both in cells and extracellular fluids , dibasic phosphate `(HPO_(4) ^(2-)) ` and monobasic phosphate `(H_(2) PO_(4)^(-))` act as acid base buffers to maintain

Options

A. (a) `K^(+)` concentration of extracellar fluid
B. (b) `Na^(+) ` concentration of extraceller fluid
C. (c) `Na^(+)` concentration of cellular fluid
D. (d) `H^(+)` concentration of celluar fluid

Answer

### Step-by-Step Solution:

1. **Understanding the Role of Buffers**: Buffers are substances that help maintain a stable pH in a solution, resisting changes in acidity or alkalinity when small amounts of acids or bases are added. In biological systems, maintaining the pH is crucial for proper cellular function.

2. **Identifying the Buffers**: In this case, the dibasic phosphate `(HPO₄²⁻)` and monobasic phosphate `(H₂PO₄⁻)` act as acid-base buffers. They can neutralize excess acids or bases, thereby stabilizing the pH levels in cells and extracellular fluids.

3. **Defining pH**: The pH scale measures the concentration of hydrogen ions `(H⁺)` in a solution. A lower pH indicates higher acidity (more H⁺ ions), while a higher pH indicates alkalinity (fewer H⁺ ions). The neutral pH is around 7.

4. **pH Levels in Cells**: The typical pH level of living cells is approximately 7.2, which is slightly above neutral. This indicates a balance between acidity and alkalinity, essential for various biochemical processes.

5. **Analyzing the Options**: The question provides several options related to what the dibasic and monobasic phosphates help maintain:
- A) Potassium concentration of extracellular fluid
- B) Sodium concentration of extracellular fluid
- C) Sodium concentration of cellular fluid
- D) H⁺ concentration of cellular fluid

6. **Selecting the Correct Answer**: Since the pH level is directly related to the concentration of hydrogen ions `(H⁺)`, the correct answer is D) H⁺ concentration of cellular fluid. This is because the pH is a measure of the concentration of H⁺ ions, and maintaining this concentration is crucial for the stability of pH in cells and extracellular fluids.

### Final Answer:
The dibasic phosphate `(HPO₄²⁻)` and monobasic phosphate `(H₂PO₄⁻)` act as acid-base buffers to maintain the **H⁺ concentration of cellular fluid**.

---