Chapter 5 - Reginald H. Garrett Charles M. Grisham Chapter...

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Reginald H. Garrett Charles M. Grisham Chapter 5 Proteins: Their Primary Structure and Biological Function
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Chapter 5 “…by small and simple things are great things brought to pass.” ALMA 37.6 The Book of Mormon Although helices sometimes appear as decorative or utilitarian motifs in manmade structures, they are a common structural theme in biological macromolecules – proteins, nucleic acids, and even polysaccharide.
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Essential Question What structural forms do polypeptide chains assume, how can the sequence of amino acids in a protein be determined, and what are the biological roles played by proteins?
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5.1 What Architectural Arrangements Characterize Protein Structure? Proteins are classed according to shape and and solubility Shape - globular or fibrous The four levels of protein structure are: - Primary - sequence - Secondary - local structures - H-bonds - Tertiary - overall 3-dimensional shape - Quaternary - subunit organization
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5.1 What Architectural Arrangements Characterize Protein Structure? Figure 5.1 (a) Proteins having structural roles in cells are typically fibrous and often water insoluble. (b) Myoglobin is a globular protein. (c) Membrane proteins fold so that hydrophobic amino acid side chains are exposed in their membrane-associated regions.
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5.1 What Architectural Arrangements Characterize Protein Structure? Figure 5.2 Bovine pancreatic ribbonuclease A contains 124 amino acid residues, none of which are Trp. Four disulfide bridges are indicated in gold.
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5.1 What Architectural Arrangements Characterize Protein Structure? Figure 5.3 The α-helix and the β-pleated strand are the two principal secondary structures found in proteins. Secondary structures in proteins
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How to view a protein? The tertiary structure of a protein may be viewed in several ways (Figure 5.4): Backbone only Backbone plus side chains Ribbon structure Space-filling structure Each of these is an abstraction
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How to view a protein? Figure 5.4 Folding of the polypeptide into a compact, roughly spherical conformation creates the tertiary level of protein structure.
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The Quaternary Level of Protein Structure Figure 5.5 Hemoglobin is a tetramer consisting of two α and two β polypeptide chains.
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A Protein’s Conformation Can Be Described as Its Overall Three-Dimensional Structure Be careful to distinguish the terms “conformation” and “configuration” A configuration change require the breaking of a bond. A protein, or any molecule, can change its conformation by changing shape without breaking a bond.
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Figure 5.6 Configuration and conformation are not synonymous Rearrangements between configurational alternatives can be achieved only by breaking and remaking bonds.
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Figure 5.6 Configuration and conformation are not synonymous Imagine the conformational possibilities for a protein in which two of every three bonds along its backbone are freely rotating single bonds.
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Purified from Cells?
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This note was uploaded on 10/04/2011 for the course SCIENCE 1001 taught by Professor Staff during the Spring '11 term at LSU.

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Chapter 5 - Reginald H. Garrett Charles M. Grisham Chapter...

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