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MCAT Question A Day - 7/24/13 - Answer!

Which of the following organelles are not associated with the breakdown of potentially harmful substances?

A.  Lysosomes
B.  Peroxisomes
C.  Smooth ER
D.  Rough ER

The correct answer is (D). Rough ER is primarily responsible for synthesizing membrane proteins and secretory proteins. Peroxisomes break down hydrogen peroxide and other toxins, smooth ER plays a role in drug detoxification, and lysosomes break down various molecules that originate inside and outside the cell.