Principles of Biochemistry

3.1.2.1 Monosaccharide

A monosaccharide is a carbohydate that contains a single polyhydroxy aldehyde or polyhydroxy ketone unit.  Monosachharides can not be hydrolyzed to simpler carbohydrates. They may be subdivided into trioses, tetroses, pentoses, hexoses or heptoses depending upon the number of carbon atoms they posses. Pentoses and hexoses are important simple sugars present in food.

 

Type of pentose	Source	Functions
D-Ribose	Nucleic acids	Structural elements in nucleic acids and                    coenzymes, e.g. ATP, NAD, NADP,flavoprotein. Ribose- phosphate is an inter mediates in pentose phosphate pathway.
D-Ribulose	Formed  in metabolism	Ribulose phosphate is an intermediate in pentose phosphate path way.
D-Arabinose	Gum arabic, plum and cherry gums.	Constituent of glycoproteins
D-Xylose	Wood gums, proteoglycans, glycosaminoglycans	Constituent of glycoproteins

 

 

Type of Hexose	Source	Functions
D-Glucose	Fruit juices. Hydrolysis of starch, cane sugar maltose, and lactose.	The free sugar of the body. The sugar carried        by the blood, and the principal one used by the tissues.
D-Fructose	Fruit juices, Honey,  Hydrolysis of cane sugar.	It can be changed to glucose in the liver and thus used in the body.
D-Galactose	Hydrolysis of lactose.	It can be changed to glucose in the liver and metabolized. It is synthesized in the mammary gland to make the lactose of milk. It is a constituent of glycolipid and glycoprotein.
D-Mannose	Hydrolysis of plant mannan(plant polysaccharides) and gums.	It is a constituent of many glycoproteins.