Question

The kidneys aid in acid-base balance by altering the rate of reabsorption of which of the following?

1) Sodium ions
2) Potassium ions
3) Calcium ions
4) Hydrogen ions

Answer 1

The kidneys maintain acid-base balance by altering the reabsorption rate of hydrogen ions (H+). This process involves exchanging sodium ions for H+ in renal tubules, creating bicarbonate ions, and regulating the pH of the blood.

Step-by-step explanation:

Acid-Base Balance and Kidney Function

The kidneys aid in acid-base balance by altering the rate of reabsorption of hydrogen ions (H+). This crucial function is part of the body's regulatory system that maintains the pH of blood within a narrow, healthy range. The kidneys do this by secreting or reabsorbing H+ and bicarbonate ions (HCO3-), depending on the body's current pH level.

Steps in Reabsorption and Secretion

1. 
   
3. Sodium ions are reabsorbed from the filtrate in exchange for H+ by an antiport mechanism in the apical membranes of the renal tubule cells.
4. 
   
6. The cells produce bicarbonate ions that can be released into peritubular capillaries.
7. 
   
9. When carbon dioxide (CO2) is present, a reaction forms carbonic acid, which dissociates into bicarbonate and a new hydrogen ion. However, this reaction also depends on the presence of enzymes like carbonic anhydrase.

Moreover, the kidneys are involved in maintaining homeostasis of mineral ions in extracellular fluid. These actions are part of a wider set of mechanisms controlling mineral ion concentration and water composition of the blood to maintain overall health and function.