STORAGE OF FOOD AND INFORMATION

The first carbohydrate to be recognized (but not, as we have seen, by everyone) as a giant molecule was starch, or rather a water-soluble component of starch. Starch is the insoluble carbohydrate store of most plants, which, when we eat and digest it, 

There are many other polysaccharides, of which the most widely distributed is the material of plant cell walls—of wood and of cotton. This too is made up of glucose units  

Proteoglycans are found in the net (extracellular matrix) to which cells adhere, and especially in connective tissue, where they form 

Watson told the story of the discovery in his outrageously candid and captivating book. The Double Helix. With the self-confidence and ambition of his twenty-three years, he had formulated the modest plan to uncover the basis of heredity. He was in no doubt by then that DNA was indeed the genetic material, and at a meeting in Naples he had been transfixed by an X-ray diffraction picture of DNA fibres, which Maurice Wilkins had shown. It revealed the semi-crystalline nature of the DNA, and convinced him that the structure of DNA—of the gene, no less—could be cracked. Like many others of his generation, he 

The DNA chain, it was known, consists of aromatic bases, of which there are four kinds. A, G (both purines, as on p. 17), C and T (both pyrimidines), attached to a backbone, comprising units of a sugar, a pentose called deoxyiibose, and phosphate groups. The combination of base and sugar is called a nucleoside, while the base with a sugar phosphate is a nucleotide. If we represent the base (A, G, C, or T) by B, we can write the formulae as  

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