Final answer:
SDS-PAGE is used to separate proteins based on size, while in Western blot, proteins from SDS-PAGE are probed with an antibody to detect a specific protein.
Step-by-step explanation:
The main difference between SDS-PAGE and Western blot is the purpose and technique used for protein separation and detection. SDS-PAGE is a technique used to separate proteins based on their size, while Western blot is a method used to detect a specific protein in a sample. In SDS-PAGE, proteins are denatured and run on a gel to separate them based on size. In Western blot, separated proteins from SDS-PAGE are transferred to a membrane and then probed with an antibody specific to the target protein to visualize its presence.