Carbohydrates (Trioses, Tetroses, Pentoses, and Hexoses) Carbohydrates (not to be confused with hydrocarbons) are complex compounds made by combining hydroxyl and carbonyl groups in compounds. In carbohydrates, the number of oxygen atoms equals the number of carbon atoms (3 or more) and the number of hydrogen atoms equals the sum of the number of carbon and oxygen atoms (IC:2H: 10). Even though both formaldehyde and acetic acid display this ratio of elements, they are not considered to be carbohydrates. 1. Trioses (3-carbon sugars) glyceraldehyde CH2OHCHOHCOH a. H OH C H C CO H Skip the lame foot part Build a model of this molecule. Identify the carbonyl and both hydroxyl groups (one is primary and the other is secondary). Place you model on the table so that it resembles a dog with its ears pinned back. Locate the primary hydroxyl group. This part of the molecule represents the dog's tail. Identify the secondary hydroxyl group. This forms a lame (hurt) front foot. Is the lame foot on the left or right side of the dog? Is it possible to rotate the molecule (without breaking the bonds) in order to put the lame foot on the other side of the dog? Yes. It is possible to rotate molecule without breaking the bonds. If you break a bond to switch the lame foot to the other side, what molecule have you constructed? What is the relationship of this molecule to the previous glyceraldehyde molecule