Carbohydrates

• Monosaccharides


  These are the monomers from which larger carbohydrates are made. Common examples include glucose, fructose and galactose.
• Bonding

  A condensation reaction between two monosaccharides forms a glycosidic bond. The condensation reaction means the product loses a water molecule.
• Molecular formula.


  Triose monosaccharides have the general formula C3H6O3

  Pentose monosaccharides have the general formula C5H10O5

  Hexose monosaccharides have the general formula C6H12O6
• Disaccharides


  These are formed by the condensation of two monosaccharides.

  Maltose is alpha glucose and alpha glucose (this produces a 1,4 glycosidic bond).

  Sucrose is alpha glucose and fructose.

  Lactose is alpha glucose and galactose.
• Uses of disaccharides.


  Maltose is used in brewing.

  Sucrose is used in sweeteners.

  Lactose is milk sugar.
• Glucose


  Glucose has two isomers, alpha and beta.

  An isomer has the same molecular formula but a different structural formula.

  Alpha glucose has the hydroxyl group bonded below the hydrogen atom at carbon 1, whereas beta has this group bonded above the hydrogen atom at carbon 1.
• Carbohydrates


  All carbohydrates are made from carbon, oxygen and hydrogen atoms.
• Starch


  Starch is made from the condensation of alpha glucose. It is a polysaccharide.

  Starch has 2 components - amylose and amylopectin.

  Amylose contains only 1,4 glycosidic bonds. It is coiled and unbranched.

  Amylopectin contains 1,4 and 1,6 glycosidic bonds. This means it is uncoiled and branched.

  So, starch as a whole is branched and coiled.
• Glycogen.


  This is very similar to starch structurally.

  However, it has more 1,6 glycosidic bonds.

  This means it has more branches and so more receiving ends.

  This is important because glycogen is found in animals, which need more energy than plants - more receiving ends means more glucose which is readily available to be hydrolysed for use in respiration.
• What are the structures and functions of glycogen and starch?


  Coiled - compact for storage.

  Insoluble molecule - osmotically inactive.

  Branched - glucose is easily hydrolysed.

  Large molecule - does not cross cell membrane.
• What are 4 structural features of glycogen and starch?


  Coiled

  Branched

  Insoluble

  Large
• Give 3 monosaccharides


  Glucose

  Galactose

  Fructose
• What type of bond is produced in the condensation of 2 monosaccharides?

  Glycosidic bond
• What are the 2 components of starch?

  Amylose and amylopectin
• Cellulose


  Made from the condensation of beta glucose.

  Only contains 1,4 glycosidic bonds and is straight chained due to alternating beta glucose molecules being rotated 180 degrees.

  Each cellulose chain forms hydrogen bonds with it neighbours, which produce bundles called microfibrils and these in turn form larger bundles called fibrils.
• What are the smaller bundles of cellulose chains called?


  Microfibrils
• Cellulose structure and function


  Long, straight, unbranched chains of beta glucose - long microfibrils are formed.

  Hydrogen bonding between chains - provides rigidity and strength.
• What are 4 structural features of cellulose?


  Insoluble

  Large

  Long, straight, unbranched chains (long microfibrils)

  Hydrogen bonding between chains (strength and rigidity)
• What are 4 differences between starch and cellulose?

  Starch is:

  Polymer of alpha glucose (cellulose is beta)

  Coiled (cellulose is straight chained)

  Branched/also contains 1,6 glycosidic bonds (cellulose only contains 1,4)

  No microfibrils (cellulose has microfibrils)