Fibrous proteins

What molecules do they make?

Strong, long insoluble molecules that don’t fold into complex 3-dimensional shapes like globular proteins

What is there a high proportion of?

Amino acids with hydrophobic R-groups in their primary structures

What do they have a limited range of?

Amino acids, small R-groups meaning primary structure is usually repetitive

What are examples?

Collagen, keratin and elastin

What is collagen?

Fibrous protein where every 3rd amino acid in polypeptide chain is glycine

What forms from 3 polypeptide chains?

They coil to form a left handed helix

What does glycine do?

Allows polypeptide chains to be close together when they twist sue to small R group

How do collagen bonds form?

Between adjacent polypeptide chains, hydrophilic groups on outside of molecule making it insoluble

What else does collagen form?

Fibrils, adjacent molecules joined by cross links with ends of molecules staggered

Where is collagen found?

Skin, artery walls, for strength and insolubility

Why are tendons mostly collagen?

Allow muscles to pull bones

Why are bones formed from collagen?

Reinforced with calcium phosphate

What important component does collagen make?

Cartilage and connective tissue in skin

Where is keratin present?

Hair, skin and nails

What is it mainly made of?

Cysteine (sulphur rich amino acid) forming strong disulphide bridges

What are some properties of keratin?

Strong, inflexible and insoluble

Where is elastin found?

Elastic fibres, small protein fibres, walls of blood vessels and in alveoli

What is a property of elastin?

Flexibility to expand and recoil

What is the structure of elastin?

Quaternary protein made from stretchy molecules called tropoelastin