11 + 12 - Acid and Base

Question 1

What is a buffer

Answer 1

solution that can resist pH change upon the addition of an acid or a base. Able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.

Question 2

What makes up a buffer

Answer 2

Consist of a weak acid and the salt of that acid functioning as a weak base

Question 3

Where is HCO3- reabsorbed mainly

Answer 3

PCT

Question 4

What do alpha intercalated cells excrete (DT)

Answer 4

secretes acid, absorbs bicarb

Question 5

What do beta intercalated cells excrete and absorb

Answer 5

Secrete bicarb

absorb acid

Question 6

What is the cause of metabolic alkalosis

Answer 6

Increased bicarb production/reduced excretion

Decreased production of H+ or excretion of H

Question 7

Causes of H+ loss

Answer 7

Low chloride - Diuretics which inhibit chloride resorption
= Volume depletion results in secondary hyperaldosteronism as a result there is increased exchange of sodium for K and H, K depletion further promotes H excretion
Low K+
= Hyperaldosterone
= Liquorice
= Barters, liddles, gitelmans

Question 8

Causes of alkali intake

Answer 8

Milk/alkali syndrome

Bicarb therapy

Question 9

Cause of metabolic acidosis

Answer 9

an excess of hydrogen ions, can result either from an excess production of hydrogen ions, a loss of bicarbonate/ failure to regenerate bicarbonate in the kidney.
o ‘metabolic acidosis’.

Question 10

Normal anion gap

Answer 10

12-16

12 if K+ excluded

Question 11

Raised anion gap acidosis

Answer 11

o Bicarbonate goes down

o Increase in unmeasured anion

Question 12

Causes of increased anion gap

Answer 12

o	Methanol intoxication
o	Uremia
o	Isoniazid or Iron overdose
o	Salicylate intoxication	
o	Ketoacidosis		
o	Methanol
o	Aldehyde (paraldehyde)
o	Lactate

Question 13

Normal anion gap acidosis

Answer 13

o Chloride increases but bicarb decreases because chloride is swapped for bicarb via an antiport

Question 14

Renal causes of normal gap acidosis

Answer 14

 Renal Tubular Acidosis (cannot excrete H+)

 Carbonic anhydrase inhibitors

Question 15

GI causes of normal anion acidosis

Answer 15

 Severe diarrhoea (loss of bicarb)
 Uretero-enterostomy or Obstructed ileal conduit
 Small bowel fistula

Question 16

Other causes of normal anion gap acidosi

Answer 16

 Losses via NG tube
 Villous adenoma
 Recovery from DKA
• Ketone anions secreted as potassium/sodium salts
• Chloride ions retained to maintain electrical neutrality

Question 17

Low gap acidosis

Answer 17

 Decrease in Unmeasured anion (e.g. loss of albumin)
• Haemorrhage
• Liver cirrhosis
• Nephrotic syndrome.

Question 18

In PCT

CA and bicarb ting (draw it out)

Answer 18

• In the lumen, CA converts H+ and bicarbonate into carbonic acid, the pumping out of the hydrogen atoms via Na/H pump pushes the equation to the left producing H2O and CO2.
• Water and carbon dioxide diffuses into the cell where the equation to the right is favoured as the H+ is constantly being pumped out
• The water and carbon dioxide form carbonic acid which then breaks down into bicarb and acid. The bicarb cannot leave through the lumen so it is pumped into the interstitium via the Na+/HCO3¬¬¬-

Question 19

Normal pH

Answer 19

7.35 to 7.45

Question 20

• Formation of H+ from cellular metabolism

Answer 20

o Acids produced during the breakdown of foods (esp. proteins)- 60 mmol/d
o CO2 metabolically produced and form carbonic acid with H2O- 15 mol/d,
o Acids resulting from other metabolic activity e.g. lactic acid in exercise- 1.5 mol/d
o In disease state, even more ketoacids

Question 21

Methanol poisoning forms what acid

Answer 21

formic acid

Question 22

Ethylene glycol forms what acid

Answer 22

Glycolic acid + oxalic acid

Question 23

CO poisoning, drugs form what acid

Answer 23

Lactic acid

Question 24

How does acidaemia lead to hyperkalaemia

Answer 24

tissues release K+ from within the cells
o Potassium swapped and replaced by the H+ and in order to maintain electroneutrality.
 H+ taken up by cells to reduce serum H+.