BIOLCHEM 415 1st Edition Lecture 3 Outline of Last Lecture I. LipidsII. Eukaryotic v. Prokaryotic CellsIII. Organelles in Eukaryotic CellsIV. Thermal Motions power biological interactionsV. Weak Interactions are importantVI. pH is important to maintainOutline of Current Lecture VII. Proteins are linear polymers made of 20 different amino acidsVIII. Amino Acids have different functional propertiesIX. Protein structure: primary, secondary, tertiary, and quaternaryX. Primary structure: the sequence of amino acidsCurrent LectureThe α-amino carboxylic acids can be of 2 stereoisomers- L isomer (S stereochem) - the biologically relevant stereoisomer- D isomer (R stereochem)- have an amine group (NH2) and carboxyl group (COO-)charge of amino acids depend on pH- zwitterionic form-pH 7 - amino acid has both positive and negative charge- NH3+ and COO-Glycine and Alanine- simplest amino acidsThese 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.- Glycine- the simplest- R group = H- only nonchiral amino acid- Alanine - R group = CH3Aliphatic Amino acids- hydrocarbon side chains- Valine- Val, V- C3H7- Leucine- Leu, L- C4H9- Isoleucine- Ile, I - C4H9- Methionine- Met, M- C3H7SProline- cyclic amino acid- aliphatic- C3H6Aromatic Amino Acids- side groups rings with double bonds- Phenylalanine- Phe, F- C7H8- Tyrosine- Tyr, Y- C7H8O- Tryptophan- Trp, W- C9H8NHydroxyl group side chains- Serine- Ser, S- CH3O- Threonine- Thr, T- C2H5O- can form hydrogen bondsCystenine- Cys, C- related to serine- has –SH group- forms weak hydrogen bonds- able to form disulfide bondsBasic Amino Acids- positively charged side groups- side groups contain N- Lysine - Lys, K- C4H11N+- Arginine- Arg, R- C4H11N3+- Histidine- His, H- C4H5N2+- side group is a ringAcidic Amino Acids- have carboxyl groups- Aspartate - Asp, D- C2H2O2-- Glutamate- Glu, E- C3H4O2-- Carboxamid derivatives- non ionizable side chains- can form hydrogen bonds- Asparagine- Asn, N- C2H4ON- Glutamine- Gln, Q- C3H6ONNonessential Amino Acids- synthesized in humans- Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, Pro, Ser, TyrEssential Amino Acids- not generated in humans- must be in our diet- His, Ile, Leu, Lys, Met, Phe, Thr, Trp, ValProtein Structure- primary, secondary, tertiary, and quaternary Primary Structure- sequence of amino acids in a protein- short polymers are called a peptide- first residue has free amine group - last residue has free carboxyl groupPeptide bonds form through condensation reactions- between carboxyl and amine group- a water molecule is released when the bond is formedDisulfide bonding- create crosslinks between polypeptide chainsTrans configuration favored for almost all peptide bonds- trans: Cα groups on opposite sides- cis: Cα groups on the same side- causes steric clashesPsi (Ψ) v. Phi (Φ) Angles- torsional angles in peptide chains- Ψ: Cα-C bond- Φ: Cα-N
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