cell communication

Phospholipid Bilayer

A structure composed of hydrophilic heads and hydrophobic tails that forms the basis of the plasma membrane.

Fluid Mosaic Model

A model describing the plasma membrane as a dynamic structure with various proteins embedded within the phospholipid bilayer.

Integral Proteins

Proteins that span the bilayer of the plasma membrane and are essential for function but cannot be removed without damaging the membrane.

Peripheral Proteins

Proteins loosely attached to the surface of the membrane that can be removed without damaging the membrane.

Passive Transport

Movement of molecules across the membrane without the use of energy, down their concentration gradient.

Active Transport

Movement of molecules against their concentration gradient, requiring energy, typically in the form of ATP.

Osmosis

The movement of water across a selectively permeable membrane through aquaporins.

Cholesterol

A type of sterol found in animal cell membranes, which helps maintain fluidity at different temperatures.

Selective Permeability

The property of the plasma membrane that allows certain molecules to pass through while restricting others.

Lateral Movement

The rapid movement of lipids and proteins within the same layer of the membrane, estimated to occur around 10 million times per second.

Flip-flop Movement

The rare movement of lipids from one layer of the bilayer to the other, approximately once a month.

Saturases

Enzymes that add hydrogens to fatty acids, increasing their saturation.

Desaturases

Enzymes that remove hydrogens from fatty acids, creating double bonds and reducing saturation.

Simple Diffusion

The process by which small, nonpolar molecules move directly through the lipid bilayer without assistance.

Facilitated Diffusion

Transport of molecules across the membrane via specific channel or carrier proteins that do not require energy.