1.Complex carbohydrates are heterogenious and not easy to characterize by physical and/or chemical analysis. 2.Carbohydrates are not genetically determined.Complex structure are build by a sequential addition of monomeres using different enzymes. 3.Carbohydrates have usually passive functions within cells.Thus functional assays to measure its biological activity are difficult to develop. Nevertheless:carbohydrates are essential compounds in all cells 1.Energy metabolism and energy storage. 2.Ribose and deoxyribose as components of RNA DNA. 3.Carbohydrates are essential components of glycoproteins and glycolipids. 4.Carbohydrates are important components of zell walls of bacteria and plants.1. Complex carbohydrates are heterogenious and not easy to characterize by physical and/or chemical analysis. 2. Carbohydrates are not genetically determined. Complex structure are build by a sequential addition of monomeres using different enzymes. 3. Carbohydrates have usually passive functions within cells. Thus functional assays to measure its biological activity are difficult to develop. Nevertheless: carbohydrates are essential compounds in all cells ! 1. Energy metabolism and energy storage. 2. Ribose and deoxyribose as components of RNA / DNA. 3. Carbohydrates are essential components of glycoproteins and glycolipids. 4. Carbohydrates are important components of zell walls of bacteria and plants