Question

Proximal convoluted tubule of nephron is responsible for the
A. Filtration of blood.
B. Maintenance of glomerular filtration rate.
C. Selective reabsorption of glucose, amino acid, NaCl and water.
D. Reabsorption of salts only.

Answer 1

Hint: The convoluted portion of vertebrate nephron reabsorb the sugar, water, sodium and chloride ions from the glomerular filtrate.

Complete Answer:
The nephron is the structural and functional microscopic unit of the kidney. It comprises a renal corpuscle and a renal tubule. The renal corpuscle comprises a bunch of capillaries called a glomerulus and a Bowman's capsule. The renal tubule is extended from the capsule. The capsule and the tubule are associated and made up of epithelial lumen cells. A normal adult has between 1-1.5 million nephrons in each renal.
The glomerulus is a bunch of narrow blood vessels called capillaries found inside the Bowman capsule in the kidney. Glomerulus includes podocytes that assist with the filtration of blood and the development of glomerular filtrate.
The glomerular filtration rate is maintained by the rate of blood flow through the afferent arterioles, but does not depend on the proximal convoluted tubule.
The proximal convoluted tubule is the extension of the Bowman capsule. It assists with the reabsorption of much NaCl, water, glucose and amino acids due to the involvement of certain transporters and aquaporins.
Proximal convoluted tubule aid in the reabsorption of not only salts, but also sugar, glucose and amino acids.

Thus, the correct answer is option C. i.e., Selective reabsorption of glucose, amino acid, NaCl and water.

Note: The four processes used to produce and maintain the filtrate (which transforms blood to urine) are filtration, reabsorption, secretion and excretion. Filtration happens in the glomerulus and is essentially passive: it relies on intracapillary blood pressure.