Structure and function of plasma membrane
The plasma membrane, or cell membrane, is a flexible, thin barrier that surrounds the
cytoplasm of a cell and separates it from its surroundings. It is made up of a lipid bilayer,
consisting of two layers of phospholipid molecules, with hydrophilic heads and hydrophobic
tails.
The primary function of the plasma membrane is to control the movement of substances in and
out of the cell. Due to the hydrophobic nature of the lipid bilayer, most molecules, including
ions and polar molecules, cannot pass through the membrane without the assistance of specific
transport proteins.
However, the plasma membrane contains various proteins that permit particular molecules to
pass through. Some proteins function as channels, forming pores that allow selective molecules
or ions to pass through, while others act as carriers, binding to specific molecules and
transporting them across the membrane.
Furthermore, the plasma membrane is involved in cell signaling and communication. It contains
receptor proteins that bind to signaling molecules like hormones and neurotransmitters,
triggering a response inside the cell.
The plasma membrane is also responsible for cell adhesion, which is the process by which cells
attach to one another and to the extracellular matrix. Integrins, a type of protein present in the
plasma membrane, link to extracellular matrix proteins, anchoring the cell in place.
In summary, the plasma membrane is a critical component of the cell, controlling its interaction
with the environment, and playing a significant role in preserving homeostasis, which is vital for
the cell's survival and function.
• Transport across membranes: active, passive, diffusion and
osmosis.
The movement of molecules and ions across the cell membrane is known as transport across
membranes. This process can occur through a variety of mechanisms, including passive and
active transport, as well as diffusion and osmosis.
