1-Sweet
tasting
2-soluble
3-atoms form
a ring shape.
Disaccharide's-
2(CH20)n-H2O
Reactions
Condensation-
Joins molecules
making water.
Hydrolysis-
Separates
molecules
using water.
Glucose- (monosaccharide.)
C6H12O6
alpha-glucose.
Two alpha-glucose monosaccharide's can
join together to make a disaccharide.
alpha-glucose + alpha-glucose:
maltose + water.
Can also go backwards in
a hydrolysis reaction to
form two alpha-glucose
molecules from maltose
and water.
Forms a glycosidic bond
when the hydroxide group
and oxygen are removed to
form a COC bond.
beta-glucose.
Disaccharides
Sucrose
Made from
glucose and
fructose.
Maltose
Made from two
glucose molecules.
Lactose
Made from
galactose
and glucose.
Tests for sugars.
Reducing sugars.
All monosaccharide's
and some
disaccharides are
reducing sugars.
Benedict's Test
1- Add sample to a test tube. 2- Add ten drops
of benedicts reagent. 3- Heat to 90 degrees in a
water baths. 4- Observe a colour change.
If reducing sugars are present then
it will change colour to a red/brown.
Depending on its concentration it
may even turn green, indicating there
is a very low concentration.
Non-reducing sugars.
This test is more complicated as the sugars, if present first
have to be broken down by acid hydrolysis to produce the
reducing sugars like monosaccharide's and some disaccharides.
1- Add sample to a test tube. 2- Add HCl and heat in a water bath (acid
hydrolysis). 3- Leave to cool and add sodium hydrogencarbonate powder to
make to solution neutral. 4- Add ten drops of benedicts reagent and observe
a colour change.
If non-reducing sugars are present
then the colour will change as above.
This test should only be
completed once there is
a negative result for
reducing sugars.
Polysaccharides.
Starch.
Test for starch is to
add iodine. If starch is
present it will turn
brown/black, depending
on concentration.
Made of
alpha-glucose;
they're
unbranched.
They're a good energy
store and respiratory
substrate found in
grains in potato tubers,
seeds and stoma of
chloroplasts.
Properties: Compact, too big to pass through
membranes, insoluble- osmotically inactive,
many glucose molecules, arranged in a helix.
Glycogen
Made of alpha-glucose and found in
humans in the liver and muscles. Also
found in fungi and bacteria.
They're branched
and act as a quick
energy release
stores and
regulate blood
glucose levels.
Properties:
branched,
insoluble
and tightly
coiled.
Cellulose.
Properties: Mechanically
strong, inverted arrangement
of successive glucose
molecules forming hydrogen
bonds, tightly crossed-linked
to form micro fibrils and
fibres, interwoven, gaps allow
permeability.
Made of
beta-glucose;
they're
unbranched.
They're good at maintaining cell wall
turgidity- leaves held in place and
stem flexible but firm in the wind.