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Chapter 2- Proteins.docx

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University at Buffalo
Biological Sciences
BIO 203

1 Chapter 2: Proteins Four Levels of Protein Structure Major Protein Function Structural Significance Metabolism – catalyzing chemical reactions • Enzymes are catalysts, or molecules that lower the energy required for a chemical reaction to proceed. • Most enzymes are proteins • Proteins catalyze reactions by binding to reactants Signaling – delivering chemical messages • Proteins serve as both message transmitters and throughout cells and tissues of an organism receivers, linked by structure Transport – carrying molecules throughout the • Proteins transport nutrients, waste products, and body other substances between cells, within cells, and across cell membranes • Each transport protein has a unique structure to bind to a specific substance o i.e. hemoglobin in RBC binds to oxygen to transport it throughout the body Structure – forming organelles and other cell • Proteins provide structural support at several levels- structures as well as the basis of macroscopic structures organelles, cells, and organs Movement – moving substances, cells, and • Protein structure controls contractile and motor body parts functions • Proteins can move substances within cells Defense – defending the body against disease- • Proteins in the immune system such as antibodies causing agents bind to and destroy invasive bacteria and viruses Proteins  Made up of one or more polypeptides Polypeptides  Are chains of amino acids linked together by peptide bonds Primary Structure – amino acids link together to form a linear polypeptide  Primary structure of a protein is a linear chain of amino acids  Amino acid monomer o Composed of a central carbon called the alpha carbon o Alpha carbon bonds to  An amino group  Side chain / R-group  Carboxyl group  Hydrogen atom How does the cell link the amino acids together? • A carboxyl group can bond to an amino group by dehydration reaction – removal of water molecule o Forms peptide bond • Peptide bonds 2 o Covalent bonds of carbon to nitrogen that form after dehydration reaction Secondary structure o Hydrogen bonds between atoms in polypeptide backbone creates a folded or coiled shape o Segments of polypeptide chain form coiled or folded patterns o R-group determine tertiary and quaternary structures • a-helices (Looping coils) o develop from the H-bonds that form between the oxygen of a carboxyl group and the hydrogen of the 4 amino group in the chain • B-pleated sheets (folded patterns) o Form when two or more strands of a polypepti
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