What is the semi-permeable nature of the cell membrane referred to as?

The semi-permeable nature of the cell membrane is referred to as selective permeability. This term describes the characteristic of the cell membrane that allows certain substances to pass through while blocking others. The structure of the cell membrane, which is primarily composed of a lipid bilayer, contains proteins that help control which materials enter and exit the cell.

Selective permeability is crucial for maintaining homeostasis within the cell, as it regulates the internal environment by allowing essential nutrients in, removing waste products, and preventing harmful substances from entering. This selective process is vital for cellular function, as different types of molecules—including ions, water, and larger organic compounds—are managed differently based on the needs of the cell.

In contrast, active transport refers to the movement of molecules against their concentration gradient and requires energy, while passive diffusion describes the movement of molecules down their concentration gradient without energy input. Osmosis specifically pertains to the diffusion of water across a semi-permeable membrane, a subset of the broader concept of selective permeability.