Proteins Biochemistry Unit 1

What You Need to Know! How to recognize protein by its structural formula The cellular function of proteins The four structural levels that proteins can go through to reach their final shape (conformation) and the denaturing impact that heat and pH can have on protein structure

Proteins 1.Contain C, H, O, N, S 2.Function: Structural molecules (muscles, cartilage, etc) Enzymes (carry out chemical reactions (Rx)) Antibodies (immune response) Protein hormones (hGH) Membrane embedded transport molecules (blood - hemoglobin) 3.Monomers: 20 different amino acids (AA)

Proteins 4.True polymers: polypeptide Small protein = ~100 AA Large protein = hundreds of AA 5.Proteins are sensitive to temperature pH solutions all cause denaturizing (loss of accurate 3D structure)

Amino Acids Zwitterions: molecules that have both an amino group (NH 3 ) and carboxyl group (COO or COOH) 20 different AA All have the same central carbon, amino group, and carboxyl group Different functional groups (R – side chain) R can be: –Polar, non-polar, charged, uncharged, hydrophilic, hydrophobic

20 Amino Acids

Polypeptides Connecting multiple AA Condensation Reaction forms peptide bond Repetitive peptide backbone

Protein structure (4 stages) Structure and function determined by # and sequence of AA 1.Primary structure (AA sequence) 2.Secondary structure (Hydrogen to Oxygen) Primary polypeptide coil and fold Due to hydrogen bonds between adjacent peptide bonds O   H Special: alpha-helix, beta-pleated sheet

Protein Structure (4 stages) 3.Tertiary Structure (R-side interactions) Further coiling of secondary polypeptide due to R interactions Hydrophobic vs. Hydrophilic Polar Molecules Formation of disulfide-bridge S-S Hydrogen bonds Van der Waals 4.Quaternary structure Some proteins will associate with other tertiary proteins to form quaternary proteins Several tertiary polypeptides connect together; usually held together by R-side chain interactions (hemoglobin)

Structure Animation YQ

Mutations Gene mutations (exchange of one or more nucleic acids, if not silent) can lead to the exchange of one or more AA. This can lead to a non-functional quaternary structure and, therefore, to a non- functional protein Example: Sicle-Cell Anemia, 1 AA is exchanged in the hemoglobin primary structure, resulting in wrong folding.