2.3.4

Globular & Fibrous Proteins

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Globular Proteins

Globular proteins are one of the main classes of proteins. Conjugated proteins are a specific type of globular proteins that contain a prosthetic group.

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Structure of globular proteins

  • Globular proteins usually have a roughly spherical shape.
  • The tertiary structure of these proteins is what leads to their round structure.
    • Van der Waals forces (induced dipole-dipole forces) and hydrogen bonds between different parts of the polypeptide chain help to maintain the coiled structure.
  • Globular proteins are soluble in water.
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Functions of globular proteins

  • Globular proteins can have a number of roles:
    • Messengers - regulation of biological processes by transmitting messages.
    • Enzymes - catalysis of reactions.
    • Structural proteins - some globular proteins that are soluble as monomers can provide good structural support when polymerised.
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Examples of globular proteins

  • Haemoglobin.
    • Haemoglobin is a conjugated protein that carries oxygen around in the blood of humans and most other vertebrates.
    • The prosthetic group is the haem group.
  • Insulin.
    • Insulin is an example of a hormone that acts as a messenger.
    • The role of insulin is to control blood glucose concentration.
  • DNA polymerase.
    • This globular protein functions as an enzyme.
    • The role of this enzyme is to make DNA molecules from nucleotides.

Fibrous Proteins

FIbrous proteins are another of the main classes of proteins.

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Structure of fibrous proteins

  • Fibrous proteins are long and narrow.
  • Unlike globular proteins, they are insoluble in water.
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Functions of fibrous proteins

  • The roles of fibrous proteins are to offer structural support to cells.
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Examples of fibrous proteins

  • Collagen.
    • Roughly 30% of the protein in your body is collagen.
    • Found in ligaments, tendons, muscle, cartilage, bone and skin.
  • Keratin.
    • Keratin is crucial to maintaining the structure of horns, claws, hooves, hair and skin.
  • Elastin.
    • Elastin is found in connective tissue and is what allows our skin to return to its normal appearance after being pinched.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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