AEMCA Practice Exam

What does intracellular buffering primarily use to stabilize pH?

1. Water and sodium

2. Proteins and phosphates

3. Calcium and magnesium

4. Carbohydrates and lipids

The correct answer is: Proteins and phosphates

Intracellular buffering primarily utilizes proteins and phosphates to stabilize pH levels within cells. This is crucial for maintaining the internal environment of the cell, as small changes in pH can significantly impact cellular functions and biochemical reactions. Proteins serve as excellent buffers because they contain amino acids with side chains that can either donate or accept protons (H+ ions), depending on the pH of the environment. This ability allows proteins to resist changes in pH by binding or releasing protons as needed, thus maintaining a relatively stable internal environment. Phosphates, particularly in the form of dihydrogen phosphate (H2PO4-) and hydrogen phosphate (HPO4^2-), also play a significant role in buffering. They work through a similar mechanism, providing a source of protons or binding them to help stabilize the pH within the cell. The phosphate buffer system is especially important in situations where there are shifts in intracellular pH, such as during metabolic processes. Alternative choices do not serve this buffering role effectively. While water, sodium, calcium, magnesium, carbohydrates, and lipids are important for various cellular functions, they do not have the inherent chemical properties needed to buffer pH levels inside cells like proteins and phosphates do,