If the Tm for a particular amino acid is 120 mg/100 ml and the concentration of that amino acid in the blood is 230 mg/100 ml, the amino acid will ________.
A) be actively secreted into the filtrate
B) be completely reabsorbed by the tubule cells
C) appear in the urine
D) be completely reabsorbed by secondary active transport

Question

Quizplus · Accepted Answer

When the concentration of a substance in the blood exceeds its transport maximum (Tm), the excess amount of the substance will not be reabsorbed and will appear in the urine. Therefore, in this case, the amino acid will appear in the urine as its concentration (230 mg/100 ml) is above its Tm (120 mg/100 ml). Choice A and D are incorrect as they imply active or secondary active transport, which requires reabsorption. Choice B is incorrect as it implies the complete reabsorption of the amino acid, which is not possible when its concentration exceeds its Tm.

If the Tm for a Particular Amino Acid Is 120