All cells are enclosed by a thin, film like Cell membranes, plasma lemma, biological membranes or biomembranes. The plasma membrane is a semipermeable (not everything can pass through) boundary between the cell and its environment. It is made up of lipids, proteins and carbohydrates. Chemically a biomembrane consists of lipids(20-40%), proteins(50-75%) and carbohydrates (1-5%).
Functions of Plasma Membranes (Biomembranes)
5. Organelles: Cell membrane delimit a number of subcellular structures or organelles like nucleus, mitochondria, plastids, Golgi apparatus, endoplasmic reticulum, microbodies etc.