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PROTEINS PowerPoint Presentation

PROTEINS

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PROTEINS

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Presentation Transcript

  1. PROTEINS INTRODUCTION

  2. Useful Proteins • There are thousands and thousands of different combinations of amino acids that can make up proteins and that would increase if each one had multiple shapes • Proteins usually have only one useful conformation • Natural selection has eliminated proteins that do not perform a specific function in the cell

  3. Functions / importance of Proteins Type Examples • Structural tendons, cartilage, hair, nails • Contractile muscles • Transport hemoglobin, albumin • Storage ferritin • Hormonal eg. insulin, growth hormone • Enzyme eg. hydroxylases • Protection immunoglobulins • Energy 4.1 k.cal/gm Motor • Signalling • Receptors • Motor proteins kinesin

  4. Protein FamiliesEnzymes • Have similarities in amino acid sequence and 3-D structure • Have similar functions such as breakdown proteins but do it differently

  5. Proteins at Work • The conformation of a protein gives it a unique function • To work proteins must interact with other molecules, usually 1 or a few molecules from the thousands to 1 protein • Ligand – the molecule that a protein can bind • Binding site – part of the protein that interacts with the ligand • Consists of a cavity formed by a specific arrangement of amino acids

  6. Ligand Binding

  7. Enzymes as Catalysts • Enzymes are proteins that bind to their ligand as the 1st step in a process • An enzyme’s ligand is called a substrate • May be 1 or more molecules • Output of the reaction is called the product • Enzymes can repeat these steps many times and rapidly, called catalysts

  8. Enzymes at Work • Lysozyme is an important enzyme that protects us from bacteria by making holes in the bacterial cell wall and causing it to break • Lysozyme adds H2O to the glycosidic bond in the cell wall • Active site is a special binding site in enzymes where the chemical reaction takes place

  9. Antibodies • Y-shaped molecules with 2 binding sites at the upper ends of the Y • The loops of polypeptides on the end of the binding site are what imparts the recognition of the antigen • Changes in the sequence of the loops make the antibody recognize different antigens - specificity

  10. Antibodies

  11. Antibody Family • A family of proteins that can be created to bind to almost any molecule • Antibodies (immunoglobulins) are made in response to a foreign molecule ie. bacteria, virus, pollen… called the antigen • Bind together tightly and therefore inactivates the antigen or marks it for destruction

  12. Motor Proteins • Proteins can move in the cell, say up and down a DNA strand but with very little uniformity • The hydrolysis of ATP can direct the the movement as well as make it unidirectional • The motor proteins that move things along the actin filaments or myosin

  13. Protein Machines • Complexes of 10 or more proteins that work together such as DNA replication, RNA or protein synthesis, trans-membrane signaling etc. • Usually driven by ATP or GTP hydrolysis