Carbohydrates: Revision Summary B io F actsheet January 1999 Number 39 1 Carbohydrates contain 3 elements: Carbon (C), Hydrogen (H) and Oxygen (O). Thus, if we remove water from carbohydrates, all that remains is carbon. Carbohydrates can be divided into 3 categories; monosaccharides, disaccharides and polysaccharides (Table 1). Monosaccharides and Disaccharides Monosaccharides and disaccharides are sugars. They all have the basic formula (CH2O)n and can be classified according to how many carbon atoms they contain. 3C = triose sugars e.g. glyceraldehyde C3H5O2 5C = pentose sugars e.g. ribose C5H10O5 6C = hexose sugars e.g. glucose C6H12O6 Formation of disaccharides - typical exam questions Common exam questions include: