Salivary
amylase is involved in the breakdown of carbohydrates before they
even reach our stomach. Carbohydrates are the major source of energy
for the body and include starches, sugars and fibre. Fibre is indigestible
but we need it for our digestive system to work smoothly. Sugars
are quickly and easily taken up into the bloodstream - this is why
you can eat a chocolate bar for instant energy. Starches are long
polysaccharide chains - chains of sugar monomers joined together
and take longer to digest. Starches make better foods to keep you
full up for a long time as their energy is released slowly.
To aid digestion, the body starts chopping the starches into
small sugar molecules as soon as we put then in our mouth. Amylase
acts on starch to produce maltose (a disaccharide) - this is further
broken down in the small intestine by maltase to give 2 glucose
monomers. (Notice that the names of most enzymes end in -ase,
and the first part of the name often tells us what the enzyme
is doing or what it is acting on). Other enzymes exist in the
body to break down other disaccharides, such as sucrase, which
breaks down sucrose (cane sugar) and lactase, which breaks down
lactose (milk sugar). It is a lack of lactase that leads to lactose
intolerance, a fairly common dietary disorder.
When you chew a piece of bread for a few minutes you will notice
that it begins to become sweet. This is because the amylase is
hydrolyzing the bonds between the individual sugar monomers to
give maltose. Maltose is a disaccharide sugar which has a sweet
taste- (Something to find out - Are all sugars sweet?). The pH
and temperature of your mouth are also important for this reaction,
as is chewing our food properly before you swallow it to give
the enzymes in your mouth time to do their jobs.
