Which of the following enables a cell to concentrate and take in a specific kind of molecule?

• A. Receptor-mediated endocytosis
• B. Facilitated diffusion
• C. Simple diffusion
• D. Osmosis

Answer: (A)

Verified step by step guidance

1. Understand the key terms in the question: 'concentrate' and 'specific kind of molecule.' This suggests a process that is selective and involves active participation by the cell.
2. Review the concept of receptor-mediated endocytosis. This is a process where specific molecules bind to receptors on the cell membrane, triggering the cell to engulf the molecule into a vesicle. This allows the cell to concentrate specific molecules.
3. Compare receptor-mediated endocytosis with the other options: Facilitated diffusion, Simple diffusion, and Osmosis. Facilitated diffusion and simple diffusion are passive processes that do not involve specificity or concentration of molecules. Osmosis is the movement of water, not specific molecules.
4. Eliminate the incorrect options based on their definitions: Facilitated diffusion and simple diffusion are not selective for specific molecules, and osmosis is unrelated to the uptake of specific molecules.
5. Conclude that receptor-mediated endocytosis is the correct answer because it is the only process that enables a cell to selectively concentrate and take in specific molecules using receptors.