AAMC Exam 3, Biological Sciences

[SKaminski]

Hey, this post will pertain to questions 193:

Relevant text from passage:

Plasma clearance is affected by the tubular transport maximum (Tm) of a substance. The Tm is the maximum rate of transport (mg/min) at which a substance can be reabsorbed by the kidney. That is, if the filtration rate of a substance exceeds it Tm, the substance will begin to appear in the urine. The Tm for glucose averages 320 mg/min in an adult male.

193: According to the passage, the Tm represents the rate of plasma filtration that just exceeds the:

A) rate of concentration of the substance in the glomerular filtrate.
B) rate of concentration of the substance in the urine.
C) capacity of the kidney tubules to reabsorb the substance.
D) capacity of the bladder to store and excrete the substance.

Now, i wasn't able to figure out a good answer to this problem, and I know the credited answer is C, but that doesn't make sense either.

According to the passage, The Tm represents the capacity of the kidney tubules to reabsorb the substance.

This is markedly different from The Tm represents THE RATE OF PLASMA FILTRATION THAT JUST EXCEEDS THE the capacity of the kidney tubules to reabsorb the substance.

To me, adding in the bolded section makes no sense. Thoughts?

---

Members don't see this ad.

 

[image187]

stating the same thing different ways is something the MCAT will do to see if you'll be fooled. Don't be, think flexibly. If you keep on adding glucose to the plasma and find out that glucose spills into the urine at a plasma flow of 320 mg/min, you know this is the maximum rate the kidney can absorb it at (e.g. the Tm)