Lecture+2

Lecture+2 - Lecture 2 Polymers Chains of molecules Mer =...

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Lecture 2 (4/5/12) Polymers Chains of molecules. Mer = part. Monomer: single part. Dimer: two parts. Trimer: three parts. The building blocks of polymers are the monomers. Proteins Amino acids monomers are the building blocks for polypeptides. One or more polypeptides, make up a protein Amino acids are flexible building blocks consisting of two parts: a variable side chain (R- group) and a common group R is an abbreviation representing a molecular subpart often repeated in different molecules or variable between otherwise identical molecules (such as used in amino acids) structure: R-CNH 2 -COOH The basic structure of an amino acid ionization of amino acid: both the -NH2 and the -COOH can ionize as follows: R-NH2 + H+ <-> R-NH3+, and R-COOH <-> R-COO-. The first rx takes H+ from the solution (thus is behaves as a base), the second releases H+ into the solution (thus behaves as an acid) R-group (=side chain). It comes in many shapes and properties: acidic, basic, polar = hy- drophylic, non-polar=hydrophobic, small, bulky (see image further down). There are twenty amino acids Examples: Aspartic acid, Asp, D: R-c-cooh; Asparagine, Asn, N: -c-conh2(*), Cys, C: R-c-sh, Phe, F: R-c-ring peptide bond , formation = amino group of one amino acid reacts with carboxyl group of other, properties. -CNH2-COOH + -CNH2-COOH = NH2-C- CO-NH -COOH Structure of proteins primary: the sequence of amino acids that are "joined' together to form the polypeptide. Note the amino-terminal end, and the carboxy-terminal end secondary the type of amino acid in the chain (primary sequence) determine what secondary structure the polypeptide will form alpha helix: a coiled, spring-like structure stabilized by H-bond between C=O and N-H of close chain members. - 1 -
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Left: Alpha helix. a) turn pattern; b) backbone atoms; c) R groups and H- bonds. Right: pep- tide bond beta pleated sheet: parallel polypeptides form a plate stabilized by H-bond between C=0 and N-H of adjacent chains.
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Lecture+2 - Lecture 2 Polymers Chains of molecules Mer =...

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