Understanding the differences between sucrose, fructose, glucose, lactose and maltose
Sugars, or carbohydrates, are imperative for life. Sucrose, fructose, glucose, lactose, maltose and other types of sugars provide us energy; help to structure our DNA/RNA – and fulfil several other bodily functions and needs. All carbohydrates lose water and leave carbon behind when heated – hence the name “carbo” “hydrate”.
But why all of these different names and what are the differences between these various types of carbohydrates?
The different types of carbohydrates (sugars):
Monosaccharides are known as simple sugars. This simply means that a carbohydrate that is labeled as a monosaccharide cannot be broken down further. Monosaccharides are carbohydrates that are already broken down as far as they can be.
Glucose, also known as dextrose, is a 6-carbon atom sugar that is present in all living organisms. Human blood generally is found to have about 0.8g of glucose per liter. It is the primary type of carbohydrate that cells utilize in order to function. Glucose is derived from the foods that we eat and taken up into the small intestine. From there it is transported to the liver to be regulated for release into the blood. If the liver detects that too much glucose is present in the blood, it will form glycogen. If the liver detects too little glucose is present in the bloodstream, then this glycogen is again broken down into glucose. This forward and reverse process is known as glycogen metabolism.
It is another simple sugar – a monosaccharide. It lacks the sweetness of glucose, yet is also a 6-carbon atom sugar molecule. It is not as easily absorbed into the small intestine.
Disaccharides are simply sugars that are comprised of two monosaccharide units. Individual monosaccharide molecules are bound together by acetal bonds. These bound-together carbohydrates occur naturally throughout nature and form various components of our food. Additionally, they can join together with other monosaccharides and/or other disaccharides to form polysaccharides. “Poly” means “many”. Therefore polysaccharides are carbohydrates comprised of several different less complex sugar molecules. The most common and important disaccharides are saccharose, maltose and lactose.
Saccarose is also called sucrose which is just a fancy name for table sugar. It is comprised of glucose and fructose. During the process of digestion, sucrose is broken down by invertase – an enzyme produced in the small intestine. Invertase is also commonly known as sucrase.
It is also known as malt sugar, is a disaccharide comprised of two glucose molecules. Another special enzyme, maltase is used to break these glucose molecules apart and again form separate monosaccharides. Maltase is also manufactured in the small intestines.
Lactose is also called milk sugar. Of course, this is because it is present in milk. Lactose is a disaccharide that is comprised of one molecule each of galactose and glucose. Again, a special enzyme called lactase, produced in the small intestine, acts to break down lactose into its individual monosaccharide units. Many people lack the ability to manufacture lactase and are therefore considered lactose intolerant.
Lactose intolerance is characterized by the following symptoms:
- General pain;
It’s interesting to note that 3% of Danish people are lactose intolerant and that 97% of Thai people are.