An Introduction to Carbohydrates
Monosaccharides Vary in Structure
§ Monosaccharide monomers are simple sugars that structurally vary in four primary ways: •
Location of the carbonyl group

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Aldose: found at the end of the monosaccharide

Ketose: found in the middle of the monosaccharide
Number of carbon atoms present

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Triose: three
Pentose: five Hexose: six
Spatial arrangement of their atoms

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Different arrangement of the hydroxyl groups
Linear and alternative ring forms

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Sugars tend to form ring structures in aqueous solutions

Thus each Each monosaccharide has a unique structure and function
The Structure of Polysaccharides
§ Polysaccharides, or complex carbohydrates, are polymers of monosaccharide monomers § The simplest polysaccharides are disaccharides

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Comprised of two monosaccharide monomers

The monomers can be identical or different
Simple sugars polymerize when

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A condensation reaction occurs

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Between two hydroxyl groups

Resulting in a covalent bond called a glycosidic linkage
Glycosidic Linkages
§ The glycosidic linkages can form

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Between any two hydroxyl group

The location and geometry of these bonds vary widely among polysaccharides α-1,4-glycosidic linkage and β-1,4- glycosidic linkage

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Both linkages are between the C-1 and C-4 carbons
Their geometry is different

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α and β refer to the contrasting orientations of the C-1 hydroxyls
They are on opposite sides of the plane of the glucose rings

Watch this video https://www.youtube.com/watch?v=LBwSh8Q3sgs Types of Polysaccharides
• Plants store sugar as starch

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Mixture of branched (amylopectin) and unbranched (amylose) α-glucose polymer Animals store sugar as glycogen

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Highly branched α-glucose polymer
Cellulose: a