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Types of sugar in carbohydrates

Reviewed by Dr. Amber Hayden, DO

Monosaccharides — single unit of sugar (“simple” sugars); highly soluble
Glucose The sugar circulating in our blood.
Fructose The sugar that makes fruit sweet.
Galactose The sugar found in milk.
Critical subcomponents of DNA and RNA, essential for genetic transcription.

Disaccharides — two monosaccharides joined together; soluble
(glucose + fructose + H20)
Table sugar.
(glucose + galactose + H20)
Another milk sugar.
(glucose + glucose)
Malt sugar.

Polysaccharides — long, chain-like polymers; not readily soluble
Starch (amylose and amylopectin) The energy storage molecule used by all plants, synthesized from glucose, present in all plant seeds and tubers, and in many fruits and rhizomes. The most consumed polysaccharide in the human diet.
Cellulose In plants, this is synthesized to form cell walls; it is indigestible for humans due to lack of the enzyme cellulase, but provides fiber in our diets to promote wave-like digestive action called peristalsis.
Glycogen This is the carbohydrate stored in muscle and liver tissue. When blood sugar levels go down, liver cells hydrolyze glycogen to release glucose into the bloodstream.

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1 [No author listed.] 200_. The human brain. URL: (accessed 11.19.2008). 2 Barclay, A., et al. 2008. Glycemic index, glycemic load, and chronic disease risk — a meta-analysis of observational studies. Am. J. Clin. Nutr., 87 (3), 627–637. URL (abstract): (accessed 09.26.2008). See also: Mendosa, D. 2008. Glycemic index and glycemic load. URL: (accessed 11.13.2008). Mendosa, D. 2003. Glycemic values of common American foods. URL: (accessed 11.13.2008). 3 Liang, B. 2003. Biomolecules — the carbohydrates. URL: (accessed 10.01.2008).  
Last Updated: January 19, 2022
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