Biological Molecules 1 (MJC)

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Biological Molecules 1 (MJC)
2012-02-14 19:11:13
MJC Biological molecules

Bio molecules
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  1. Draw the structure of alpha glucose and beta glucose.
  2. Draw the formation of a alpha(1,4) glycosidic bond.
  3. Why is starch a good storage molecule?
    • 1) The molecules of starch are compact and takes up a small amount of volume/space, hence a large amount of glucose monomers can be stored in a small volume/space.
    • 2) Since the molecules of starch are large and have no polar groups, it is insoluble in water and hence do not exert osmotic pressure.
  4. Amylose is a carbohydrate in starch that is helical in shape. How is this helical structure maintained?
    The hydroxyl group on carbon-2 of each glucose molecule projects out into the middle of the spiral and forms hydrogen bonds with each other hence stabilising the helical structure of amylose.
  5. Describe the components of a deoxyribonucleotide.
    • Pentose sugar called deoxyribose
    • 4 Nitrogenous bases consisting of purines(2 rings) : adenine, guanine and pyrimidines(1 ring) : cytosine, thymine
    • Phosphate group
  6. State 3 physical properties of collagen that catergories it as a fibrous protein.
    • 1) It does not have a tertiary structure
    • 2) It is insoluble in water
    • 3) It is physically tough/ has high tenile strength

  7. The bonds shown above is a :
    1) Glycosidic bond
    2) Phosphodiester bond
    3) Disulphide bond
    2) Phosphodiester bond

  8. Based on the picture shown above, explain why triglycerides are insoluble in water while the products of their hydrolysis is.
    Triglyceride consists of long hydrocarbon chains with no polar groups, hence it is insoluble in water.

    • The products of hydrolysis of triglycerides are glycerol and 3 fatty acids.
    • Glycerol has 3 hydroxyl groups while one fatty acid has a hydroxyl group (within their carboxyl groups) that can form hydrogen bond with water molecules.

    Hence, they are soluble in water.

  9. State the level of structure shown in the picture above and the bonds found.
    • Level of protein structure: Tertiary structure.
    • Hydrogen bonds
    • Disulphide bonds
    • Ionic bonds
    • Peptide bonds

  10. Which components of the phospholipid give rise to its amphipathic nature?
    The phosphate group is polar and hydrophilic while its 2 fatty acid chains are non-polar and hydrophobic.

  11. Due to the amphipathic nature of phospholipis, it usually form a phospholipid bilayer as shown above. State where this bilayer can be found in a cell and its function.
    • It can be found in the cell membrane.
    • It functions to regulate the entry and exit of subtances into and out of the cell as lipid-soluble/non-polar molecules can pass throught the cell membrane.
  12. What are the bonds found in a cellulose fiber?
    • 1) Beta-1,4 glycosidic bonds between the beta-glucose monomers
    • 2) Hydroxyl groups that project out from both side of the cellulose chain forms hydrogen bonds between the adjacent cellulose chains in a microfibril.
    • 3) Hydrogen bonds between adjacent microfibrils in a cellulose fiber.
  13. Describe the following terms:
    a) Quaternary structure

    b) Tertiary structure
    • a) A quaternary structure is a highly complex protein that consist of an aggregation of two or more extensively coiled polypeptide chains held together by disulphide linkages, ionic bonds, hydrogen bonds and hydrophobic/ hydrophilic interactions between R groups of amino acids
    • b) One polypeptide chain (may consist of both alpha helices and beta sheets) that is further coiled and extensively folded to form a compact three-dimensional globular structure.

  14. Sickle cell anemia is caused by a change in a single amino acid in the polypeptide chain as seen above in Hb S. Explain why the change in one amino acid will result in this disease.
    The change in the amino acid sequence changes the primary structure of the protein which in turns alters the secondary, tertiary and quaternary structure of the protein. This hence results in haemoglobin to adopt a sickle shape, giving rise to anemia.

  15. Identify the structure above and the bonds that stabilise the structure.
    • Alpha-helix
    • The bonds formed are hydrogen bonds between the hydrogen atom of the NH group of one amino acid and the oxygen atom of the C=O group of another amino acid 4 places ahead of it.

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