1.1 Starch is a
found in plants in
the form of small
1.1.1 Starch is made up of
chains of α-glucose
linked by glycosidic
bonds that are formed
22.214.171.124 The unbranched
chain is wound into
a tight coil that
1.2 The main role of starch is
energy storage, something
it is suited for because:
1.2.1 ♦ Starch is insoluble so doesn't
draw water into the cells by
126.96.36.199 ♦ being insoluble, it does not
easily diffuse out of cells.
188.8.131.52.1 ♦ It is compact, so a lot of it
can be stored in a small space.
184.108.40.206.1.1 ♦ when hydrolysed, starch forms
α-glucose, which is easily
transported and readily used in
2.1 Starch is never found in
animal cells. Instead, a
glycogen, serves the same
2.1.1 Animal cells get energy from
glucose, but store it as
220.127.116.11 Glycogen has a very similar structure
to starch but has shorter chains and
more side branches; meaning that
stored glucose can be released
quickly which is important for energy
release in animals.
2.2 Glycogen is the major
carbohydrate storage product
of animals and is stored as
small granules in the muscles
2.2.1 Because it is made up of smaller
chains, it is more readily hydrolysed
3.1 Cellulose is made of long,
unbranched chains of β-glucose.
3.1.1 In the β-glucose units, the
positions of the -H group and the
-OH group on a single carbon
atom are reversed; the -OH
group is above the ring.
18.104.22.168 This means that to form
glycosidic links, each β-glucose
molecule must be rotated by
180° compared to its neighbour.
3.2 Cellulose is the major
component of a cell wall
in plants and is what
makes the cell rigid.
3.2.1 The cellulose chains are linked together
by hydrogen bonds to form strong fibres
22.214.171.124 These strong fibres mean cellulose provides
structural support for plant cell walls.
126.96.36.199.1 The cellulose cell wall prevents the cell from bursting
as water enters by osmosis by exerting an inward
pressure that stops any further influx of water.
188.8.131.52.1.1 As a result, living plant cells are turgid and push
against each other, making herbaceous parts of
the plant semi-rigid.
184.108.40.206.1.1.1 This is important to maintain stems
and leaves in a turgid state so they
can provide the maximum surface
area for photosynthesis.
3.3 Cellulose has straight chains
parrallel to each other,
allowing hydrogen bonds to
form cross-linkages between