Final answer:
The true statement about receptor-mediated endocytosis of LDL particles is C. LDL receptors in the plasma membrane associate with clathrin-coated pits.
Step-by-step explanation:
Receptor-mediated endocytosis is a process by which specific substances, like LDL particles, are brought into the cell through binding to receptors on the plasma membrane. These receptors aggregate in clathrin-coated pits, which then invaginate and pinch off to form coated vesicles. These vesicles internalize the LDL particles into the cell for further processing.
Mutations that impair the endocytosis of LDL receptors cause a drop in blood cholesterol levels. In the genetic disease familial hypercholesterolemia, defective or missing LDL receptors result in the accumulation of LDL particles in the blood, leading to high cholesterol levels and increased risk of cardiovascular disease.
The high pH inside endosomes allows LDL to dissociate from its receptor. After internalization, the coated vesicles lose their clathrin coating and fuse with early endosomes. In the acidic environment of the endosome, the low pH causes the dissociation of LDL particles from their receptors. The dissociated LDL is then processed and metabolized within the endosome. Therefore the correct answer is C. LDL receptors in the plasma membrane associate with clathrin-coated pits.