Biochemists study the chemistry of
life. Living things exhibit a large varitey of activities: eating;
sleeping; moving; talking; thinking . The unique chemical reactions
behind these activities are due to biomolecules which contain
specific functional groups.
A functional group is a group of atoms within a
molecule, which makes it react in a certain way - gives it its
chemical character. Biological molecules often have more than one
Carbohydrates all contain the
Some also contain an aldehyde group:
Carbohydrates can be divided into three classes:
- Monosaccharides, e.g. Glucose - simple
- Disaccharides, e.g. Sucrose - two
simple sugar molecules joined together
- Polysaccharides, e.g. Starch and
Cellulose - large macro molecules made up of many simple sugar
Glucose is used by the body when energy is needed,
and is converted to carbon dioxide and water inside living cells.
Any excess glucose is converted by enzymes into a polysaccharide,
glycogen, which is stored in the body.
Sucrose, a disaccharide, is converted to a
monosaccharide before it can be utilised by the body and absorbed
through the intestinal wall.
Starch is a polysaccharide formed through the
condensation polymerisation of a glucose monomer. It is broken down
by the enzyme amylase into glucose for use by the body. Starch is
the main constituent of flour, found in cereals and some vegetable
foods (rice is 75% starch, corn is 50% starch, potatoes are 20%
Martin, D. & Sampugna, J. Molecules in Living Systems (New York: Harper &