Biology - Carbohydrates

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Carbohydrates      contain         3          elements      these      are:

  • Carbon
  • Hydrodgen          and
  • oxygen

Carbohydrates       are      found      in       three       forms       these      are:

  • Monosaccharides
  • Disaccharides          which       are     double       sugars    and
  • polysaccharides


General              formula              is:

(CH2O)n           where           n          is           a              number                between          3                and              9.                They                 are                      classified                     according              to             the            number                 of                 carbon                   atoms.             The monosaccharides                  you              will                  have             to              know             fall              into               these                       categories:

C = 3 = triose

C = 4 = tetrose

C = 5 = pentose

C = 6 = hexose

Trioses:                          (e.g.                  glyceraldehydes),                intermediates                   in                               respiration                 and                    photosynthesis.

Tetroses:                    rare.

Pentoses:                       (e.g.                  ribose,                      ribulose),               used                    in                           the                                      synthesis                  of                            nucleic                           acids              (RNA                    and                     DNA),                  co-enzymes             (NAD, NADP,                              FAD)                    and                            ATP.

Hexoses:                        (e.g.                     glucose,                       fructose), used                       as                    a                      source               of               energy                  in                   respiration                       and                as                  building                                         blocks               for          larger                   molecules.

All                  but                   one                   carbon                           atom                      have                    an                           alcohol                 (OH)                   group                           attached.                      The                 remaining                     carbon                                  atom                     has                 an                            aldehyde                    or                ketone              group                               attached.

Ring form:


Due                    to                         the                      bond                       angles           between                the             carbon                       atoms,            it               is                   possible                       for                  pentoses             and                 hexoses                  to                             form                     stable                 ring                    structures.                           The            carbon         atoms            are                          numbered               1             to          5                    in                        pentoses                  and               1              to                      6                  in                          hexoses.

Depending                          on                         the                    orientation                 of                     the                      OH                   group               on             carbon             1,                   the                     monosaccharide              can             have                    either             α             or                 β                         configurations.

Disaccharides and glycosidic bonds

These                            are                             formed                             when                two                            monosaccharides                    are                 condensed                          together.                   One                       monosaccharide                                      loses                an                  H                 atom                       from                     carbon                     atom                number       1                and                 the                  other                 loses           an                 OH                          group                     from               carbon          4              to               form                        the                     bond.

The                  reaction,                             which                              is                  called                                     a                                 condensation                        reaction,                  involves                     the                       loss                  of            water           (H2O)                  and                  the                       formation                 of                     an                          1,4-glycosidic bond.                  Depending                             on                           the                monosaccharides                      used,                     this                      can                  be                   an                      …




The information is helpful but the layout is appaling

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