Topic overview

Start with the big picture

The membrane’s amphipathic phospholipids form a bilayer, with hydrophilic heads facing aqueous environments and hydrophobic tails oriented inward. In the fluid-mosaic model, lipids and proteins can move laterally, while membrane asymmetry and cholesterol contribute to membrane properties. Integral and peripheral proteins have different relationships to the bilayer, and the extracellular glycocalyx supports recognition, adhesion, and protection. Selective permeability distinguishes molecules that cross readily from ions and larger polar solutes that generally require transport proteins. The lesson’s transport overview includes diffusion, active transport, and vesicular transport, alongside channels, carriers, and pumps that help maintain electrochemical gradients. It also considers lipid rafts and factors that influence membrane fluidity.