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POLYSACCHARIDES

POLYSACCHARIDES. From Greek: Poly meaning many Sacchar meaning sugar Are made from sugars. Carbohydrates/sugars:. Are the fuel and building blocks for life Are building blocks (monomers) for polysaccharides Examples monosaccharides: Glucose Fructose. Synthesis.

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POLYSACCHARIDES

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  1. POLYSACCHARIDES From Greek: Poly meaning many Sacchar meaning sugar Are made from sugars

  2. Carbohydrates/sugars: • Are the fuel and building blocks for life • Are building blocks (monomers) for polysaccharides • Examples monosaccharides: • Glucose • Fructose

  3. Synthesis • Linking monosaccharides (sugars) together • The most common monosaccharide, glucose – C6H12O6, is of central importance in the chemistry of life • Dehydration synthesis process:

  4. Key Characteristics of Sugars • They are hydrocarbons with carbonyl groups (C=O) and multiple hydroxyl groups (OH) • Carbon skeletons are 3 to 7 carbons long. • Their names end in the suffix “ose”.

  5. Ketose vs Aldose • If the carbonyl group is in the middle of the chain it is classified as a ketose, and if it is on the end of a chain as an aldose.

  6. Small differences in structure can cause major differences in the behaviour and shape of the sugar

  7. Galactose and glucose are optical isomers (same number and types of atoms, different properties). • Galactose is not very water-soluble therefore is not easily absorbed – is not digested

  8. When in water (aqueous solution) most sugars form rings. • Example: Glucose • Chemical equilibrium between the linear and ring structure favors the ring structure.

  9. Naming sugars: • Prefixes of: Mono, di, tri, … poly • Mono is a single sugar • Di = two sugars joined • Tri = three sugars joined • Poly = many sugars joined

  10. Depending on the size of a carbon skeleton (ranges from 3 – 7), monosaccharides are named as: • Trios – 3 carbon chain • Tetrose – 4 carbon chain • Pentose – 5 carbon chain • Hexose – 6 carbon chain • Heptose – 7 carbon chain • Aldose vs. Ketose (See earlier notes)

  11. Forming name:  (keto-/aldo-) + (# of carbons) + -ose Examples • a monosaccharide that contains an aldehyde and three carbons is formed in this way: • aldo- + tri + ose ------> aldotriose • a five carbon sugar that contains a ketone is called a ketopentose.

  12. TASK • Worksheet questions 1 - 9

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