**BMAT Prep Question Analysis - Q257 & Q25**

**Q257 Consider two graphs:**

**Graph A: y = 4x**

**Graph B: y = 9/x + 16**

**At what values of x do they meet?**

a. x = -0.5 and x = +0.5

b. x = +4.5 and x = -4.5

c. x = +0.5 and x = -4.5

d. x = -0.5 and x = +4.5

e. They don't meet.

**Q25 A patient comes to the local GP. A urine dipstick test shows that there is glucose in the patient's urine sample. This means that:**

a. Glucose transporters in the loop of Henle are not functioning properly

b. The patient is healthy, since glucose normally appears in the urine

c. The proximal tubule is over-secreting glucose

d. Glucose influx into the filtrate is occurring faster than it can be reabsorbed

e. None of the above

**Answer and Explanation**

**Q257 Answer:** d. x = - 0.5 and x = + 4.5

**Explanation:** When the graphs meet, we have

4x = 9/x + 16

This gives: 4x^{2} = 16x + 9 i.e. 4x^{2} - 16x - 9 = 0.

This can be written as: (2x - 4)^{2} - 25 = 0

i.e. 2x - 4 = 5 (which gives x = + 4.5)

or 2x - 4 = - 5 (which gives x = - 0.5)

**Q25 Answer**: d. Glucose influx into the filtrate is occurring faster than it can be reabsorbed

**Explanation**: Glucose is normally completely reabsorbed from the glomerular filtrate into the proximal convoluted tubule via co-transporters (along with amino acids and inorganic phosphate) and thus does not appear in the urine. When glucose does appear in the urine, it means that the glucose transporters in the proximal convoluted tubule are saturated and are unable to reabsorb all the glucose from the filtrate. This can occur in diabetes when the patient has a higher blood glucose level than normal, thus saturating the transporters.

Drafted by Quincy (BMAT Prep)