Bio 200 - Bio 200 Lecture 2: DNA => RNA => Protein...

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Bio 200 Lecture 2: DNA => RNA => Protein Shape is important in protein function Amino Acids: D and L isomers, L most common - amino group, carboxyl group, alpha center, hydrogen atom, and side chain hydrophilic, hydrophobic, and special amino acids Proteins : - Function is derived from the three-dimensional structure, and the three dimensional structure is specified by the amino-acid sequence - Three-dimensional structure = conformation Hierarchical structure of proteins: - Primary - amino end, carboxyl end - Secondary - Folding of localized regions of a polypeptide chain o Stabilizing noncovalent interactions forming, for instance, alpha helices, beta sheets, and beta turns o No noncovalent interactions = random coil o Alpha helix – R groups point outward o Beta sheet – laterally packed, H – bonding between beta strands, pleated, R groups point outward, parallel or antiparallel o Beta turn – H bonds form turn - Motifs: combinations of secondary structures o Fibrous proteins, Ca2+ binding proteins, RNA and DNA binding proteins - Tertiary - Long range folding within a polypeptide chain o Stabilized by hydrophobic interactions between nonpolar side chains, hydrogen bonds between polar side chains, and disulfide bonds between cysteine residues o Provide a compact structure of alpha helices, beta sheets and turns - Domains- o Structural Domain – A region of the protein which is self-stabilizing and can fold independently. o Functional Domain – A region of the protein that exhibits a particular activity - even when isolated from the rest of the protein - Quaternary – proteins assemble with like proteins, multimeric interactions Supramolecular Structure - Macromolecular assemblies - Usually >1 mega daltons in size 10’s to 100’s of polypeptide chains (as well as other macromolecules) Lecture 3:
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Structure of Nucleic Acids: RNA = ribonucleic acid - <100 to 1000’s of nucleotides long DNA = deoxyribonucleic acid - as long as several hundreds of millions of nucleotides long - lacks hydroxy group Purines: - Adenine, Guanine Pyrimidines: - Uracil, Thymine, Cytosine Nuclesides: - nucleotides that do not have a phosphate group End Bias: two ends different from one another - found in both nucleic acids and polpeptides Double helix: - antiparallel arrangement of strands, have end bias - A double bond to T, G triple bond to C - Most DNA is a right-handed helix - B form: two helical grooves => major and minor grooves allow DNA-binding proteins to interact with the double helix, most common conformation - A form: in low humidity the B form changes to A DNA, (RNA-DNA and RNA- RNA helices exist in the A form) - Z form: adopt the left-handed helix conformation, much narrower, Z DNA is also transiently formed shortly after transcription and, as such, is a tag for actively transcribed genes. -
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This note was uploaded on 12/25/2011 for the course BIOL 200 taught by Professor Bureau during the Fall '06 term at McGill.

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Bio 200 - Bio 200 Lecture 2: DNA =&gt; RNA =&gt; Protein...

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