REB 26. Nitrogen Excretion, Urine Composition + Analysis

Question 1

What is the most abundant gas in our atmosphere?

Answer 1

nitrogen - N2 (78%)

Question 2

Why is nitrogen a fundamental component of the building blocks of life?

Answer 2

• amino acids
• proteins
• DNA/RNA

Question 3

How is nitrogen taken into the body in the diet?

Answer 3

• must undergo fixation by bacteria
• – fixation = reduction of N2 and nitrates (changed into NH3 and ammonia)
• then taken into the body in the diet

Question 4

What is urea important for?

Answer 4

urea is important in controlling urinary volume

Question 5

How is nitrogen turnover normally balanced?

Answer 5

intake = excretion

Question 6

What is positive nitrogen balance?

Answer 6

nitrogen intake is greater than excretion

— body protein is increasing (e.g. pregnancy, growth)

Question 7

What is negative nitrogen balance?

Answer 7

nitrogen excretion is greater than intake

— “catabolic state” - using body protein for energy (e.g. malnutrition, burns, cancer)

Question 8

What is nitrogen excretion dependent on?

Answer 8

[1] Protein Intake
—- nitrogen = around 16% of dietary protein

[2] Protein Synthesis
—- body growth/muscle building

[3] Protein Catabolism

• — inadequate caloric intake (malnutrition)
• — injury
• — cancer
• — immobilization

[4] Renal Function

• — 85% of N excreted as urea, 5% as NH4+, 10% as uric acid and creatinine
• — nitrogen also lost in feces, skin exudates