Peptides are short polymers of amino acids linked by peptide bonds. They have the same peptide bonds as those in proteins, but are usually shorter in length. We call the shortest peptides dipeptides. They consist of two amino acids joined by a single peptide bond. There can also be, tetrapipteds, pentapeptides, etc.
Peptides have an amino end and a carboxyl end, unless they are cyclic peptides. A polypeptide is a single linear chain of amino acids bonded together by peptide bonds. Protein molecules consist of one or more polypeptides put together typically in a biologically functional way and sometimes have non-peptide groups attached. They call these non-peptide groups prosthetic groups or cofactors.
Peptides, by definition must maintain certain characteristics. One of those being that you have to make peptide chains short enough. Then you can use them, to synthetically make constituent amino acids. You can then consider calling them peptides rather than proteins. However, with the advent of better synthetic techniques, peptides as long as hundreds of amino acids can be made, including full proteins like ubiquitin. Native chemical ligation has given access to even longer proteins.
Another definition places an informal dividing line at approximately 50 amino acids in length (some people claim shorter lengths). This definition is somewhat arbitrary. Long peptides, such as the amyloid beta peptide linked to Alzheimer’s disease, can be considered proteins. They consider peptides small proteins, such as insulin.
In simple terms and in a way all athletes would understand – Synthetic Growth Hormone is a complete protein and 191 amino acid chain where as CJC1295 has a 30 amino acid peptide chain.
Peptides are very new. We regard them modern, preventive, or wellness medicine. Their deign does everything from generating cells, increase REM sleep, increase sex drive, bring body fat down and increase appetite. All of the functions of peptides are beneficial to wellness, increase performance and anti ageing.