PROTEINS

PROTEINS

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  • Created by: EClou
  • Created on: 07-01-15 23:26
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  • PROTEINS
    • structural components
    • Membrane carriers and pores e.g AT and FD
    • enzymes, hormones and   antibodies
    • Amino Acids = monomer
      • contain one acid end (e.g. COOH) and one amino end (e.g. NH2)
      • 20 types
      • R1=H=glycine R2=CH3=Alanine R3= C3H7=Valine
      • central C atom with 4 bonds to hold together 2 ends, an H atom and the R group
      • the link between AAs are called PEPTIDE BONDS and are formed by condensation reactions
        • linked during protein synthesis in ribosomes
        • forms a  POLYPEPTIDE CHAIN
        • broken by hydrolysis reactions
      • DEAMINATION = how  surplus AAs are removed form animal's bodies
        • excess AAs become Toxic
      • 2 AAs =  DIPEPTIDE bond
    • Structures
      • Primary
        • the sequence of AAs in the polypeptide chain
      • Secondary
        • polypeptide chains can fold into shapes depending on H bonds formed between the AAs
          • if  Alpha helix it COILS
          • if Beta helix it PLEATS
      • Tertiary
        • further folding due to interaction betwn. AAs
        • IONIC interactions: weak attractions betwn. pos.+neg. charges
        • H bonds
        • DISULPHIDE bonds: form betwn. SH groups on side group of Cysteine = covalent + strong
        • HYDROPHOBIC + HYDROPHILIC: -phob- groups are close they clump, when -phil- groups are close they push apart
    • The breakage of Peptide bonds is catalysed by PROTEASE
    • Shape relates to function
      • Collagen
        • Fibrous protein that that form supportive tissues and therefore must be strong
        • 3 polypeptide chains tightly coiled in tripl helix
        • insoluble
        • metabolically unreactive
        • repeating AA sequence
      • Haemoglobin
        • Globular protein with haem iron group that binds to O2 for transport
        • roles up into ball-like structure
          • means hydropilic on outside and hydrophobic on inside
        • non-repeating AA sequence
        • soluble and metabolically active
        • 2 alpha + 2 beta chains

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