Structures of Proteins and Denaturation Presented to you by:Dylan Kutz, Jacob Hare, and CJ Tyler

Primary Structure of Protein Consists of a sequence of amino acids in a chain Each amino acid is comprised of a codon from DNA A codon is made of three nitrogenous bases from DNA The order of amino acids affects the properties of the protein

Primary Structure of Proteins Examples: Human insulin is made of two amino acid chains bonded by disulfide ridges It is necessary to utilize carbs

Secondary Structure of Protein Two Structures: a-helix B-pleated sheet They repeat certain patterns of amino acids Very few proteins have predominantly repeating structures

A-Helix A single protein chain twists to form a helix Shape is maintained by hydrogen bonds All amino acids side chains extend outward from the helix

B-pleated Sheets Occurs when amino acid chains run parallel to each other Shape is also maintained by hydrogen bonds

Random Coil Only have certain portions of their structure in helix or pleated sheet form Possible to have a-helix, b-pleated sheet, and random coil structure at different points in a molecule

Tertiary Structure of Protein 3 dimension arrangement of all atoms in a molecule Unlike secondary structure it contains side chains that are connected to the core structure Stabilized in five ways

5 Ways to Stabilize Covalent bonds: Primarily disulfide ridges. Hydrogen bonds: They bond inter and intra-molecularly. They will join the side chains and the back bone of the molecule. Salt bridges: Occur when to ionized salt chains come together to form salt bonds.

Stabilizing cont’d Hydrophobic interactions: In an aqueous solution proteins group their polar groups outward and their non polar groups inward away from any water molecules. They interact and form bonds that are weaker than hydrogen bonds but act over a large surface area.

Stabilizing cont’d Metal ion coordination: Two side chains that have the same charge that would normally repel each other are linked with a metal ion. This is way the human body needs trace metals because it is necessary to maintain protein structures.

Quaternary Structure of Proteins The highest level of protein organization Have more than one polypeptide chain Determines how all the proteins come together

Quaternary Continued Ex: Hemoglobin: four chains of amino acids. Contains 2 alpha and 2 beta chains Collagen: Comprised of triple helix units called tropocollagen. Stabilized by hydrogen bonding between the 3 chains

Denaturation Any physical or chemical change to a structure of a protein Ex: When cooking an egg with heat the proteins in the egg denature to cook the egg Disulfide ridges in proteins can be broken by 2-mercaptoethanol; reduces them to SH groups