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|Section2= |Section6= |Section7= }} Galactose (''galacto-'' + ''-ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is less sweet than glucose and fructose. It is a C-4 epimer of glucose. Galactan is a polymer of the sugar galactose found in hemicellulose. Galactan can be converted to galactose by hydrolysis. ==Structure and isomerism== Galactose exists in both open-chain and cyclic form. The open-chain form has a carbonyl at the end of the chain. Four isomers are cyclic, two of them with a pyranose (six-membered) ring, two with a furanose (five-membered) ring. Galactofuranose occurs in bacteria, fungi and protozoa. 〔Nassau et al. (Galactofuranose Biosynthesis in Escherichia coli K-12:... ) JOURNAL OF BACTERIOLOGY, Feb. 1996, p. 1047–1052〕 In the cyclic form there are two anomers, named alpha and beta, since the transition from the open-chain form to the cyclic form involves the creation of a new stereocenter at the site of the open-chain carbonyl. In the beta form, the alcohol group is in the equatorial position, whereas in the alpha form, the alcohol group is in the axial position.〔(Ophardt, C. Galactose )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「galactose」の詳細全文を読む スポンサード リンク
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