Question

The urine of man under normal conditions do not contain glucose because
A. Glucose in the glomerular filtrate is converted into glycogen.
B. Glucose in the glomerular filtrate is reabsorbed in the uriniferous tubules.
C. Glucose of the blood is not filtered in the glomerulus.
D. The normal blood sugar is fructose.

Answer 1

Hint: The urine formation in man consists of a selective reabsorption process on which useful substances are absorbed. In proximal convoluted tubules, nearly 75 percent of filtrate is reabsorbed. Mostly all nutrients (glucose, amino acid, electrolyte, and water) are reabsorbed either through active or passive transport.

Complete answer: The process of absorption of useful substances in the glomerular filtrate is called selective reabsorption which occurs both through active transport as well as passive transport. In general, there is no presence of glucose in the urine of a man under normal condition because all the filtered glucose from the tubular fluid is reabsorbed by the kidneys and sent back into the bloodstream.
The blood is filtered by the glomerulus which produces the glomerular filtrate. Glucose, amino acid, sodium ions, etc, are reabsorbed through active transport while urea, chloride, and water are reabsorbed through passive transport. Glucose is reabsorbed 100 percent through a carrier molecule immediately into the blood capillaries. Water reabsorption in PCT is called obligatory reabsorption because most water is reabsorbed here. The filtrate is collected and entered the tubules through the bowman’s capsule. Water and salts needed by the body are reabsorbed into the blood capillaries and the rest of the filtrate travels through the tubules water and salts needed by the body are reabsorbed into the blood capillaries.
So, the correct answer for the above question is option (B).

Note: The glomerular filtrate besides containing harmful products, also contains useful substances like glucose, water, amino acid, sodium ions, etc. About 99 percent filtrate is reabsorbed and reabsorption is maximum in PCT, where almost all glucose is reabsorbed into blood capillaries.