Question

Lysosomes have acidic environment inside their vesicles due to

• A. Production of carboxylate ions inside it
• B. Production of phosphate ions inside it
• C. High pH compared to outside
• D. None of the above

Answer 1

Answer: (D)

To maintain their internal acidic pH, lysosomes must actively concentrate $H^{+}$ ions (protons). This is accomplished by a proton pump in the lysosomal membrane, which actively transports protons into the lysosome from the cytosol. This pumping requires expenditure of energy in the form of ATP hydrolysis, since it maintains approximately a hundred-fold higher $H^{+}$ concentration inside the lysosome.