Practice Passage Test - 2 | Practice Passages for MCAT PDF Download

Passage

The study of cell membranes in biochemistry is still an ongoing field, with many aspects yet to be fully understood. Cell membranes serve functions beyond enclosing and compartmentalizing cells and organelles. They also regulate the transport of substances in and out of the cell, provide sites for enzyme binding and catalysis, direct the function of cell organelles, and anchor filaments. Due to the complexity of cell membranes, their dysfunction is often involved in various diseases. One significant category of cell membrane diseases is related to disruptions in membrane trafficking. Approximately 10% of cellular proteins are involved in this process. Niemann-Pick disease type C (NPC) is a rare and interesting lysosomal storage disorder that is currently under study. NPC is characterized by the absence of an enzyme necessary for normal cell recycling, resulting in the accumulation of harmful materials within the cell and subsequent deterioration. Specifically, NPC leads to the lysosomal buildup of LDL-derived cholesterol. Recent research has identified a malfunction in the NPC1L1 protein as a cause of NPC. This protein is involved in the intracellular trafficking of cholesterol in the small intestine. The drug ezetimibe is used to treat NPC and was initially introduced without certainty regarding its target protein. Only recently has it been determined that the specific target of ezetimibe is NPC1L1. As our understanding of the complexities of cell membranes grows, so does our knowledge of how to effectively treat related diseases.