Cholesterol processing, illustration. Cholesterol molecules (yellow) are transported by low-density lipoprotein (LDL) particles (across top). The particles bind to LDL receptors (blue) on a cell's membrane (red across upper frame), resulting in their endocytosis through the cell membrane into clathrin (purple) coated endosomes. Once inside the cell the cholesterol is transported to a lysosome (centre right) where Niemann-Pick C2 (NPC2) proteins (light blue) transport the cholesterol molecules to NPC1 (dark blue) proteins embedded in the membrane. NPC1 moves the cholesterol out of the lysosome and delivers it to the endoplasmic reticulum (bottom right) for further processing. For a labelled version of this image see F032/7639.