Carbohyderates

• Carbohydrates

  Molecules which consist only of carbon, hydrogen, and oxygen

  They are long chains of sugar units called saccharides
• What is a single monomer called?

  monosaccharide
• What is a pair of monomers called?

  Disaccharide
• What forms when combining many monosaccharides?

  Polysaccharides (poly=many)
• How are carbohydrates joined together?


  Joined together with a glycosidic bond

  Formed in a condensation reaction

  Hydrolysis is the reverse reaction
• Monosaccharides

  Monomers from which larger carbohydrates are made
• Common monosaccharides

  glucose, fructose, galactose

  - sweet tasting and soluble substances

  - general formula (CH2O)n
• Glucose

  - a monosaccharide containing six carbon atoms in each molecule

  - main substrate for respiration

  - has two isomers: alpha and beta glucose
• Disaccharides

  When two monosaccharides join together in a condensation reaction (a molecule of water is produced)
• maltose

  Disaccharide formed by condensation reaction of two glucose molecules
• Sucrose

  Disaccharide formed by condensation of glucose and fructose
• Lactose


  Disaccharide formed by condensation of glucose and galactose
• Glycogen and starch is formed by

  The condensation of alpha glucose
• Starch


  Stores energy in plants and is a mixture of two polysaccharides called amylose and amylopectin
• Cellulose is formed by


  Condensation of β-glucose
• Amylose


  - unbranded chain of glucose molecules joined by 1, 4 glycosidic bonds, and as a result is coiled and thus a very compact molecule that stores lots of energy
• Amylopectin


  - branched and is made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds

  - due to the presence of many side branches these can be acted upon simultaneously by many enzymes and thus broken down to release energy
• test for starch


  Iodine solution

  -Posotive:Blue black

  -Negative:Orange brown
• structure related to its function: Cellulose

  Every other beta-glucose molecule is

  inverted in a long, straight,

  unbranched chain

  Many hydrogen bonds link parallel

  strands (crosslinks) to form micro

  fibrils (strong fibres)

  H bonds are strong in high numbers

  Provides strength and structural

  support to plant cell walls
• cellulose function

  provides strength and structural support to plant cell walls
• structure related to its function: starch

  Helical; compact for storage in cell

  Large polysaccharide molecule; can’t leave cell

  Insoluble in water; water potential of cell not affected i.e. no osmotic effect
• Glyocgen function

  energy store in animal cells
• structure related to its function: glycogen

  Branched; can be rapidly hydrolysed to release glucose for respiration to provide energy

  Large polysaccharide molecule; can’t leave cell

  Insoluble in water; water potential of cell not affected i.e. no osmotic effect