Acid-Base Homeostasis

Question 1

1. What is the normal range of the pH of arterial blood?

Answer 1

7.35 - 7.45

Question 2

2. What systems neutralise acidic and alkaline components to maintain body pH

Answer 2

Body buffering systems

Question 3

3. Define acidosis

Answer 3

Shift to acidic arterial pH

Question 4

4. Define alkalosis

Answer 4

Shift to alkaline arterial pH

Question 5

6. What is an example of a cellular activity that generates acids and give its equation

Answer 5

• Carbohydrate metabolism generates CO2 and H2O
• CO2 + H2O –> H2CO3 –> H+ + HCO3-

Question 6

7. What type of acid is CO2 regarded as?

Answer 6

a volatile acid

Question 7

8. What are acids not generated from CO2 called?

Answer 7

non-volatile acids

Question 8

9. What type of metabolism generates non-volatile acid

Answer 8

amino acid metabolism

Question 9

1. What acid is created when cysteine and methionine are metabolized?

Answer 9

sulphuric acid

Question 10

11. What acid is created when lysine, arginine and histidine is metabolized?

Answer 10

hydrochloric acid

Question 11

12. What does meat ingestion produce more of than HCO3- can neutralise?

Answer 11

more acid than HCO3- can neutralise

Question 12

13. What system is the most effective in the regulation of pH in the body?

Answer 12

Kidneys

Question 13

14. How long do chemical buffers take to regulate the pH of the body and give examples of chemical buffers

Answer 13

• seconds
• examples: Bicarbonate, Inorganic Phosphate, Proteins

Question 14

15. How long does respiration take to regulate pH of the body and how does respiration regulate it

Answer 14

• Minutes
• Hyperventilation removes CO2 and decreases free H+

Question 15

16. How long do the kidneys take to regulate the pH of the body and how do they do it?

Answer 15

• Hours to days
• do it through:

1. H+ excretion
2. HCO3- reabsorption/ excretion

Question 16

what are 3 ways body pH is renally regulated

Answer 16

1. secretion of H+ ions by the PCT, DCT and CD using a H+ ATPase pump
   2.Replace filtered HCO3-
2. Manufacture HCO3- in an amount equal to the amount used as a buffer

Question 17

what urinary buffers along the PCT and DCT buffer free H+ surrounding them

Answer 17

phosphate and ammonia urinary buffers

Question 18

what is the average pH of urine and what is a chemical feature of urine

Answer 18

• 6.0
• usually HCO3- free

Question 19

what happens at the same time H+ is secreted and what does this allow?

Answer 19

a new HCO3- is added to the blood plasma as H+ is secreted.

• this allows the normal pH to be restored

Question 20

18. What are the 3 fundamental mechanisms that allow the kidneys to regulate extracellular fluid H+ concentration?

Answer 20

1. secrete H+ ions
2. Replace filtered HCO3-
3. Manufacture HCO3-

Question 21

19. What two types of cell line the distal convoluted tubule and collecting duct

Answer 21

1. Principle cells
2. Intercalated cells

Question 22

20. Give 2 features of the principal cells and 2 features of the intercalated cells

Answer 22

Principal Cells:
- Short microvilli
- Maintain sodium / water balance

Intercalated cells:
- Extensive microvilli
- pH balance

Question 23

21. What percentage of bicarbonate reabsorption and H+ secretion occurs in the proximal tubule

Answer 23

80 to 90 percent