Carbohydrates

• Carbohydrates are made of hydrogen, carbon and oxygen atoms.
• Monosaccharides are simple sugars containing three to seven carbon atoms.
• Examples of monosaccharides include glucose, galactose, and fructose.
• Galactose is found in milk.
• Fructose is found in fruit.
• Glucose is a hexose sugar with formula C6H12O6.
• Glucose is an important source of energy in humans.
• Alpha- and beta- glucose are isomers.
• Isomers have the same molecular formula but a different arrangement of atoms.
• The OH (hydroxyl) group are in a different orientation around C1.
• Two monosaccharides joining via condensation reaction form a disaccharide.
• Two disaccharides joining together form a polysaccharide chain.
• Glucose + glucose -> maltose.
• Glucose + fructose -> sucrose.
• Glucose + galactose -> lactose.
• Sucrose is common table sugar.
• Lactose is the sugar found in milk.
• Polysaccharides are made up of three or more monosaccharides joined together by glycosidic bonds.
• Chain may be branched or unbranched.
• Examples of polysaccharides include starch, glycogen, cellulose, and chitin.
• Benedict’s solution can be used to test for reducing and non-reducing sugars.
• All monosaccharides are reducing sugars.
• Some disaccharides are reducing sugars.
• Benedict’s solution is a blue liquid that changes colour when it is reduced.
• In a boiling tube, add 2ml of substance and 10 drops of Benedict’s solution.
• Place in a boiling water bath for 3-5 minutes.
• Stays blue - no reducing sugars.
• Green/yellow - small trace.
• Orange/red - moderate amount.
• Brick red - large amount.
• Non-reducing sugars will show a negative result and need a second test.
• Sucrose is a non-reducing sugar.
• Starch is a polysaccharide and a form of long term storage.
• Starch is the main energy storage material in plants.
• Starch is a large molecule so can’t leave the cell.
• Starch is stored in the seeds of plants.
• Starch is broken down into glucose when the plant needs energy.