Draw an aldohexose. Draw the molecule on the canvas by choosing buttons from the Tools (for bonds and charges), Atoms, and Advanced Template toolbars. Tip: The single bond is active by default.
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Part B
Draw a ketohexose. Draw the molecule on the
The Correct Answer and Explanation is:
To fulfill your request, I’ll describe how to draw both an aldohexose and a ketohexose and then provide a 300-word explanation to clarify the concepts.
Aldohexose: Drawing Instructions
- Start with a six-carbon backbone (hexose):
- Draw a straight chain of six carbon atoms using single bonds.
- **Add an *aldehyde* group to carbon 1:**
- On the first carbon, draw a double bond to an oxygen atom (=O), indicating the aldehyde functional group.
- Add hydroxyl (-OH) groups:
- Attach one hydroxyl group (-OH) to each of the remaining carbons (C2–C5).
- Carbon 6 will have a CH2OH group.
- Fill in remaining bonds with hydrogen atoms to ensure carbon has four bonds.
An example of an aldohexose is D-glucose in its Fischer projection form.
Ketohexose: Drawing Instructions
- Start with a six-carbon backbone (hexose):
- Draw a straight chain of six carbon atoms.
- **Add a *ketone* group to carbon 2:**
- On the second carbon, add a double bond to an oxygen atom (=O), indicating the ketone functional group.
- Add hydroxyl (-OH) groups:
- Attach -OH groups to carbons 3–5.
- Carbon 1 and carbon 6 will each have a CH2OH group.
An example of a ketohexose is D-fructose.
300-Word Explanation
A hexose is a monosaccharide (simple sugar) with six carbon atoms. There are two main types of hexoses: aldohexoses and ketohexoses, and they differ based on the functional group they contain.
An aldohexose has an aldehyde group (-CHO) on carbon 1. The rest of the carbon atoms typically bear hydroxyl groups (-OH), except the last carbon, which ends in a CH2OH group. The most well-known example is glucose. Aldohexoses typically appear in linear form in dry environments but often cyclize in aqueous solutions, forming ring structures like pyranoses.
In contrast, a ketohexose has a ketone group (C=O) on carbon 2 instead of an aldehyde group. This shifts the position of the carbonyl group, and the molecule retains hydroxyl groups on the remaining carbons, with terminal CH2OH groups on both ends. Fructose is the most common ketohexose. Like glucose, it can cyclize in solution, but it tends to form furanose (5-membered) rings instead of 6-membered rings.
The position of the carbonyl group determines both the classification and the reactivity of the sugar. Aldehydes are more readily oxidized than ketones, which is important in biochemical tests like Benedict’s or Fehling’s test that detect reducing sugars.
Understanding these structures is essential in biochemistry and nutrition, as glucose and fructose are key energy sources in metabolic pathways like glycolysis. The presence of different functional groups and spatial arrangements also defines their interaction with enzymes and their behavior in various biological systems.
Let me know if you’d like the images of both structures drawn as well!