The plasma membrane is a bilayer of lipids and proteins that forms a barrier between the inside and outside of a cell. It contains two different types of lipids: phospholipids and glycolipids. These lipids are both hydrophilic and hydrophobic, and contain phosphate and glycerol. Each type has its own characteristics and functions.
Phospholipid Bilayer Membrane
The plasma membrane is composed of phospholipids, cholesterol, and proteins. These molecules slide past each other in a mosaic-like fashion, creating a complex, dynamic structure. Phospholipids and proteins move around these needles, allowing the lipids to flow around them and back together in a seamless manner.
The all cells are surrounded by a membrane. which is a characteristic of a cell membrane functions to transport materials into and out of cells. Depending on the type of transport, these substances can be moved passively or actively. Passive transport does not use cellular energy, but active transport is energy-intensive and requires a source of ATP.
A lipid bilayer structure provides a first level of control. This allows only certain types of substances to cross the membrane. This structure also enables selective permeability. Nonpolar materials are able to cross it easily, while water-soluble materials need assistance to cross. This is because the hydrophobic tails of the phospholipid bilayer block the entry of water-soluble substances.
