lecture notes-biochemistry-1-AAs-proteins

lecture notes-biochemistry-1-AAs-proteins - Analysis of...

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Analysis of Biological System Despite of all their complexity, an understanding of biological system can be simplified by analyzing the system at several different levels: Cell level: microbiology, cell biology; Molecular level: biochemistry, molecular biology ; Population level: microbiology, ecology; Production level: bioprocess.
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Biochemistry Introduction of the biological system at molecule level. This section is devoted mainly to the structure and functions of biological molecules.
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Outline of Biochemistry Section Contents-Cell construction Protein and amino acids Carbohydrates Lipids, fats and steroids Nucleic acids, RNA and DNA Requirements: Understand the basic definitions, characteristics and functions of these biochemicals.
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Amino Acids and Proteins Proteins are the most abundant molecules in living cells, constituting 40% - 70% of their dry weight. Proteins are built from α -amino acid monomers. Amino acid is any molecule that contains both basic amino and acidic carboxylic acid functional groups.
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Amino Acids C R H COOH H 2 N α-amino acid are amino acid in which the amino and carboxylate functionalities are attached to the same carbon, the so-called α– carbon. They are the building blacks of proteins. Where "R" represents a side chain specific to each amino acid. Amino acids are usually classified by properties of the side chain into four groups: acidic, basic, hydrophilic (polar), and hydrophobic (nonpolar). α
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Zwitterion is an amino acid having positively and negatively charged groups, a dipolar molecule. C R H COO - H 3 N + C R H COO - H 2 N C R H COOH H 3 N + +H + -H + +H + -H + Zwitterion Amino Acids
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Isoelectric point (IEP) is the pH value at which amino acids have zero net charge. IEP varies depending on the R group of amino acids. At IEP, an amino acid does not migrate under the influence of an electric field. Amino Acids pH effect on the charge of amino acids We can arbitrarily control the pH of an aqueous solution containing amino acids by adding base or acid. The equilibrium reactions for the simple amino acid (HA) are HAH + = H + +AH (1) HA = H + +A - (2)
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pH effect on the charge of amino acids The proton dissociation constants are K 1, K 2 ] [ ] ][ [ 2 HA H A K + - = (3) ] [ ] ][ [ 1 + + = HAH H HA K (4) [ ] represents concentration in dilute solution. Amino Acids Taking the logs of equations 3 and 4, yields, ] [ ] [ log 1 + + = HAH HA pK pH (5) ] [ ] [ log 2 HA A pK pH - + = (6) where pH=-log(H + ), pK 1 =-log(K 1 ), and pK 2 =-log(K 2 ).
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Standard amino acids : there are 20 standard amino acids that are commonly found in proteins.
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Amino Acids Essential amino acids
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This note was uploaded on 02/13/2012 for the course CHM 3210 taught by Professor Kennell during the Fall '11 term at University of Florida.

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lecture notes-biochemistry-1-AAs-proteins - Analysis of...

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