Biological Membrane & Fluid Mosaic Model
Biological membrane
Made up of phospholipid bilayer.
Makes the wall of cells and organelles.
Separates two fluid compartments, an inner compartment and an outer compartment.
Fluid Mosaic Model
Explains the fluidic nature of the biological membrane.
A biological membrane is basically a thin and strong sheet of fluid. This fluid is nothing but the two layers of phospholipid molecules.
Just like in any liquid, the phospholipid molecules are freely moving in this fluid.
Because the fluid is only two layers thin and it's very difficult for a phospholipid molecule to change the layer, the movement is only along the plane of the layer i.e. its 2-dimensional movement, rather than the 3-dimensional movement that we usually think of.
Bubble Analogy
You can compare a biological membrane with a bubble.
Just like how a bubble is a thin fluidic layer of water that separates two air compartments, a biological membrane is a thin fluidic layer of phospholipids that separates two water compartments.