fibrous and globular proteins

Fibrous proteins

Long parallel polypeptide chains with ocassional cross linkages that form tthem into fibers. They have little to no tertiary structure and they are insoluble in water and are very tough - suitable for structural functions. They have hydrogen bonds which make it very flexible

Examples of fibrous proteins

Keratin, elastin, collagen

Collagen

A fibrous protein made up of three polypeptide chains which give strength to tendons, ligament, bones and skin. Each polypeptide chain is twisted to form a helix. The three polypeptide helices wind around each other like a rope with three stands using hydrogen bonds

Globular proteins

complex tertiary and sometimes quaternary structures that fold into globular shapes. the chains are usually folded so that hydrophobic groups are on the inside while hydrophilic groups are on the outside. this makes many globular proteins soluble in water

Conjugated proteins

proteins joined with another molecule called a prosthetic group which affects the performance and functions of the molecule

haemoglobin

a globular protein with four polypeptide chains and each polypeptide surrounds an iron containing haem group. the iron enables haemoglobin to bind and release oxygen molecules, and the arrangement of the polypeptide chains determine how easily oxygen binds or is released

Glycoprotein

a conjugated protein with a carbohydrate prosthetic group. the carbohydrate part of the molecule helps to hold a lot of water and makes it harder for proteases to break them down. Eg: mucus, synovial fluid

Lipoprotein

a conjugated protein important in the transport of cholesterol in blood. HDL and LDL are the two main forms of lipoprotein, and HDL contains more protein than LDL

Similarities between fibrous and globular proteins

Both chains of amino acids are joined by peptide bonds
Both contain hydrogen bonds, ionic bonds and disulfide bridges which maintains the 3D shape of the protein

Differences between fibrous and globular proteins

Fibrous proteins have hydrophobic groups on the outside while globular proteins have hydrophilic groups on the inside
Fibrous proteins have little to no tertiary structure while globular proteins have tertiary or quaternary structures
Fibrous proteins have long chains while globular proteins are folded into compact shapes