The aldose molecules have five hydroxyl groups. The majority of aldose molecules usually has a cyclic structure. Often, when the molecules of a hydrocarbon have a cyclic structure, they would form a six-member ring structure, which is called a hemiacetal ring because of the presence of carbon. Ketose, on the other hand, is a sugar which has one ketone group for each of its molecule.
Some examples of Ketose include pentoses, hexoses, across, trioses, tetroses, heptoses, etc. Hexoses can also be referred to as ketoses if their group includes sorbose, fructose, psicose, and tagatose. Some of the rich sources of fructose include fruits such as agave.
Some other sources of fructose include dates, raisins, prunes, figs, etc. Even honey and molasses do contain a high dose of fructose. Some processed foods such as ketchup, barbecue sauce, salad dressings, and cereals, sweet-and-sour sauces, etc. are also a high source of fructose.