Chapter 11, Problem 1A

Summary Introduction

Introduction:

The kidney gland filters the ions, metabolites and excretes the metabolic nitrogenous wastes from the body. The acid base balance is balanced by the exchange of the ions in the interstitial fluid and tubules of the nephrons in the kidney. The movement of hydrogen ions and bicarbonate ions balances the pH in the blood and nephrons of the kidney.

Answer to Problem 1A

Correct answer:

The acid-base balance in the kidney is maintained by the exchange of hydrogen and bicarbonate ions in the nephrons of the kidney. The movement of ions takes place across the ion channel receptors called as aquaporins in the membrane. Therefore, option (c) is correct.

Explanation of Solution

Reason for the correct statement:

The excretion of the metabolite urea is not related to the maintenance of acid-base balance in the kidney. The excretion of nitrogenous wastes like urea takes place as a result of the byproduct formed in the urea cycle. The acidbase balance is maintained by the movement of hydrogen and bicarbonate ions in the tubules and interstitial fluid.

Option (c) is given as “maintains the acid-base balancerids the body of uric acid”.

As “the acid-base balance is regulated by the movement of the bicarbonate and hydrogen ions across the membrane of the nephrons and peritubular capillaries”, it is the right answer.

Hence, option (c) is correct.

Reasons for the incorrect statements:

Option (a) is given as “excretes metabolic wastesrids the body of urea”.
The metabolic wastes are excreted from the kidney through the urine like urea. As the mentioned statement is correct, so it is a wrong answer.

Option (b) is given as “maintains the watersalt balance-helps regulate blood pressure”.
The water salt balance is maintained by the secretion of hormone aldosterone from adrenal gland and anti-diuretic hormone from posterior pituitary gland. The secretion of aldosterone maintains the concentration gradient of ions in the tubules. The secretion of anti-diuretic hormone causes the reabsorption of the water in the distal convoluted tubules and collecting duct. As the mentioned statement is correct, so it is a wrong answer.

Option (d) is given as “secretes hormonessecretes erythropoietin”.
The synthesis of t red blood cells is caused by the secretion of the erythropoietin hormone. As the mentioned statement is correct, so it is a wrong answer.

Hence, options (a), (b) and (d) are incorrect.

Conclusion

The acid-base balance is maintained in the kidney by the movement of hydrogen and bicarbonate ions in the nephrons of the kidney. This balance is not related to the excretion of the urea from the body. The excretion of nitrogenous wastes takes place in the urine as a result of the byproduct of the urea cycle.