Acid-base

Question 1

Alkalosis:

• pH?
• CNS symptoms?
• Cause?

Answer 1

• pH > 7.45
• Drowsy, headache, convulsions
• Vomiting

Question 2

Acidosis:

• pH
• Symptoms
• Cause?

Answer 2

• pH < 7.35
• drowsy, respiratory disfunction, coma
• Diarrhea

Question 3

pH of urine

Answer 3

4.5-8 (diet dependent)

Question 4

pH of gastric acid

Answer 4

1

Question 5

pH of pancreatic fluid

Answer 5

7.8

Question 6

pH of blood/ECF

Answer 6

7.4 (tightly regulated b/w 7.35 - 7.45)

Question 7

pH of cell

Answer 7

7.1

Question 8

Why regulate pH?

Answer 8

1. Influences pH activity
2. Regulates ion transport
3. Needed for cell growth, metabolism, DNA synthesis
4. CNS (alkalosis + acidosis)

Question 9

Sources of H+ gain

Answer 9

• Generation of H+ from CO2 (hypoventilation)
• Production of non-volatile acids
• Loss of bicarbonate (i.e. diarrhoea, urine)

Question 10

Sources of H+ loss

Answer 10

• Using H+ in the metabolism of anions
• Vomit
• Urine
• Hyperventilation

Question 11

What reaction occurs in the body when CO2 is produced by cells? (with the help of which enzyme)

Answer 11

CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-

First reaction requires carbonic anhydrase

Question 12

How is H+ buffered in transit?

How is it removed from the lungs?

Answer 12

• Haemoglobin
• Takes up H+ produced in cells (HHb)
• Releases H+ in lungs (O2Hb-)
  The H+ in the lungs then goes on to form CO2

Question 13

Why do we need to breathe at a continuous rate?

Answer 13

To prevent hypo-/hyperventilation and thus acidosis/alkalosis

Question 14

What are the 3 main buffering mechanisms in the body?

Answer 14

1. Bicarbonate
2. Protein
3. Phosphate

Question 15

How does the kidney handle bicarbonate?

Answer 15

1. Reabsorption of filtered HCO3-
2. Replacement of HCO3- consumed in excretion of non-volatile acids
3. Excretion of excess HCO3-

Question 16

How is filtered bicarbonate reabsorbed in the body?

Answer 16

1. Carbonic anhydrase catalyses the formation of carbonate from CO2 and H2O in the epithelial cells
2. The carbonate dissociates into H+ ion and bicarbonate
3. The bicarbonate is absorbed into the interstitial fluid
4. The H+ ions are secreted into the lumen (coupled with Na+)
5. The H+ ions combine with bicarbonate in the filtrate to form carbonate, which is secreted as H2O and CO2
   Note: no new bicarbonate is formed

Question 17

How is bicarbonate replaced?

Answer 17

1. Carbonic anhydrase catalyses the formation of carbonate from CO2 and H2O in the epithelial cells
2. The carbonate dissociates into H+ ion and bicarbonate
3. The bicarbonate is absorbed into the interstitial fluid
4. The H+ ions combine with filtered non-volatile acids (anions), e.g. (HPO4)2-
5. The acid is excreted e.g. H2PO4-

Question 18

What is compensation? (In terms of body pH balance)

Answer 18

If one variable changes, you can get the pH back to normal by changing the other variable to restore the ratio to 20:1

Question 19

What are the 2 respiratory disturbances?

Answer 19

1. Excess CO2
   - Hypoventilation
   - Acidosis
2. Not enough CO2
   - Hyperventilation
   - Alkalosis

Question 20

What are the 2 metabolic disturbances?

Answer 20

1. Excess bicarbonate
   - Acid shortage
   - Alkalosis
2. Not enough bicarbonate
   - Excess acid
   - Acidosis

Question 21

What is the Henderson-Hasselbalch equation? (in terms of the body)

Answer 21

pH = 6.1 + log(conc. of bicarbonate / (0.03xpCO2))

Question 22

What is the ratio of bicarbonate to (0.03 x pCO2)?

Answer 22

20:1