Lab 5 - Renal Function and Acid-Base Balance

Question 1

What are the two principle routes of acid excretion?

Answer 1

Lungs (as CO2 and H2O)

Kidneys

Question 2

What are the three forms that H+ takes in the urine?

Answer 2

1. Free H+
2. Attached to phosphate (Na2HPO4, NaH2PO4)
3. Attached to ammonia (NH3, NH4+)

Question 3

What is the pH of normal glomerular filtrate?

Answer 3

7.4

Question 4

What factors can affect the acidity of the urine? i.e. acid excretion

Answer 4

Diet
Renal disease
Exercise

Question 5

What causes a meat-eaters diet to be more acidic?

Answer 5

High amounts of animal protein
Contains sulphur containing amino acids
Sulphur is converted into sulphuric acid

Question 6

What causes a vegetarian diet to be more alkaline?

Answer 6

Contains less proteins

Contains salts of carboxylic acids (e.g. sodium citrate) which are converted into sodium carbonate which is alkali

Question 7

What is the total amount of H+ produced each day?

Answer 7

60-70nmoles

Question 8

What is the normal reference range for blood H+ concentration?

Answer 8

35-45 nmoles/l

Question 9

What H+ concentrations are incompatible with life?

Answer 9

Greater than 120 nmol/l

Less than 20 nmol/l

Question 10

Why are buffers created for the excretion of H+?

Answer 10

Because there is a limit to the H+ concentration gradient that can be generated so using buffers keeps the H+ lower than expected

Question 11

How much H+ is excreted in urine per day?

Answer 11

60-70 mmoles

Most as titratable acidity and NH4+

Question 12

What is the immediate source of NH4+ and where and how is it synthesised?

Answer 12

In the kidney, glutamine is broken down by glutaminase into glutamate and NH3+

NH3 then reacts with H+ in tubule cells and is excreted into the filtrate as NH4+