Cell Biology, Fall 2008
Lab Exercise: Protein Extraction and Purification
Proteins are relatively large organic compounds made of amino acids arranged in a linear chain and joined together between the carboxyl atom of one amino acid and the amine nitrogen of another. This bond is called a peptide bond. The sequence of amino acids in a protein is defined by a gene and encoded in the genetic code. There are twenty different amino acids, each with their own properties.
Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of all living organisms and participate in every process within cells. Many proteins are enzymes that catalyze biochemical reactions, and are vital to metabolism. Other proteins have structural or mechanical functions, such as the proteins in the cytoskeleton, which forms a system of scaffolding that maintains cell shape. Proteins are also important in cell signaling, immune responses, cell adhesion, and the cell cycle. Protein is also a necessary component in our diet, since animals cannot synthesize all the amino acids and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that can be used for protein synthesis.
As some of the most commonly studied biological molecules, the activities and structures of proteins are examined both in vitro and in vivo. In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function: for example, enzyme kinetics studies explore the chemical mechanism of an enzyme's catalytic activity and its relative affinity for various possible substrate molecules. By contrast, in vivo experiments on proteins' activities within cells or even within whole organisms can provide complementary information about where a protein functions and how it is regulated.
Objectives of exercise:
• Isolation of proteins by...