Selective permeable means- to allow some molecules to pass and inhibit other molecules.
Explanation: The capacity to filter molecules to transport in or out of the cell is selective permeability.
Selective permeable membrane facilitates passage of specific molecules on the basis of some specific criteria. This kind of transport is ACTIVE TRANSPORT and requires energy.
Example is lipid bilayer of the cell membrane. It has both semipermeable abd selective permeable quality. The semipermeable layer allows passage of uncharged solutes. Lipid soluble molecules as fat soluble vitamins and some hormones can pass through the hydrophilic layer. Water can pass through the semipermeable membrane by osmosis and carbon dioxide and oxygen can pass through diffusion from this semipermeable membrane.
But for polar molecule, small ions, it is not easy to pass through this lipid bilayer. They passed through the transmembrane channels. Other large molecules pass through active transport. In active transport energy is required in the form of ATP.
Cytotoxic T cells secrete granzymes and perforins when targeting cells. Additionally they secrete cytokines such as IFN-, TNF-α and TNF-β that act to activate macrophages and help kill infected cells.
