Final answer:
The lysosome is more acidic than the cytosol because it contains proton pumps that lower its pH to around 4.5 to activate hydrolytic enzymes, compared to the neutral pH of 7.0 in the cytosol.
Step-by-step explanation:
The interior of a lysosome is more acidic than the cytosol due to the presence of hydrolytic enzymes that require a low pH to function effectively. These enzymes, known as acid hydrolases, are responsible for breaking down various biomolecules such as proteins, polysaccharides, lipids, and nucleic acids. Furthermore, lysosomes contain proton pumps in their membranes that actively transport hydrogen ions (protons) into the lumen to maintain the acidic environment, which has an optimal pH around 4.5. In contrast, the pH of the cytosol is typically neutral, around 7.0 in humans, which is not conducive for these enzymes to act. This compartmentalization allows the breakdown of macromolecules and pathogens within lysosomes without affecting the rest of the cell.