Question 3: Consider a simplified metabolic model to describe nitrogen metabolis

Question

Question 3: Consider a simplified metabolic model to describe nitrogen metabolism in the body. Nitrogen is ingested in the food (F), a fraction of which is actually absorbed (A), the remainder being lost in the feces (W). The absorbed nitrogen is taken up by the muscle to make protein. At small fraction of the stored muscle protein undergoes degradation and the liberated nitrogen (L) is released from the muscle. Of the liberated nitrogen, a fraction is recycled back to the muscle (R), while the rest is lost to excretion (E) in the urine. Gut Muscle If the nitrogen ingested in food is 100 g/day, but only 80% of the food is actually absorbed, while the rest goes to waste, what is the amount of nitrogen lost by excretion? Assume steady-state. Of the nitrogen liberated from muscle, 90% is excreted, while the rest is recycled, what fraction of the nitrogen entering the muscle is from the absorbed food? (In other words, what is the ratio A/(A+R)). Again, assume steady-state a) b)

Explanation / Answer

a) Absorbed nitrogen = 80% of 100 g = 100*(80/100) = 80 g/day

Absorbed nitrogen = 80 g/day

Amount of nitrogen lost = Nitrogen ingested - absorbed nitrogen = 100 - 80 = 20 g/day

Amount of nitrogen lost = 20 g/day

b) Assume all the nitrogen ingested is liberated from muscle. So 80g of nitrogen is liberated.

Excreted nitrogen from liberated nitrogen = 90% of 80g = 80*(90/100) = 72g

Recycled nitrogen = nitrogen is liberated - Excreted nitrogen = 80-72 = 8g

Fraction of nitrogen entering the muscle = 80/(80+8) = 80/88 = 0.909

Fraction of nitrogen entering the muscle = 0.909

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.