What does the presence of a cell membrane imply about the cell's internal environment?

📌 CONCEPT: The presence of a cell membrane implies that the cell's internal environment is highly regulated and isolated from the external environment, allowing for maintenance of homeostasis and balance of solutes and water inside the cell.

📐 RULE / FORMULA: The cell membrane's selective permeability ensures that only specific substances can pass through, which helps in maintaining the internal environment. This is achieved through the process of diffusion and osmosis.

💡 WORKED EXAMPLE: For instance, a cell in a hypertonic environment will have water molecules flowing out of the cell due to osmosis, while a cell in a hypotonic environment will have water molecules flowing into the cell. The cell membrane regulates this movement to maintain homeostasis.

⚠️ COMMON MISTAKE: Students often assume that the cell membrane is completely impermeable, whereas in reality, it is selectively permeable, allowing certain substances to pass through while restricting others.