Glucose
Glucose is a monosaccharide (or simple sugar). Monosaccharides are the simplest type of carbohydrate and can be combined to form more complex sugars and carbohydrates. As the 3DChem website notes, glucose is also important in biology because it is one of the main products of photosynthesis. Glucose comes in two different forms which are known as stereoisomers, which differ only in the orientation of the different atoms. In nature, only one stereoisomer, known as D-glucose, can be used biologically. Glucose is one of the most common sources of biological fuel as it is used by virtually all living organisms. Glucose is metabolized using a series of chemical reactions called respiration. Glucose can be broken down in the presence of oxygen (aerobic respiration) or without oxygen (anaerobic metabolism). Aerobic metabolism generates much more energy per unit of glucose than anaerobic.
Sucrose
Sucrose is a disaccharide, which means it is made up of two monosaccharides that are chemically linked together. As the Elmhurst Virtual Chembook website explains, sucrose is made up of one molecule of glucose and one of another monosaccharide, called fructose. Sucrose is typically used as table sugar because of its sweet taste. Glucose and fructose are turned into sucrose using a condensation chemical reaction, which means that water is produced as a byproduct. The chemical bond formed between the two sugars is known as an ether bond.
Starch
According to the London South Bank University website, starch is a complex polysaccharide, when means that it is made up of many different monosaccharides. Starch is actually made up of many different glucose molecules that are chemically bonded together. Starch is an important carbohydrate, because it can store many different molecules of glucose for later use. The glucose molecules can be linked in two different ways. One type of linkage causes the glucose molecules to form a long chain and the other causes branching of the starch carbohydrate. The number of branches gives different kinds of starches different properties.
