Lecture_6_DulaiS09_Proteins

Lecture_6_DulaiS09_Proteins - Lecture 6 Agenda: The...

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1 Lecture 6 Agenda: The molecules of life I – Proteins, Nucleic Acids! 2. What are nucleotides and nucleic acids? What roles do they play in organisms? 1. What are proteins? What determines how a protein works (functions)? Why are they so important?
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2 PROTEINS
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3 Proteins • Made from building block – amino acids • 20 natural amino acids
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4 Tyr Ser Phe Pro N C A polypeptide is a polymer of amino acids A protein consist of one or more polypeptides In polypeptides, amino acids are arranged as “beads” on string All amino acids have a common structure, differing only in the variable “R group.” • The properties of each AA (non-polar, polar, positively charged, negatively charged, etc.) are determined by the “ R group .” • There are 20 commonly occurring amino acids (eight are “essential” in human diet). •Not all amino acids are included in proteins (e.g., GABA, a very important neurotransmitter). R Ala Leu Arg Met N C
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5 Amino acids link together via a condensation reaction to form the peptide bond H H N H O OH C C R H H N H O OH C C R H H N H O C C R N H O OH C C R H H 2 O
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6
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7 Primary Structure Primary Structure Protein structure is organized into a hierarchy of four levels of description Linear sequence of amino acids KNPDKHLEAGCDLLKQAFARAAILSNEKFRGVR Each letter denotes an amino acid: (A = Ala = Alanine; S= Ser = Serine; etc.) • Average protein (polypeptide) has ~500 amino acids • Longest protein (polypeptide) found in nature: ~33,000 amino acids. • Smallest (folding) proteins (polypeptides) found in nature: ~50 amino acids. • Primary structure influences protein shape by allowing some R groups to interact (through Hydrogen bonds).
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8 Secondary Structure Secondary Structure Protein structure is organized in a hierarchy of four levels of description
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This note was uploaded on 11/18/2010 for the course SS 101 taught by Professor Denver during the Spring '10 term at Alabama.

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Lecture_6_DulaiS09_Proteins - Lecture 6 Agenda: The...

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