BCHM 3050 Lecture 7 Outline of Last Lecture I Significance of the Asymmetric Carbon II Essential vs Non Essential Amino Acids III Peptide Bond Formation IV Oxidation Reactions V Schiff s base VI Non standard Amino Acids Outline of Current Lecture I Protein Structure a Primary b Secondary c Tertiary II Mutations III Protein Classification IV Torsion Angles Current Lecture I Protein Structure a Primary i Peptide bonds are very strong and are almost as strong as double bonds ii The specific amino acid sequence of the protein iii DNA dictates proteins b Secondary 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 i Secondary structures alpha helix 1 Hydrogen bond formed between CO and NH backbone 2 Hydrogen bonds connect the first and fifth amino acids i 4 3 Glycine and proline avoid alpha proteins they are helix breakers 4 More alpha helices in nature always have phi around 57 and psi around 47 5 Left handed alpha helices are very rare 6 i 4 is the most common amino acid where the 1st and the 5th amino acids make hydrogen bonds ii Beta sheets are the second type of secondary structure that amino acids form 1 N to C terminus in one direction N to C terminus in the opposite direction antiparallel 2 Hydrogen bonds are stronger in antiparallel sheets than parallel sheets iii Twisted mix of parallel and antiparallel beta sheets in the same strand iv Beta alpha beta is a supersecondary structures v Loops and turns are positions where you break a helix vi Turns connected one beta sheet to another vii Glycines and prolines are helix breakers c Tertiary i Tertiary structures are a group of secondary structures ii Formed by R group interactions iii Interactions that stabilize tertiary structures 1 Hydrophobic interactions 2 Electrostatic interactions 3 Hydrogen bonds 4 Covalent bonds II Mutations a without mutations we wouldn t evolve b People with sickle cell anemia have a valine where a glutamic acid should be in position 6 completely getting rid of the negative charge of the acid c This started out in Africa people adapted and the mutation started III Protein Classification a Classify proteins based in globular or fibrous b Fibrous structural insoluble c Globular functional soluble d Glycoproteins are attached to the surface e Amino acids joined by peptide bonds f IV R groups do not have a role in the primary structure Torsion Angles a Peptide bonds is between an amino group and a carboxylic acid b Phi refers to the bond rotation between the alpha carbon and the nitrogen c Psi bond rotation between alpha carbon and carbon 1 d Proteins are defined by their phi and psi values e Omega bond contortion between carbon 1 and other nitrogen f Phi psi and omega determine how the protein will look in the end
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