Biology Chapter 5: Proteins

- proteins account for more than 50% of the dry mass of most cells- functions include: structural support, storage, transport, communications, movement and defense- consists of polypeptides that are polymers of 20 amino acids

Enzymes, most of which are proteins

- acting as catalysts, chemical agents that selectively speed up chemical reactions without being consumed by the reaction- because an enzyme can perform its function over and over again, these molecules can be thought if as workhorses that keep cells running by carrying out the processes of life

Polymers of amino acids

A biological functional molecule that consists of one or more polypeptides, each folded and coiled into a specific 3D structure

- all share a common structure- an organic molecule possessing both an amino group and a carboxyl group- amino acids differ in their side chains, called R groups

- at the center of the amino acid is an asymmetric carbon atom called the alpha carbon- its 4 different partners are an amino group, a carboxyl group, a hydrogen atom, and a variable group symbolized by R (also called the side chain, differs with each amino acid)

- the unique characteristics of a particular amino acid- thus affecting its functional role in a polypeptide

S

S

S

S

- when two amino acids are positioned so that the carboxyl group of one is adjacent to the amino group of the other - by a peptide bond

- type of covalent bond- repeated over and over, the process yields a polypeptide

A polymer of many amino acids linked by peptide bonds