Identify the statements which are true with respect to the function of a nephron.
1. Approximately 1500 ml - 1600 ml of blood is filtered by the kidneys per minute.
2. Proximal Convoluted Tubule absorbs nearly 70-80 percent of electrolytes and water.
3. Nearly all the filtered essential nutrients are absorbed by the Distal Convoluted Tubule.
4. Collecting ducts allow passage of small amounts of urea into the medullary interstitium to keep up osmolarity.

Correct option is D

The nephron is the functional unit of the kidney, responsible for filtration, reabsorption, and excretion.
· (1) Approximately 1500 ml - 1600 ml of blood is filtered by the kidneys per minute – Incorrect, as this is the renal blood flow, but not all of it is filtered by the nephron.
· (2) Proximal Convoluted Tubule absorbs nearly 70-80 percent of electrolytes and water – Correct, as most essential reabsorption occurs here.
· (3) Nearly all the filtered essential nutrients are absorbed by the Distal Convoluted Tubule – Incorrect, as majority of nutrients are reabsorbed in the proximal tubule, not distal.
· (4) Collecting ducts allow passage of small amounts of urea into the medullary interstitium to keep up osmolarity – Correct, as this process helps in maintaining concentration gradients for urine formation.
Explanation of Other Options:
· (a) 1 and 3 – Incorrect, as statement 3 is wrong.
· (b) 2, 3, and 4 – Incorrect, as statement 3 is wrong.
· (c) 1, 2, and 3 – Incorrect, as statement 3 is wrong.
· (d) 2 and 4 – Correct answer, as these are valid nephron functions.