Most carbohydrates are
large and complex chains of
monosaccharides, however
single monosaccharides are
also carbohydrates.
Glucose is a
monosachharide with 6
carbon atoms, and comes in
two types, alpha and beta
glucose. Learn them.
Glucose's structure relates
to its function as the main
energy source in animals. It is
soluble so can be easily
transported, and it's bonds
contain a lot of energy.
DISACCHARIDES
Monosaccharides join
together by condensation
reactions and form glycosidic
bonds. A hydrogen atom on
one monosaccharide bonds to
the hydroxyl group on the
other, releasing a water
molecule.
The reverse reaction is a
hydrolysis reaction, where a
molecule of water reacts with
the glycosidic bond breaking it
apart. Two monosaccharides
make a disaccharides.
Two a-glucose molecules
join together to form maltose,
B-glucose and galactose
form lactose with a 1-4
glycosidic bond, and
a-glucose and fructose for
sucrose with a 1-2 glycosidic
bond.
POLYSACCHARIDES
Starch - The main energy storage in plants
Cells get energy from
glucose, plants store excess
glucose as starch, which is
broken down when in need of
energy, starch is a mixture of
the polysaccharides amylose
and amylopectin.
Amylose - A long
unbranched chain of
a-glucose, consisting of 1-4
glycosidic bonds, the angle of
these bonds give amylose a
coiled structure. Making it
compact and therefore good
for storage.
Amylopectin - A long
branched chain of a-glucose
consisting of 1-4 glycosidic
bonds, and 1-6 glycosidic
bonds. These branches
allow energy to be released
quickly, It is also very
compact. Its a large
molecule so stores a lot of
energy. Starch will not swell
through osmosis as it is
insoluble.
Glycogen - The main energy storage material in animals
Similar to starch animal
cells get energy from
glucose, however it is
stored in glycogen, another
polysaccharide of a-glucose
Its structure is similar to
amylopectin, having 1-4 and
1-6 glycosidic bons, but it
has far more side branches
so that stored glucose can
be quickly released and
energy can get into animal
cells quicker, important for
energy release in animals.
Again it is a large but
compact molecule, so it
stores a lot of energy.
Like starch, glycogen's also
insoluble in water, so it doesn't
cause cells to swell by
osmosis.