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ch369_sp11_class_6_notes

ch369_sp11_class_6_notes - Class web page Some vocabulary...

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Class web page.
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Some vocabulary Proteins - long chains of a.a. with well-defined structures. Peptides - smaller chains of a.a. with flexible structures. dipeptide = 2 amino acids linked together. tripeptide = 3 amino acids linked together. N-terminus = the amine end of the first a.a. in a protein or peptide. C-terminus = the carboxyl end of the last a.a. in a protein or peptide.
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Primary, secondary, tertiary, quaternary structure of proteins. Primary structure is just the a.a. sequence. Secondary structure describes which parts of the protein are helices, turns extended strands, etc. Tertiary structure describes 3-D fold.
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Quaternary structure describes the arrangement of “subunits” in proteins with more than one peptide chain. (each peptide chain is one subunit). Example: Hemoglobin is a “tetramer”, with 4 peptide chains. “Quaternary structure” describes how the 4 peptide chains are arranged. Hemoglobin tetramer, with 4 peptide chains. Two bound heme groups are visible, in red.
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Some peptide examples - Insulin, aspartame. Insulin - 51 amino acid peptide. Aspartame - a dipeptide of aspartate and phenylalanine with an extra methyl group. From aspartame wiki.
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What stabilizes proteins into a specific shape? 1) Mostly hydrophobic a.a. on the inside, and hydrophilic a.a. on the outside. 2) Also, hydrogen bonds between amino acids within in the protein.
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What stabilizes proteins into a specific shape? 3) favorable interactions between positive and negative charged a.a. are common.
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4) Some (not all) proteins contain disulfide bonds between cysteine side chains (yellow), that can stabilize proteins into a well-defined shape.
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For example: “P53 protein” is a DNA-binding protein (its important in coordinating repair of damaged DNA). Protein structure determines function. The shape of the P53 protein recognizes and binds to specific sequences of DNA.
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“Protein folding” Proteins are synthesized in an unfolded form by ribosomes.
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