Final answer:
Lysosomes maintain a low internal pH through the action of proton pumps, which actively transport hydrogen ions into the organelle, creating an acidic environment where digestive enzymes can function.
Step-by-step explanation:
Lysosomes are specialized organelles within eukaryotic cells that function as the cell's "garbage disposal," breaking down macromolecules, worn-out organelles, and pathogens. The hydrolytic enzymes within lysosomes are active at a low pH or acidic environment, typically around pH 4.5, which is much lower than the cytoplasm's pH. To maintain this low internal pH, lysosomes are equipped with proton pumps that actively transport hydrogen ions (protons) from the cytoplasm into the lysosome, thereby acidifying its contents.
This compartmentalization allows the eukaryotic cell to separate the digestive activities of lysosomes from the rest of the cell, where many biochemical reactions cannot occur at such a low pH. In the human immune response, this mechanism is important as lysosomes in white blood cells, such as macrophages, use their acid hydrolases to destroy incoming pathogens. The acidic environment ensures these enzymes are only active inside the lysosome, preventing potential damage to other cellular components.