Acid-Basics 1: Intro to pH basics and buffer systems (AS lecture)

Question 1

what is the pH range of systemic arterial blood and what is the “normal” pH

Answer 1

• 7.35-7.45
• normal = 7.4

Question 2

what is acidosis, what can this manifest as physiologically in the CNS and what can this lead to?

Answer 2

• acidosis: blood pH lower than 7.35
• manifests as depression of the CNS due to depression of synaptic transmission
• can lead to comas

Question 3

what is alkalosis, and can it lead it physiologically in the PNS and CNS and what 3 ways can this manifest in patients?

Answer 3

• alkalosis: blood pH above 7.45
• leads to overexcitability of the PNS and then CNS through facilitation of synaptic transmission

This can manifest as:
- spasms
- convulsion
- death

Question 4

pH

define pH in a sentence

Answer 4

pH is the power of Hydrogen

Question 5

what are the 2 equations for pH

Answer 5

pH = -log10([H+])

OR

pH = log10(1/[H+]

where:

• [H+] is concentration of Hydrogen ions

Question 6

what is the equation for the hydration of CO2

Answer 6

CO2 + H2O (enzyme: carbonic anhydrase) <—> H2CO3 <—> H+ + HCO3-

Question 7

what are 3 ways metabolism produces acid and give 1 example of each

Answer 7

1. Carbonic acid (volatile acid production):
   - Example: hydration of CO2 which happens when we breathe
2. non-volatile acids (nutrient breakdown):
   - example: protein metabolism
3. organic acids from intermediate metabolism:
   - example: lactic acid

Question 8

how much carbonic acid and non volatile acid is produced everyday

Answer 8

Carbonic acid: 13000 mmol/day

non-volatile acid: 50-80 mmol/day

Question 9

what are 3 lines of defence against pH disorders (abnormal pH change)

Answer 9

1. chemical buffers
2. adjusting ventilation to change PaCO2
3. kidneys adjusting renal acid or alkali excretion

Question 10

give 4 examples of chemical buffers

Answer 10

• albumin
• haemoglobin
• carbonic acid
• phosphates

Question 11

how much of the way does adjusting ventilation to change PaCO2 restore pH to normal levels

Answer 11

restores pH 50-75% of the way

Question 12

what type of regulation is the kidneys adjusting renal acid or alkali excretion?

Answer 12

long term reguation

Question 13

how long does each line of defence against pH disorders take?

Answer 13

chemical buffers:
- fractions of a second

adjusting ventilation:
- minutes

adjusting renal acid/alkali excretion:
- hrs/days

Question 14

what is the drawback to haemoglobin as a chemical buffer?

Answer 14

it is limited in quantity

Question 15

what is the drawback of the phosphate chemical buffer system

Answer 15

it is limited in quantity

Question 16

what are 2 advantages of the Bicarbonate buffer system over the other extracellular buffer systems

Answer 16

• easily regulated
• highly abundant

Question 17

what are the 3 main extracellular buffer systems

Answer 17

• protein buffer system
• phosphate buffer system
• carbonic acid-bicarbonate buffer system

Question 18

what is the main extracellular buffer system

Answer 18

• carbonic acid-bicarbonate buffer system