Minimum urinary output required to excerete end products of protein metabolism is
**Core Concept**
The minimum urinary output required to excrete end products of protein metabolism is related to the concept of nitrogen balance and the body's ability to eliminate waste products of protein catabolism. This involves the renal excretion of urea, ammonia, and other nitrogenous waste products.
**Why the Correct Answer is Right**
To maintain nitrogen balance, the body must excrete a minimum amount of nitrogenous waste products, primarily urea, which is produced through the deamination of amino acids. The kidneys play a crucial role in this process, and a minimum urinary output of 500 mL/day is necessary to ensure adequate excretion of these waste products. This is because the kidneys filter a significant portion of the blood, and a minimum volume of urine is required to maintain this filtration process and prevent the accumulation of toxic waste products.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because a urinary output of 100 mL/day is too low to ensure adequate excretion of nitrogenous waste products.
* **Option B:** This option is incorrect because a urinary output of 200 mL/day is still below the minimum required for adequate excretion of nitrogenous waste products.
* **Option C:** This option is incorrect because a urinary output of 400 mL/day, while closer to the minimum required, is still not sufficient to ensure adequate excretion of nitrogenous waste products.
**Clinical Pearl / High-Yield Fact**
A minimum urinary output of 500 mL/day is a critical parameter in assessing renal function, particularly in patients with acute kidney injury or chronic kidney disease.
**Correct Answer: D. 500 mL/day**