BCHM 307 1st Edition Lecture 3 Outline of Last Lecture I Oxidation levels A Definition of Oxidation II Hydrophilic and Hydrophobic Molecules A Definition of Hydrophilic B Definition of Hydrophobic C Definition of Hydrophobic Interactions III IV V VI The Hydrophobic Effect Amphiphilic Molecules in Water The Equilibrium Constant and pH Acid Dissociation Contant and pKa A Definition of Conjugate Base VII Buffers Outline of Current Lecture I Amino Acid Basics A Amino Acid Structure II Amino Acid Characteristics A Definition of Chiral B Definition of Enantiomers III Amino Acid List and Abbreviations A Amino Acid Groups Current Lecture Amino acids are the basic building blocks of proteins There are 20 amino acids in biology All amino acids have the same basic structure They contain a protonated amino group an ionized carboxyl group and a central carbon attached to a hydrogen The variable R group is what gives the amino acid its unique nature and properties Almost all amino acids are chiral Chiral refers to having four different substituents attached to the central carbon atom making them non superimposable The exception is glycine which has a hydrogen R group The chirality gives way to two different stereoisomers Many amino acids are enantiomers Enantiomers are mirror images of each other a specific type of stereoisomer In biology enzymes have stereospecific binding sites for only 1 of the stereoisomers Enantiomers can be either L or D Proteins are made from the L kind These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Amino acids and their respective abbreviations are given below in a table Name Glycine Alanine Valine Leucine Isoleucine Methionine Phenylalinine Proline Serine Threonine Cysteine Asparagine Glutamine Tyrosine Tryptophan Aspartate Glutamate Histidine Lysine Arginine Abbreviations Gly G Ala A Val V Leu L Ile I Met M Phe F Pro P Ser S Thr T Cys C Asn N Gln Q Tyr Y Trp W Asp D Glu E His H Lys K Arg R Amino acids can be put into three categories based on their R group properties The hydrophobic group are those with nonpolar bonds often C C and C H They avoid water interaction and water will form a shell around these In this group are alanine valine leucine isoleucine proline methionine phenylalanine tryptophan and glycine Polar uncharged amino acids can t accept or donate a proton in a solution at physiological pH Amino acids in this group include serine threonine cysteine tyrosine asparagine and glutamate The polar charged group include aspartate glutamate lysine and arginine Histidine can either be in group 2 or 3 It is dependent on the environment s pH Some amino acids have special characteristics Glycine is the only one without a chiral center Proline s R group forms a rigid backbone It prevents rotational flexibility around the amino group It will form a kink in a polypeptide chain Methionine is often used to initiate a polypeptide chain Leucine and Isoleucine have the same mass Below are the structures of amino acids covered in this lecture Only the R groups are written out the basic structure is designated as X
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