Structure and stereochem of sugars
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Epimers: Isomers that differ only in configuaration of a single carbon.
Details about cyclic isoforms of monosaccharides:
- All monosaccharides with >5 carbons are cyclic in aqueous solution.
- Carbonyl carbon forms hemiacetal/hemiketal with internal hydroxyl group (intramolecular reaction between aldehyde/ketone and alchohol).
Mutarotation of Glucose: how it comes to be and what results.
- D-glucose forms an intramolecular hemiacetal between hydroxyl at C-5 and aldehyde at C-1.
- Results in 2 cyclic anomers (special case of epimers): alpha/beta-D-glucopyranose.
- A 6-membered ring.
- Aldohexoses form 6-membered rings.
- A 5-member ring.
- Ketohexoses and aldopentoses form 5-member rings.
What are derivatives of monosaccharides?
- It is when hydroxyl groups of monosaccharides are replaced with other groups such as amino groups.
- It can happen when oxidation of C1 carbonyl group occurs --> aldonic acid.
- It can happen when oxidation of carbon farthest from carbonyl group , C6, occurs --> uronic acid.
Define glycosidic bond:
What can this bond do?
- Glycosidic bond: Anomeric carbon of one sugar reacts with hydroxyl group of another sugar.
- The glycosidic bonding converts hemiacetal/hemiketal into acetal/ketal and produces H2O.
- The process of glycosidic bonding is slow, these bonds don't break easily.
- Anomers: differ only in the configuration of the hemiacetal or hemiaketal carbon.
- Anomers are found on the reducing end of cyclic glucose, anomeric carbon.
Monosaccharides joined by O-glucosidic bonds by process of condensation, H2O is a product in creating disccharaides.
What are biologically important disaccharides?
- Disaccharides that are non-reducing.
- Bond is formed between two anomeric carbons. Double-headed arrow connects anomeric carbons. (beta2 <-> 1alpha).
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