During receptor-mediated endocytosis, Select one:
a. a small channel forms beneath the receptors
b. a vesicle is destroyed
c. plasma membrane receptors bind molecules to be expelled
d. a vesicle forms
e. a pit opens inside a cell
The correct answer and explanation is:
The correct answer is d. a vesicle forms.
Receptor-mediated endocytosis is a process by which cells internalize molecules from their environment, specifically those that bind to cell surface receptors. This form of endocytosis is highly selective, meaning that only specific molecules are brought into the cell.
The process begins when certain molecules, known as ligands, bind to receptors located on the plasma membrane. These receptors are typically proteins or glycoproteins that are specialized to recognize and bind particular molecules. Once the ligand binds to the receptor, this triggers a conformational change in the receptor, leading to the formation of a pit on the cell membrane.
This pit, which is coated with a protein called clathrin, begins to invaginate (fold inward) to form a small, vesicle-like structure. The vesicle pinches off from the plasma membrane, and the clathrin coating is typically shed once the vesicle is inside the cell. The vesicle, now enclosed with the ligand molecules inside, can then fuse with early endosomes, where the ligands can be processed further.
The vesicle that forms during receptor-mediated endocytosis is important because it allows for the selective intake of specific substances, such as nutrients, hormones, or other signaling molecules. This mechanism also helps regulate the number of receptors on the cell surface, since the internalization of receptors and ligands can control how many remain available for future interactions.
In summary, receptor-mediated endocytosis involves the formation of a vesicle as the primary mechanism for internalizing molecules into the cell. This process is crucial for cellular function, as it allows cells to selectively absorb and regulate the uptake of specific substances.