Glucose

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hain with a C=O (a carbonyl group) attached to one of its ends. A carbonyl group contains a C=O bond inside the structure of a molecule, which in turn means that the carbon atom is double-bonded to the oxygen atom. If a molecules is know to have an aldehyde group, it means at either ends of the structure it has the formula of R-C=O. In the glucose molecule, R in the aldehyde group is a hydrogen atom. The prefix aldo- is placed before the root word of how many carbons the molecule contains if the molecule contains an aldehyde group. Glucose contains an aldehyde group at Carbon 1 (H-C=O), and it contains six carbons so therefore it is called an aldohexose.
Glucose has many compounds with same molecular formula, but different properties and structures, or isomers. Glucose is not the only molecule with the same molecular formula of C6H12O6. One type of isomer is a structural isomer, in which the number of atoms and the molecular formula stays the same, but the arrangement of the molecules differ. For example, a structural isomer of glucose is fructose which indeed keeps the same molecular formula as glucose, but whose structure differs. The difference between both compounds is that fructose has its carbonyl group in the inner carbon, and therefore called a ketohexose, while glucose has its carbonyl group at the end carbons calling it a aldohexose. Therefore, glucose and fructose are structural isomers of each other.
Another subclass of isomers is called stereoisomers. Stereoisomers is an isomer whose molecules have the same atoms bonded to each other and same formula, but differ in the way these atoms are arranged in space. Glucose and galactose are stereoisomers of the disasteomer subclass because they are both aldohexoses and they contain the same number of atoms in the same order from top to bottom. Although they obtain those similarities, the difference between both of them is that the second chiral carbon (C-3) in both molecu...