Protein structure and functionBlack print – notes

Red print – syllabus content

Amino Acids

There are 20 different amino acids in the body eg. Phenylalanine, asparagine, glutamic acid

Amino acids are linked by peptide bonds to form polypeptide chains

Amino Acids Peptide bonds

This is polypeptide chain. The protein is not yet completed

Amino acids are linked by peptide bonds to form polypeptides.

These represent amino acids

Proteins are held in a three dimensional shape by peptide bonds, hydrogen bonds, interactions between individual amino acids. Polypeptide chains fold to form the three dimensional shape of the protein. Proteins have a large variety of structures and shapes resulting in a wide range of functions.

The amino acid sequence is the primary structure of the protein.

Hydrogen bonds form between certain amino acids twisting the polypeptide into a helix or a pleated sheet.

Peptide bonds, hydrogen bonds and other types of bonds and interactions between amino acids give the protein a three dimensional shape:

Different polypeptide chains are joined and folded to give the final shape of the protein molecule.Protein molecules may be rope shaped (fibrous proteins) or globe shaped (globular proteins)

Summary of protein structure

Fibrous protein Body tissue where protein found

Collagen Bone

Actin Muscle

Myosin Muscles

Keratin Hair, nails

Elastin Lining of Arteries

Fibrous Proteins

Table for illustration not for memorising

Globular Proteins

Globular Protein Use of globular protein

Enzymes Biological catalysts. Each folded in a way to expose an active surface to combine with a specific substrate

Hormones Chemical messengers made by an endocrine gland. Transported to target tissue in blood to exert specific effect such as a regulatory effect on growth or metabolism

Antibodies Made by white blood cells called lymphocytes and defend the body against antigens

Transport proteins Responsible for transporting substances from one part of the body to another eg transferrin binds with iron entering bloodstream from the gut or released during the destruction of red blood cells and transports it to the bone marrow for re-use

Structural proteins Forms essential part of all membranes possessed by structures within the cell such as the nucleus. So plays a vital structural role in every living cell

Table for illustration not for memorising

Conjugated Protein

Use

Glycoprotein Composed of protein and carbohydrate, eg mucus, a slimy, viscous substance secreted by epithelial cells to lubricate or protect parts of the body

Lipoprotein Complex molecule consisting of protein and lipid. Products of fat digestion absorbed from the small intestine are coated with lipoprotein before being transported around the body.

Haemoglobin The oxygen transporting pigment in the blood. Is a conjugated protein consisting of the globular protein globin associated with haem, a non-protein part containing iron.

Conjugated Proteins

A conjugated protein consists of a globular protein associated with a non-protein chemical.

Table for illustration not for memorising