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Mind Map by Lauren Doyle, updated more than 1 year ago
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Created by Lauren Doyle
about 10 years ago
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10.3 Starch, Glycogen & Cellulose
- Starch
- Starch is a
polysaccharide
found in plants in
the form of small
grains.
- Starch is made up of
chains of α-glucose
monosaccharides
linked by glycosidic
bonds that are formed
by condensation
reactions.
- The unbranched
chain is wound into
a tight coil that
makes the
molecule very
compact.
- The unbranched
chain is wound into
a tight coil that
makes the
molecule very
compact.
- Starch is made up of
chains of α-glucose
monosaccharides
linked by glycosidic
bonds that are formed
by condensation
reactions.
- The main role of starch is
energy storage, something
it is suited for because:
- ♦ Starch is insoluble so doesn't
draw water into the cells by
osmosis.
- ♦ being insoluble, it does not
easily diffuse out of cells.
- ♦ It is compact, so a lot of it
can be stored in a small space.
- ♦ when hydrolysed, starch forms
α-glucose, which is easily
transported and readily used in
respiration.
- ♦ when hydrolysed, starch forms
α-glucose, which is easily
transported and readily used in
respiration.
- ♦ It is compact, so a lot of it
can be stored in a small space.
- ♦ being insoluble, it does not
easily diffuse out of cells.
- ♦ Starch is insoluble so doesn't
draw water into the cells by
osmosis.
- Starch is a
polysaccharide
found in plants in
the form of small
grains.
- Glycogen
- Starch is never found in
animal cells. Instead, a
similar α-glucose
polysaccharide, called
glycogen, serves the same
role.
- Animal cells get energy from
glucose, but store it as
glycogen.
- 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.
- 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.
- Animal cells get energy from
glucose, but store it as
glycogen.
- Glycogen is the major
carbohydrate storage product
of animals and is stored as
small granules in the muscles
and liver.
- Because it is made up of smaller
chains, it is more readily hydrolysed
to α-glucose.
- Because it is made up of smaller
chains, it is more readily hydrolysed
to α-glucose.
- Starch is never found in
animal cells. Instead, a
similar α-glucose
polysaccharide, called
glycogen, serves the same
role.
- Cellulose
- Cellulose is made of long,
unbranched chains of β-glucose.
- 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.
- This means that to form
glycosidic links, each β-glucose
molecule must be rotated by
180° compared to its neighbour.
- This means that to form
glycosidic links, each β-glucose
molecule must be rotated by
180° compared to its neighbour.
- 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.
- Cellulose is the major
component of a cell wall
in plants and is what
makes the cell rigid.
- The cellulose chains are linked together
by hydrogen bonds to form strong fibres
called microfibrils.
- These strong fibres mean cellulose provides
structural support for plant cell walls.
- 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.
- As a result, living plant cells are turgid and push
against each other, making herbaceous parts of
the plant semi-rigid.
- This is important to maintain stems
and leaves in a turgid state so they
can provide the maximum surface
area for photosynthesis.
- This is important to maintain stems
and leaves in a turgid state so they
can provide the maximum surface
area for photosynthesis.
- As a result, living plant cells are turgid and push
against each other, making herbaceous parts of
the plant semi-rigid.
- 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.
- These strong fibres mean cellulose provides
structural support for plant cell walls.
- The cellulose chains are linked together
by hydrogen bonds to form strong fibres
called microfibrils.
- Cellulose has straight chains
parrallel to each other,
allowing hydrogen bonds to
form cross-linkages between
adjacent chains.
- Cellulose is made of long,
unbranched chains of β-glucose.
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