structure and functions of membranes

What are cell membranes used for

Signalling, transporting and sensing

What is the fluid mosaic model

1972

Fluid = phospholipid bilayer which is constantly moving

Mosaic = proteins embedded in bilayer

What is the structure of the bilayer

Hydrophilic phosphate head and a hydrophobic lipid tail

What is the structure of the membrane

Phospholipid bilayer

Cholesterol to add stability

Proteins

Glycoproteins

Glycoliopids

Why is the bilayer structured in the way it is

So that the centre is hydrophobic, which makes sure water solvable substances cannot pass but lipid solvable substances can

What is the need for cholesterol

Provide stability

Has regions of hydrophilic and hydrophobic

Hydrophobic regions bind to phospholipid tails so that they are closer together and reduces fluidity

What are the 2 types of protein in a membrane

Intrinsic and extrinsic

Intrinsic proteins

Embedded through both sides of bilayer

Include channel and carrier proteins to transport large molecules and ions

Extrinsic proteins

On one side of bilayer

Provide support to membrane and involved in cell signalling

Glycoproteins

Intrinsic proteins attached to carbohydrates

Glycolipids

Lipids attached to carbohydrates

What are glycoproteins and glycolipids involved in

Cell adhesion - attachment of cells to each other

Cell recognition - cells recognise each other

Cell signalling - communication between cells

What are the 2 main types of cell membranes

Cell surface membranes and membranes around organelles

What is the purpose of cells surface membranes

Surround cells and act as a barrier between cell and environment, control what enters/exits

What is the purpose of membranes around organelles

Compartmentalisation