Now, generally speaking, there are two types of categories of sugars. We have those sugars that contain aldehyde groups, and these are known as aldosis. And we have those sugars that contain a ketone group, and these are known as ketosis. And to demonstrate what the difference is, let's take a look at the simplest monosaccharide that contains and value that is equal to three. So this is the ketos that consists of three carbons, six H atoms and three oxygens. And notice it's a ketos because on both sides of this carbon ill group, we essentially have these carbon atoms.