USA Biology Olympiad (USABO) Practice Exam

In Pompe's disease, which organelle is primarily malfunctioning?

1. Nucleus

2. Mitochondria

3. Lysosome

4. Endoplasmic reticulum

The correct answer is: Lysosome

In Pompe's disease, the primary malfunctioning organelle is the lysosome. This condition is a genetic disorder caused by a deficiency in the enzyme acid alpha-glucosidase, which is necessary for the breakdown of glycogen within the lysosomes. When this enzyme is absent or malfunctioning, glycogen accumulates within lysosomes, leading to cellular and tissue damage, particularly in muscles and the heart. Understanding the role of the lysosome helps clarify why it is central to Pompe's disease. Lysosomes are responsible for degrading biomolecules, and their malfunction can result in the buildup of materials that disrupt cellular function. In the case of Pompe's disease, the accumulation of glycogen leads to various health issues, including muscle weakness and cardiomyopathy. The other organelles have different functions; for instance, the nucleus is involved in genetic material storage and regulation of gene expression, mitochondria are responsible for energy production, and the endoplasmic reticulum is involved in protein synthesis and lipid metabolism. None of these directly relate to the specific enzymatic deficiency and resulting glycogen accumulation characteristic of Pompe's disease.