Which of the following substances is most likely to be brought into cell by receptor-mediated endocytosis?
To determine which of the following substances is most likely to be brought into a cell by receptor-mediated endocytosis, we need to understand what receptor-mediated endocytosis is and how it works.
Receptor-mediated endocytosis is a selective process by which cells internalize specific molecules from the extracellular environment. It involves the interaction of specialized receptors on the cell membrane with specific ligands, leading to the formation of vesicles that transport the ligands into the cell.
Now, let's consider the substances:
1. Glucose: Glucose is a simple sugar that can be transported into cells by facilitated diffusion or active transport, but not specifically through receptor-mediated endocytosis.
2. Cholesterol: Cholesterol is an important lipid molecule involved in various cellular processes. It is primarily taken up by cells through a process called receptor-mediated endocytosis. Receptors on the cell membrane, such as the LDL receptor, bind to cholesterol-containing particles like LDL (low-density lipoprotein), leading to their internalization.
3. Sodium ions: Sodium ions (Na+) are small, charged particles that are primarily transported across cell membranes through specific ion channels or by active transport pumps. Receptor-mediated endocytosis is not involved in the uptake of ions like sodium.
4. Antibodies: Antibodies are large proteins produced by the immune system to target and neutralize foreign substances (antigens). They can participate in receptor-mediated endocytosis when they bind to specific receptors expressed on cells, leading to internalization of the antigens they are bound to.
Based on this information, the substance most likely to be brought into the cell by receptor-mediated endocytosis would be antibodies (option 4).