Question

Why is the plasma membrane called a selectively permeable membrane?

NCERT Class IX
Sciences - Main Course Book

Chapter 5. The Fundamental Unit of Life

Answer 1

Plasma membrane is also called a semi permeable membrane or a selectively permeable membrane as it prevents the entry and exit of some materials in and out of the cell and also controls the movement of some other materials inside the cell. 

Answer 2

The cell membraneor the plasma membranies known as a selectively permeable membrane because it regulates the movement of substance in and out of the cell. this means that the plasma membrane allows the entry of only some substance and prevents the movement of some other material