Introduction:

The plasma membrane is the outermost covering of the cell that separates the cell's internal environment from the external environment. It is also called a selectively permeable membrane because it regulates the movement of substances in and out of the cell.

What is a selectively permeable membrane?

A selectively permeable membrane is a membrane that allows some molecules and ions to pass through it while blocking others. The plasma membrane is selectively permeable because it allows some molecules and ions to pass through it while blocking others.

How does the plasma membrane regulate the movement of substances?

The plasma membrane has two main mechanisms for regulating the movement of substances in and out of the cell: passive transport and active transport.

Passive transport:

Passive transport is the movement of substances from an area of high concentration to an area of low concentration and does not require energy. The three main types of passive transport are diffusion, osmosis, and facilitated diffusion.

Active transport:

Active transport is the movement of substances from an area of low concentration to an area of high concentration and requires energy. The two main types of active transport are primary active transport and secondary active transport.

Conclusion:

In conclusion, the plasma membrane is called a selectively permeable membrane because it regulates the movement of substances in and out of the cell. It allows some molecules and ions to pass through it while blocking others. The plasma membrane has two main mechanisms for regulating the movement of substances: passive transport and active transport. Passive transport does not require energy, while active transport requires energy.

The Plasma Membrane is a selectively permeable membrane as it only allows entry and exit of some selected molecules into and out of the Cells. It also prevents movement of some other materials, therefore the plasma membrane is called a selectively permeable membrane.