Chemistry Notes for class 12 Chapter 14
Biomolecules
Biomolecules are the organic compounds which form the basis of life, i.e., they build up the
living system and responsible for their growth and maintenance.
The sequence that relates biomolecules to living organism is
Biomolecules → Organelles → Cells → Tissues → Organs → Living organism.
Carbohydrates
Optically active polyhydroxy aldehydes (aldcses) or ketones (ketoses) or compounds which on
hydrolysis give these units are known as carbohydrates. They are also called saccharides
(Latin Saccharum = sugar) due to sweet taste of simpler members.
Depending upon their behaviour towards hydrolysis, carbohydrates can be of following three
types
Monosaccharides
These cannot be hydrolysed to simpler molecules and further subdivided into tetroses, pentoses
or hexoses depending upon the number of carbon atoms. These are also called
homopolysaccharides.
Aldotetroses Erythrose, Threose
Aldopentoses Xylose, Ribose,
Aldohexoses Glucose, Galactose,
Ketohexoses Fructose
All naturally occurring monosaccharides belong to D-series.
killiani synthesis is used to convert an aldose into next higher aldose.
Oligosaccharides
(Greek oligos = few). On hydrolysis, they generally give two to nine monosaccharides (same or
different) and are further classified as disaccharides, e.g., sucrose, maltose, lactose,
trisaccharides and so on. C12H22O11 is a disaccharide because it gives two monosaccharides.
