Lecture 15.Feb26(2) - BIO 311C Spring 2010 Lecture 15...

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BIO 311C Spring 2010 Lecture 15 – Wednesday 24 Feb. 1
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* Illustration of a Polypeptide amino acids peptide bonds Folding and other modifications Functional Protein Polypeptide (chain) Review 3
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Structural Formula of an Amino Acid A central carbon atom is attached to four chemical groups. The central carbon is an asymmetric carbon atom unless R is identical to one of the other three chemical groups. central carbon atom Both the amino and the carboxylic acid functional group are ionized except at extreme pH values. A single amino acid that is not chemically attached to anything else is called a "free amino acid". Characteristics of Free Amino Acids * 4
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Ways of Showing the Structural Formula of an Amino Acid Uncharged form; does not occur in aqueous solutions at neutral pH. Charged form that occurs in aqueous solutions at near neutral pH. Detailed structure Abbreviated Structure * 5
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H H 3 N COO C R - + The R-group of a few kinds of amino acids carry an amino or a carboxylic acid functional group. These amino acids carry three electrical charges. central carbon atom Amino Acids Used to Construct Proteins * Since the central carbon atom of an amino acid is asymmetrical, there are 2 enantiomers of each kind of amino acid. Cells use only the "L" enantiomer of each kind of amino acid to construct proteins. Twenty different kinds of amino acids are used for constructing proteins, each with a different "R" group. 6
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Aspartic Acid (shown without its functional groups ionized) How many electric charges would this free amino acid have in the cytoplasmic matrix of a living cell? How many asymmetric carbon atoms does this free amino acid contain? Glycine (shown without its functional groups ionized) How many electric charges would this free amino acid have in the cytoplasmic matrix of a living cell? How many asymmetric carbon atoms does this free amino acid contain? * An individual amino acid that is not covalently bonded to another molecule is called a “free” amino acid. So far we have only considered free amino acids.
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This note was uploaded on 06/11/2010 for the course BIO 48765 taught by Professor Sathasvian during the Spring '10 term at University of Texas at Austin.

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Lecture 15.Feb26(2) - BIO 311C Spring 2010 Lecture 15...

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