to treat severe seizures

- pK =8.1