Proteins & Nucleic Acids Images taken without permission from

Proteins: A General Overview Biological roles: enzymes, structural components, hormones, immune function, storage, transport, muscle contraction Monomer = amino acid Polymer = polypeptide chain (protein)

Monomer = amino acid There are 4 components attached to a central carbon There are 20 different amino acids Amino group Central carbon Carboxyl group R group the R group for each amino acid is different  determines its properties hydrogen

Classes/Categories of Amino Acids The R group determines the class/category of an amino acid General categories: –Nonpolar –Polar –Positively Charged –Negatively Charged

Peptide Bonds Formation of a protein occurs when amino acids covalently bond through the formation of a peptide bond. What kind of reaction forms a peptide bond? –Dehydration reaction Peptide bond

Four Levels of Protein Structure Primary Secondary Tertiary Quaternary –Only proteins with multiple chains will have this level of structure All proteins have primary, secondary and tertiary structure

Primary Structure (1°) The sequence of amino acids All other structures are based on this level of structure Primary Sequence of Hemoglobin Chain A: VLSPADKTNVKAAWGKVGAH......etc N terminus C terminus

Secondary Structure (2°) Local helical coiling (alpha helix) or pleated sheet (beta sheet) formations in the chain Patterned formations based on hydrogen bonds between non- adjacent amino acids

Tertiary Structure (3°) The way the polypeptide chain is folded three dimensionally. Is brought about through the following interactions: –Disulfide bridges –Ionic interactions –Hydrophobic interactions –Hydrogen bonds

Quaternary Structure (4°) Interaction between two or more polypeptide chains.

Important Protein Concept Changes in protein structure can lead to disease Ex. Sickle cell anemia = disease caused by a single amino acid substitution in the  chain of hemoglobin Image taken without permission from

Protein Folding Proteins are folded into the appropriate formation during or after protein synthesis Certain conditions such as temperature, pH, and salt concentrations can alter the shape of a protein Chaperonins assist to fold proteins correctly in the cell –Think “chaperones” Denaturation = unfolding of protein

Nucleic Acids Biological roles = Store/carry genetic information, form part of ribosomes, energy carriers Monomer = Nucleotide (A, T, C, G) Polymer = Nucleic Acid –DNA –RNA

Nucleotide Components Consist of 3 parts: Phosphate group 5 carbon (pentose) sugar Nitrogenous base –A, T, C, G, U (RNA only)