Biology 1020 lecture 5 Biological Molecules B

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  1. Proteins do work in cells
    • 3D folded and coiled molecules - structure fits function
    • 50% of the dry mass of cells
    • 1+ polypeptides
  2. Functions of Proteins
    • Provide support (keratin and collagen)
    • Move cells, organelles ( muscles - actin and myosin)
    • Assist chemical reactions (enzymes)
    • Store amino acids (e.g. ovalbumin)
    • Protect against disease (antibodies)
    • Co-ordinate activities (hormones)
    • Transport materials between cells (hemoglobin)
    • Allow cells to detect and respond to stimuli-receptors on cell surfaces
  3. Protein structure
    • polymer: polypeptide
    • monomer: amino acids
    • ** 50-34000 amino acids long peptide
  4. Amino acid structure
    • central alpha carbon
    • carboxyl and amino group
    • side chain/variable groups - R group
  5. Amino acids
    • grouped based on properties of R groups at pH 7.2
    • Uncharged
    • - polar
    • - uncharged

    • Charged
    • - Acidic
    • - Basic
  6. Amino Acids are catergorized characteristics
    Amino Acids (ex. Aspartic or Glutamic acid): They have a carboxyl group on their side chain that can donate a H+

    Amino Bases (ex. Lysine, Arginine, Histidine): They have a nitrogen group on their side chain that can accept H+

    Non-Polar Amino Acids (ex. Tryptophan and Glycine): They have lots of hydrocarbon bonds that are non-polar on their side chains.

    Polar Amino Acids (ex. Serine): They have hydroxides, disulfide, and/or NH2-C=O group on side chain.
  7. Polypeptides
    Amino acids are held together in polypeptides by peptide bonds formed via a dehydration reaction between the carboxyl and the nitrogen groups on the main backbone of the amino acid.
  8. Protein Shape
    • Order and properties of amino acids determine shape
    • Activity/function in a particular region (action site of protein)
    • Other molecules bind/fit into a specific  space
  9. Protein Shape #2
    • Starts to fold into shape as it is synthesized
    • Physical interactions assist folding
    • aqueous environment
    • e.g. non-polar amino acids shielded from water
    • parts of the chain brought close together
  10. Levels of structure of a protein
    • Primary
    • Secondary
    • Tertiary
    • Quaternary (most folded)
  11. Protein Primary Structure
    • Unique sequence of amino acids
    • Determined by the gene sequence
    • (Just the sequence of "beads" on a necklace. Amino acids).
  12. Protein Secondary Structure #1
    • Coils or folds in polypeptide
    • Hydrogen bonds between different parts of polypeptide backbone. O-ve  H+ve
    • properties determined by mix of structure
  13. Protein secondary structure #2
    α helix: Proteins rich in alpha helical structures tend to be fibrous and strong.

    β pleated sheet: Proteins rich in beta sheets tend to stretch and recoil.
  14. Protein Tertiary Structure
    • Hydrophobic amino acids shield from water
    • R groups close together for H bonding
    • Disulfide bridges
    • * Covalent bond. -S-S- cysteines
  15. Protein Quaternary Structure
    • 2+ polypeptide chains form one molecule.
    • Can be Globular (e.g. hemoglobin, 2 beta and 2 alpha chains), or Fibrous (e.g. collagen - 3 polypeptides coiled)
  16. Protein structure affected by...
    • pH
    • Solute Concentration
    • Temperature
  17. Loss of Protein Structure
    • Protein is denatured when it has lost proper 3D structure and loses function
    • Denatured proteins can aggregate in harmful ways in cells.
    • In some cases, the denatured protein can be renatured to a normal protein.
  18. Protein (re)folding: Chaperonins
    • Stressors such as heat can cause a protein to unfold
    • Chaperonins assist the proper folding/refolding of other proteins.
    • Chaperonin consists of a cap and a hollow cylinder
  19. Small changes to protein structure affect function: Sickle cell hemoglobin
    • Inherited blood disorder, Sickle-cell disease
    • Single amino acid substitution in hemoglobin
    • Glutamine-polar becomes Valine-non polar
    • changes primary level to quarternary level
  20. Prions
    • Infectious proteins
    • * Mammals
    • * Fungi
    • Abnormally folded, Not denatured by most denaturants such as heat, radiation, etc.
    • Cause normal proteins to lose their structure
    • - infectious
  21. Nucleic Acids
    • DNA - Deoxyribonucleic Acid
    • RNA - Ribonucleic Acid
  22. Passing of information
    • Synthesis of mRNA in the nucleus (transcription)
    • Movement of mRNA into cytoplasm via nuclear pore
    • Goes to ribosome. Synthesis of protein (translation)
  23. Nucleic Acid: Monomers
    Called Nucleotides: Nucleoside (nitrogenous base and pentose sugar) and phosphate.
  24. Pyrimidines
    • Single ringed
    • Cytosine
    • Thymine
    • Uracil
  25. Purines
    • Double ringed
    • Adenine
    • Guanine
  26. Polynucleotide Structure
    • Sugar-phosphate backbone
    • - Covalent bond
    • - OH on #3 carbon of one sugar
    • - Phosphate on #5 carbon

    • Nitrogenous bases as appendages
    • Forms helix structures
  27. DNA double helix
    • 2 polynucleotide spiral around an axis
    • Backbones run in opposite directions
    • => anti-paraellel
    • 5'--> 3'
    • 3'--> 5'
    • H bonds between. Nitrogenous bases: A-T and G-C
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Biology 1020 lecture 5 Biological Molecules B
2013-10-02 06:14:13
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