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POLYSACCHARIDES

POLYSACCHARIDES. From Greek: Poly meaning many Sacchar meaning sugar Are made from sugars. Polysaccharides. Glucose monomer. Starch granules in potato tuber cells. (a) Starch. Glycogen Granules In muscle tissue. (b) Glycogen. Cellulose fibril in a plant cell wall.

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POLYSACCHARIDES

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

  2. Polysaccharides Glucose monomer Starch granules in potato tuber cells (a) Starch Glycogen Granules In muscle tissue (b) Glycogen Cellulose fibril in a plant cell wall Cellulose molecules (c) Cellulose Figure 3.13

  3. One familiar example of a polysaccharide is starch • Plant cells store starch for energy • Potatoes and grains are major sources of starch in the human diet

  4. Animals store excess sugar in the form of a polysaccharide called glycogen • Glycogen is similar in structure to starch

  5. Cellulose is the most abundant organic compound on Earth • It forms cable-like fibrils in the tough walls that enclose plants • It is a major component of wood • It is also known as dietary fiber

  6. Most animals cannot derive nutrition from fiber • How do grazing animals survive on a diet of cellulose? • They have bacteria in their digestive tracts that can break down cellulose

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

  8. 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

  9. 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”.

  10. 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.

  11. 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

  12. 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)

  13. 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.

  14. TASK • Worksheet questions 1 - 9

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