And a very, very small amount, less than 1%, actually exists in this deglucose open chain form. Now, as I mentioned, just a moment ago, we have the fissure projections that are basically used to describe the stereo chemistry, the arrangement and the three dimensional position of atoms for the open chain forms. On the other hand, we have the Holworth projections, which are used to describe the stereo chemistry of the cyclic sugars. And these are examples of the Holworth projections. Now let's take a look at another type of sugar molecules. So, remember, we have aldo hexosis, and we also have sugar molecules that contain ketone groups, and these are known as ketosis.