Biological Membranes Structure and Function
Cell membranes are like intelligent bouncers at a club - they decide what gets in and what stays out. The plasma membrane forms a barrier between your cell and the environment, whilst intracellular membranes divide cells into different compartments, making everything run more efficiently.
The fluid mosaic model explains how membranes work. Picture a sea of phospholipids with their water-loving heads facing out and water-hating tails tucked inside. This creates a barrier that water-based substances can't cross easily, but fat-soluble ones slip through no problem.
Cholesterol slots between phospholipids like a stabiliser, making the membrane stronger and less leaky. Channel proteins and carrier proteins act as special doorways - channels let small charged particles like water through, whilst carriers transport larger molecules across the membrane.
Key Point: Think of the membrane as a busy motorway with specific lanes (proteins) for different types of traffic (molecules).
Cell signalling happens when one cell releases messenger molecules like hormones, which travel to target cells and bind to specific receptors. It's like sending a text message that only certain phones can read because they have the right app installed.
