（单词翻译:单击）
Polymers-large molecules2 made up of many joined units of a more simple molecule1. Examples are polysaccharides and polypeptides.
Polypeptides; -chains of amino acids joined by peptide bonds. They are not the size of proteins, but may be biologically very active. Some hormones3 are peptides, such as insulin which has 51 amino-acid residues4. Peptides may also be powerful neurotransmitter substances.
Polyphyodont - continuous replacement5 of teeth with many generations (from "poly" =many; "phylo" = generation and "dont" =teeth). See also diphyodont
Polysaccharides - long molecules made of chains of sugars linked together. Examples are starch6, glycogen and dextrans.
Predentine - the extracellular matrix produced by odontoblasts, which becomes mineralised to form dentine. Similar in structure to osteoid.
Procaryote - a cell in which the genetic7 material is dispersed8 throughout the cell in distinction to a eucaryote which has a nucleus9 and other organelles. Bacteria and blue-green algae10 are procaryotes
Prognathic- a prominent lower jaw11 which may bring the lower teeth ahead of the upper teeth
Proline- one of 20 amino acids common in proteins. It is a common amino acid of collagen and like lycine must be hydroxylated by ascorbic acid in order to allow the formation of hydrogen bonds which will hold the triple helix together.
Proline-rich proteins - a group of proteins in saliva12 which have the ability to bind13 to calcium14. They provide the protective layer of pellicle on the tooth surfaces by binding15 to the calcium in enamel16. They also bind onto microorganism, providing a link between organism and the tooth surface. Proline rich proteins help to de-toxify tanins, which are potentially poisonous plant substances found in tea, and unripe17 fruit.
