Globular & Fibrous Proteins
Biology: Cambridge International A Level, topic 2.3.4
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.
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.
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.
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.
Structure of fibrous proteins
- Fibrous proteins are long and narrow.
- Unlike globular proteins, they are insoluble in water.
Functions of fibrous proteins
- The roles of fibrous proteins are to offer structural support to cells.
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.
Test yourself on Globular & Fibrous Proteins
What is Elastin?