Question

Human urine is usually acidic because.

• A. Sodium transporter exchanges one hydrogen ion for each sodium ion, in peritubular capillaries
• B. Excreted plasma proteins are acidic
• C. Potassium and sodium exchange generates acidity
• D. Hydrogen ions are actively secreted into the filtrate

Answer 1

The correct option is D

Hydrogen ions are actively secreted into the filtrate

The correct option is D.

Explanation of the correct option:

Option D:

1. The acidity of urine is due to the deposition of H⁺ ions in the filtrate.
2. Hydrogen ions decrease the pH of the urine, hence making it acidic.
3. The pH of the filtrate reduces to 6.

Explanation of the incorrect option:

Option A:

1. Peritubular capillaries help in the reabsorption of nutrients from the blood in the kidney.
2. They form the blood vessels that surround the proximal and distal convoluted tubule and Henle's loop.
3. They do not contribute to the acidity of filtrate.

Option B:

1. The plasma proteins that are excreted are acidic.
2. But these proteins do not contribute to the acidity of filtrate.
3. These plasma proteins are also known as blood proteins.

Option C:

1. Potassium and sodium exchange may lead to a change in ion concentration.
2. Potassium and sodium exchange do not contribute to the acidity of plasma proteins.

Final answer: Human urine is usually acidic because hydrogen ions are actively secreted into the filtrate.