1.2 Carbohydrates

• Carbohydrates can be monosaccharides, disaccharides or polysaccharides.
• Monosaccharides are chemically the same but structurally different. The difference is that the carboxyl groups are switched.
• This is the alpha glucose.

  
• This is the beta glucose.

  
• Disaccharides are formed by the condensation of two monosaccharides
• Disaccharides:

  (M) Maltose = glucose + glucose

  (S) Sucrose = glucose + fructose

  (L) Lactose = glucose + galactose
• 3 examples of polysaccharides are: starches, fibers and glycogen.

  
• When monosaccharides join, a molecule of water is removed and the reaction is therefore called a condensation reaction. The bond formed is called a glucoside bond.
• The addition of water to a disaccharide that causes breakdown is called hydrolysis.
• All monosaccharides and some disaccharides (eg. Maltose) are reducing sugars.

  Reduction is a chemical reaction involving gain of electrons or hydrogen.

  Reducing sugars donate electrons to another chemical (ie. Reducing them - Reduction Is Gain).

  Testing for a reducing sugar is known as the Benedicts Test.
• In the benedict's test for reducing sugars, if a reducing sugar is present it will turn orange brown in colour.
• Polysaccharides are created by condensation reactions between many glucose monomers. Examples are (S) starch, (C) cellulose and (G) glycogen.
• Polysaccharides:

  Starch is found in plants and is a store of glucose.

  Cellulose is found in plants and is used for structural strength.

  Glycogen is found in animals and is a store of glucose.