Amino Acid Structure and Protein Formation

The foundation of proteins lies in the structure of amino acids. Each amino acid consists of a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group. This R group determines the specific properties of each amino acid.

Vocabulary: Amphoteric - Capable of resisting changes in pH, a characteristic of proteins due to their amino acid composition.

Proteins are formed through condensation reactions between amino acids, creating peptide bonds. This process results in the formation of polypeptides, which can further combine to create complex protein structures.

Example: Glycine, the simplest amino acid, has a hydrogen atom as its R group, while alanine has a methyl group (CH3).

Highlight: There are 20 different naturally occurring amino acids found in proteins, each with a unique R group that contributes to the protein's overall structure and function.

Protein Structure Levels

Proteins exhibit four levels of structure, each building upon the previous:

1. Primary Structure: The sequence of amino acids in the polypeptide chain.
2. Secondary Structure: Regular patterns formed by hydrogen bonding between amino acids, such as alpha helices and beta sheets.
3. Tertiary and quaternary protein structures: The three-dimensional folding of the entire polypeptide chain and the arrangement of multiple polypeptide subunits, respectively.

Definition: Protein sequencing - The process of determining the primary structure of a protein by identifying the order of its amino acids.

Example: The alpha helix is a common secondary structure where the polypeptide chain twists into a regular spiral, stabilized by hydrogen bonds between amino acids.

Highlight: The tertiary structure is responsible for a protein's unique properties and functions, held together by various bonds between the R groups of amino acids.