Ribosomes, large complexes of protein and ribonucleic acid (RNA), are the cellular organelles responsible for protein synthesis.

The endoplasmic reticulum (ER) is a large, dynamic structure that serves many roles in the cell including calcium storage, protein synthesis and lipid metabolism.

A key determinant of the rate of protein synthesis is translation initiation, a process regulated in part through binding of initiator methionyl-tRNA (met-tRNAi) and messenger RNA (mRNA) to a 40S ribosomal subunit. Either the met-tRNAi or mRNA binding step can become limiting for protein synthesis.

Protein synthesis deficiency can be caused by mutations in any component of the translation apparatus including tRNA, rRNA and proteins. It can therefore present any mode of inheritance. Until now only maternal and autosomal recessive transmission of these deficiencies has been observed.

tertiary structure

The amino acid sequence of a protein determines its three-dimensional shape. Primary structure – the linear sequence of residues (amino acids) in a polypeptide chain.

It is convenient to describe protein structure in terms of 4 different aspects of covalent structure and folding patterns. The different levels of protein structure are known as primary, secondary, tertiary, and quaternary structure.

Important functional characteristics of proteins include their glass transition temperature, melting point, isoelectric point, molecular weight, secondary structure, solubility, surface hydrophobicity and emulsification [8].

They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs. Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains.

Although amino acids may have other formulas, those in protein invariably have the general formula RCH(NH2)COOH, where C is carbon, H is hydrogen, N is nitrogen, O is oxygen, and R is a group, varying in composition and structure, called a side chain.

Globular proteins are spherical in shape and usually water soluble. Examples of globular proteins include haemoglobin, insulin and many enzymes in the body.

Protein foods

• lean meats – beef, lamb, veal, pork, kangaroo.
• poultry – chicken, turkey, duck, emu, goose, bush birds.
• fish and seafood – fish, prawns, crab, lobster, mussels, oysters, scallops, clams.
• eggs.
• dairy products – milk, yoghurt (especially Greek yoghurt), cheese (especially cottage cheese)