What protects the inner parts of a cell?

The inner parts of a cell or cell organelle needs to be protected from the external environment. If such a protection is not provided, toxins and other harmful molecules may access the cell interior and disrupt its working or kill it. The cell is protected from the external environment by the cell membrane.

The cell membrane is a semi-permeable structure made up of phospholipid molecules. These molecules are amphiphilic in nature. That is, they have both a hydrophobic end and a hydrophilic end. The cell membrane is a bi-lipid layer and is composed of two layers of these phospholipid molecules, with hydrophobic ends pointing inwards and hydrophilic ends pointing outwards (inside the cell and outside towards the external environment). This specialized structure allows only a few selective molecules to enter the cell, while prohibiting the entry of others and thus, it protects the inner parts of the cell.

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