Carbohydrates

ID #2175

What are the consequences of circularizing a sugar, specifically ketose and aldose?


The last slide from Lecture 3 illustrates how to circularize a linear hexose sugar. Specifically, on the left column, the slide shows two different monosaccharides with an aldehyde group at the C1 position (look at the linear chain). An aldehyde group is comprised chemically of H-C=O where the C is also linked to something else, which we generally abbreviated as "R". That is why this sugar is an aldose sugar because it contains an aldehyde group. 

Another chemical group is called a ketone, which is chemically comprised of "R"-C=O, where the C is also connected to something else that we abbreviate "R or R2". In ketone containing sugars, or ketose sugars, the ketone group is at position C2. If you look at the right column of the same slide mentioned above, you'll see fructose as an example of the end result of circularizing a ketose sugar. Since the C=O is located at C2, you'll see the O that is in the ring is now covalently linked to the C2 position (NOT C1), meaning that the C1 position of a ketose sugar is not in the ring (look right below the ring). 

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