Structure And Function Of Proteins Essay Aqa Gcse

 
  1. Firstly, I am NOT LOOKING FORWARD to the ESSAY QUESTION!

    Just wondered, if anyone had any tips?

    Also, maybe we could share past questions and think up possible essay questions?

  2. Ive got some title for you to look at..you might want to write it down here so people can correct it

    Synoptic Questions

    1. How the structure of cells is related to their function.

    2. The different ways in which organisms use ATP.

    3. How bacteria affect human lives.

    4. The biological importance of water.

    5. The transfer of energy between different organisms and between these organisms and the environment.

    6. Ways in which different species of organisms differ from each other.

    7. Negative Feedback and its importance in biology.

    8. Condensation and hydrolysis and their importance in biology.

    9. Inorganic ions include those of sodium, phosphorus and hydrogen. Describe how these and other inorganic ions are used in living organism.

    10. Polymers have different structures, they also have different functions. Describe how the structures of different polymers are related to their functions.

    11. Describe how nitrogen-containing substances are taken into, and metabolised in, animals and plants.

    12. Carbon dioxide in organisms and ecosystems.

    13. Why offspring produced by the same parents look different in appearance.

    14. Cycles in Biology.

    15. Describe and explain the uses of genetic engineering in Medical Science.

    16. How the structure of protein is related to their function.

    17. The movement of substances within living organisms.

    18. The structure and function of carbohydrates.


    Maybe start with 9:

    9. Inorganic ions include those of sodium, phosphorus and hydrogen. Describe how these and other inorganic ions are used in living organism.
    (Original post by vixen23)
    Firstly, I am NOT LOOKING FORWARD to the ESSAY QUESTION!

    Just wondered, if anyone had any tips?

    Also, maybe we could share past questions and think up possible essay questions?

  3. (Original post by arvin_infinity)
    Ive got some title for you to look at..you might want to write it down here so people can correct it

    Synoptic Questions


Globular Proteins

  • Molecule forms a coiled shape (globule)
  • Hydrophobic groups point into centre of molecule away from water
  • Only hydrophilic groups are exposed outside the molecule so globular proteins are soluble
  • Globular proteins have roles in metabolic reactions:
    • Enzymes - catalyse metabolic reactions
    • Haemoglobin - binds to oxygen to transport it around body

Haemoglobin

Haemoglobin has a quaternary structure made up of 4 separate polypeptide chains:

  • 2 identical alpha -chains with 141 amino acids each
  • 2 identical beta -chains with 146 amino acids each
  • Each polypeptide chain is folded/coiled into a compact shape due to hydrophobic interactions between the (hydrophobic) R groups
  • All 4 polypeptide chains are linked to form a roughly spherical haemoglobin molecule
  • The precise 3D-shape of the Haemoglobin molecule is absolutely critical to it's Oxygen-carrying function
  • The Hydrophilic R-groups are arranged around the outside of the molecule which allows Haemoglobin to mix with the watery medium inside red blood cells
  • Attached to each polypeptide chain is a prosthetic HAEM group with an Fe2+ ion
  • Each Fe2+ ion can combine with one O2 molecule
  • Human haemoglobin has four polypeptide chains and four haem groups and can therefore carry 4 x O2 molecules
  • When haemoglobin is bound to oxygen it is called oxyhaemoglobin and the colour changes from purplish red to bright red
  • The 3D-shape of globular proteins is critical to their function – slight changes can have radical effects – eg in sickle cell anaemia one amino acid change causes a shape change in the molecule that in turns reduces the ability of haemoglobin to bind to oxygen and changes the shape of the whole red blood cell from a biconcave disk to a sickle shape. Severe sickle cell anaemia can be fatal.

Fibrous Proteins

  • Polypeptides form long chains running parallel to each other
  • These chains are linked by disulphide cross bridges – making the proteins very stable and strong
  • Fibrous proteins have Structural functions:
    • Keratin in skin and hair
    • Collagen - found in bone, cartilage, tendons and ligaments for tensile strength

Collagen

Collagen is the most abundant protein in the animal kingdom. It is found in many diverse organisms and organs:

  • in humans in tendons, the walls of blood vessels, cartilage, bone, gums
  • sea anemones
  • egg cases of dogfish

Collagen is strong but still flexible – this is important in tendons which cannot be rigid

The Primary structure of collagen

  • a repeat sequence of 3 amino acids glycine-proline-X (any other amino acid)

The Secondary/Tertiary Structure of Collagen

  • glycine is the smallest amino acid and this together with proline allow the polypeptide chain to be wound into a tightly coiled, straight and unbranched helix

The Quaternary Structure of Collagen

  • 3 of these helical polypeptides are wound around each other and held by H-bonds.
  • The triple stranded molecules run parallel to others and disulphide cross-linkages between the R-groups of the amino acid lysine holds the molecules together forming fibres
  • The ends of the collagen molecules are staggered to avoid weak points – giving collagen ¼ the tensile strength of steel

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