Membrane structure

What forms the structural basis of all membranes

Phospholipid bilayer

Which part of the phospholipid bilayer provides a barrier to the movement of most polar molecules and ions

Non-polar fatty acid tails

What is the fluid mosaic model

A representation of membrane structure which is consistent with available data.

Why are membranes described as fluid

Molecules can move around within a monolayer unless anchored to the cytoskeleton.

Why are membranes described as mosaic

Refers to the appearance of the different molecules (phospholipids and proteins) when viewed from above.

What are the 2 type of membrane proteins

intrinsic (or integral) and extrinsic (or peripheral)

Intrinsic proteins

They are embedded in the phospholipid bilayer and span the bilayer.

Extrinsic proteins

They are not embedded in the phospholipid bilayer but are associated with one side of the membrane.

Cholesterol

Small molecule that fits in between the fatty acid tails and stabilises the membrane by binding to the fatty acid tails.

Controls the fluidity of the membrane and helps prevent polar molecules and ions crossing the membrane.

Proteins

Act as channels or carriers to transport polar molecules and ions across the membrane via facilitated diffusion or active transport.

Also act as enzymes e.g. ATP synthase in mitochondria.

Glycoproteins

Proteins modified in the Golgi apparatus by the addition of carbohydrate chains.

Act as antigens for cell recognition as self or non-self and act as receptors for chemical signals e.g. hormones to allow cell-to-cell signaling.

Also help cell adhesion to form tissues.

Glycolipids

Lipids modified in the Golgi apparatus by the addition of carbohydrate chains.

Act as antigens for cell recognition and help cell adhesion to form tissues.