What are the differences between separating gel and stacking gel?

Basis of differentiation 

Stacking gel

Separating gel

Definition 

Is a low concentrated polyacrylamide gel used in SDS-PAGE technique to concentrate molecules into a tight band, readying them for separation in the separating gel

Is a highly concentrated polyacrylamide gel used in SDS-PAGE technique to separate molecules based on size, revealing the composition of the sample

% of polyacrylamide in the gel

Has a lower percentage of polyacrylamide - about 4%, leading to larger pore sizes

Has a higher percentage of polyacrylamide – around 10% resulting in smaller pore sizes and finer matrix 

Pore Size

Has larger pore size that enables rapid movement of proteins and helps proteins concentrate at the interface with the separating gel

Has smaller pore size that restricts the movement of proteins, promoting separation based on molecular weight

pH 

Has a lower pH of 6.8

Has a higher pH of 8.8

Placement

Is placed on top of the separating gel

Is placed at the bottom of the gel electrophoresis container

Resolution 

Gives lower resolution 

Gives better

Function 

To line up and stack proteins into a tight band, so they can enter the resolving gel at the same time

To separate proteins based on molecular weight