Unit 2 Section 1.3 Carbohydrates

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  • Carbohydrates
    • what are carbohydrates made from?
      • most carbohydrates are polymers, the monomers of carbohydrates are monosaccharides. single monosaccharides are also carbohydrates though
    • Polysaccharide formation
      • monosaccharides are joined together by glycosidid bonds
      • during synthesis a hydrogen atom on one monosaccharide bonds to a hydroxyl group on the other, releasing a molecules of water - this is a condensation reaction
      • just like with the polypeptides the reverse of this reaction is hydrolysis
      • a molecule of water reacts with the glycosidic bond breaking it apart
      • a disaccharide is formed when two monosaccharides join together and a polysaccharide is formed when more than two monosaccharides join together
    • Functions of carbohydrates
      • there is a relationship between the structure and function of three polysaccharides - starch, glycogen and cellulose
        • Starch
          • starch is the main energy storage material in plants.
            • starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin
              • Amylose
                • is a long unbranched chain of alpha glucose. the angles of the glycosidic bonds are different between two alpha glucose molecules than they are between two beta glycose molecules
                  • this gives amylose a coiled structure almost like a cylinder. this makes it compact so it is really good for storage
              • Amylopectin
                • is a long branched chain of alpha glucose. its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily, this means that glucose can be released quickly
        • Glycogen
          • is the main energy storage material in animals
            • animal cells get energy from glucose too, but animals store excess glucose as glycogen
              • its structure is very similar to amylopectin except it has loads more side branches coming off it
                • loads of branches means that stored glucose can be released quickly, which is important for energy release in animals. its also a very compact molecule, so its good for storage
        • Cellylose
          • is the major component of cell walls in plants
            • its made of long unbranched chains of beta glucose
              • the bonds between sugars are straight, so the cellulose chains are straight
                • the cellulose chains are linked together by hydrogen boonds to form strong fivres called microfibrils - the strong fibres mean cellulose provides structural support for cells


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