Final answer:
Endosomes have a low pH because proton pumps move hydrogen ions into them to create an acidic environment, which is crucial for the function of degradative enzymes and certain drug delivery systems.
Step-by-step explanation:
The low pH inside endosomes is due to the action of proton pumps that actively transport hydrogen ions (H+) into the organelle, creating an acidic environment. This acidic pH is necessary for the optimal activity of various enzymes responsible for breaking down biomolecules, a process essential for cellular digestion and recycling.
It also aids in the function of Nano systems designed for targeted drug delivery, as some materials can be engineered to release their cargo in response to the acidic conditions, taking advantage of the lower pH in endosomes compared to the rest of the cell and certain pathological conditions such as tumors.