What percentage of plasma does urea represent, commonly tested for renal function?

Urea is a waste product formed from the breakdown of proteins and is commonly assessed to evaluate renal function. In the context of plasma composition, urea represents a relatively small percentage compared to the overall components in plasma. The correct answer is significant because it highlights that urea constitutes about 45% of the total nitrogenous waste in the plasma, although the entire plasma makes up approximately 7% of the total body weight.

This understanding is crucial for interpreting renal function tests. The concentration of urea in the plasma can indicate how well the kidneys are filtering waste products from the blood. A higher concentration might suggest impaired renal function, while a lower concentration could indicate good kidney health or various physiological states.

In contrast, the other percentages provided do not accurately reflect the typical concentration of urea in the plasma. The options that suggest a higher percentage, such as 30%, 60%, or 75%, misrepresents the average plasma urea levels observed in healthy individuals, which is why they are not suitable answers for this question.