Ans.
Internal membranes are defined as membranes that enclose eukaryotic cell organelles, such as mitochondria, nucleus, and endoplasmic reticulum. Like plasma membranes, internal membranes are made up phospholipids and membrane proteins.
The internal membranes play an important role in eukaryotic cells, as these membranes encase or enclose the cell organelles and regulate the exchange of essential components inside the cell.