Food chemistry
Comprising 75% of the biological world and 80% of all food intake for human consumption, the most common known human carbohydrate is Sucrose. The simplest version of a carbohydrate is a monosaccharide which contains carbon, hydrogen, and oxygen in a 1:2:1 ratio under a general formula of CHO where n is a minimum of 3. Glucose is an example of a monosaccharide as is fructose. Combine them in the picture shown to the right and you have sucrose, one of the more common sugar products around.
Heparan sulfate
Heparan sulfate is a member of the glycosaminoglycan family of carbohydrates and is very closely related in structure to heparin. Both consist of a variably sulfated repeating disaccharide unit. The main disaccharide units that occur in heparan sulfate and heparin are shown below.
The most common disaccharide unit within heparan sulfate is composed of a glucuronic acid (GlcA) linked to "N"-acetylglucosamine (GlcNAc) typically making up around 50% of the total disaccharide units. Compare this to heparin where IdoA(2S)-GlcNS(6S) makes up 85% of heparins from beef lung and about 75% of those from porcine intestinal mucosa. 
Problems arise when defining hybrid GAGs that contain both 'heparin-like' and 'HS-like' structures. It has been suggested that a GAG should qualify as heparin only if its content of N-sulfate groups largely exceeds that of N-acetyl groups and the concentration of O-sulfate groups exceeds those of N-sulfate.
Not shown below are the rare disaccharides containing a 3-O-sulfated glucosamine (GlcNS(3S,6S) or a free amine group (GlcNH). Under physiological conditions the ester and amide sulfate groups are deprotonated and attract positively charged counterions to form a salt. It is in this form that HS is thought to exist at the cell surface.Many different cell types produce HS chains with many different primary structures. Therefore, there is a great deal of variability in the way HS chains are synthesised, producing structural diversity encompassed by the term "heparanome" - which defines the full range of primary structures produced by a particular cell, tissue or organism. However, essential to the formation of HS regardless of primary sequence is a range of biosynthetic enzymes. These enzymes consist of multiple glycosyltransferases, sulfotransferases and an epimerase. These same enzymes also synthesize heparin.