Protein Structure, Digestion,

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  1. What is an example of a quaternary level of structure?
    Human hemoglobin has four subunits, tretramer.

    Protein kinase is also a tetramer.
  2. Six examples of permanent chemical groups that associate with proteins?
    • Lipoproteins
    • Glycoproteins: IgG
    • Phosphoproteins
    • Hemoproteins: Hemoglobin
    • Flavoproteins: Flavin nucleotides
    • Metalloproteins: Iron, Ca, Copper
  3. Important initial facts how Amino Acids get into bloodstream?
    • -First must go through enterocytes (cells that line the small intestine) at the brush border, which line the small intestine lumen.
    • - Need to be coupled with Sodium, NA to enter into the cell, with the help of a "carrier", "transporter".
    • -The carrier is called a symport because it transports the AA simultanously with the NA.
    • - Sodium potassium pump is necessary to pump the "excess" sodium back OUT of the cell.
  4. How are dipeptides and tripeptides transported into the cytosol of the enterocyte?
    Next step once inside?
    Dipeptides and tripeptides must be co-transported with a "proton" (hydrogen)

    Once in the cytosol of the cell, they are catabolized into amino acids.

    The excess H protons are transported out with a Sodium, Hydrogen antiport.
  5. Activity at the Basolateral membrane of the enterocyte?
    Some of the amino acids that were broken down from the di and tripeptides need to be co-transported out with sodium through a facilitated carrier.

    There is a Sodium/Potassium pump on the enterocyte's basolateral membrane to bring potassium in and sodium out.
  6. What are the characteristics of Globular Proteins?
    • Globular - water soluble
    • - spherical
    • - Complex interactions between secondary and tertiary structural elements
  7. Give four examples of globular proteins
    • 1) Enzymes (kinase), biological catalyst
    • 2) Hormones (insulin), regulate biological processes
    • 3)Transport (albumin), carry molecules in plasma
    • 4) Storage (ferratin) store and protect
  8. What are the characteristics of fibrous proteins?
    Fibrous proteins are animal structural materials and water insoluble.

    Unique structures obtained by combining special amino acids into regular, secondary structural elements.
  9. Give three examples of fibrous proteins in humans.
    • 1) Collagens
    • 2) Keratins
    • 3) Elastins
  10. Characteristics and facts about collagens?
    Collagen is the MOST ABUNDANT protein in the body.

    Forms connective tissue: bones, tendons, ligaments, cartilage.
  11. Examples of keratin in the body?
    Keratin makes up protective tissue, such as skin, hair, nails.
  12. Examples of where elastin proteins are in the human body.
    Elastin can be found in:

    • - Aorta
    • - Large arteries
    • - Ligamentum flavum
  13. Describe collagen construction
    • Triple helix, about 1000 amino acids long
    • Most abundant protein
    • Glycine makes 1/3 of collagen
    • Very strong hydrogen bonding between polypeptide chains because of small size of glycine, increases hydrogen bond strength
  14. What are examples of Type I Collagen?

    Hallmark characteristic of this type?
    Type 1: Has tensile strength

    • - Skin
    • - Bone
    • - Ligaments
    • - Tendons
  15. Examples of Type II Collagen and characteristic
    Type II: Resists compression

    • - Cartilage
    • - Intervertebral disk
  16. Example of Type III Collagen?
    Blood vessel walls
  17. Example of Type IV Collagen?
    Found in the basement membrane of cells.
  18. In the biosynthesis of collagen, how is the collagen formed, and where?
    Collagen is formed by fibroblasts and secreted into the extracellular matrix
  19. What is the (repeated) sequence of the polypeptide of collagen?
    • Glycine-Proline- a) hydroxyproline
    • b) hydroxylysine

    ( a and b are Derived Amino Acids ONLY found in collagen)
  20. What are the two enzymes needed to put hydroxyl groups on prolyl residues?
    • Prolyl hydroxylase
    • Lyso hydroxylase

    (hydroxylase is enzyme that helps to form the bond between the OH group and proline)
  21. What is the cofactor necessary to put the hydroxyl group on prolyl residues
    Need ascorbate acid, Vitamin C, to hydroxylate prolyl
  22. What is Scurvy and it's symptoms.
    • Scurvy: deficiency of ascorbic acid, vitamin C
    • Tensile strength of collagen fibers can't connect, "cross link" as well due to lack of hydrogen bonding

    • -Sore spongy gums
    • - Loose teeth
    • - Fragile blood vessels
    • - Bruises
    • - Anemia
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Protein Structure, Digestion,
Pg. 48
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