Pages in this set

Page 1

Preview of page 1
Water!

- A water molecule ­ H2O is covalently bonded (share electrons)
- Because shared electrons are pulled towards the oxygen
the hydrogen atoms are slightly positive (+ ) and the
oxygen atom is slightly negative (- ) which makes the
molecule polar
- The negatively charged oxygen atoms on…

Page 2

Preview of page 2
helps water to flow making it excellent for transporting substances
- water is a good solvent (can surround ions)

Carbohydrates!

Release energy, cell wall in plants (cellulose) and energy store (starch in
plants, glycogen in animals)
Are large complex molecules made of long chains of monosaccharide's

Glucose ­ monosaccharide with…

Page 3

Preview of page 3
Carbohydrates!

Monosaccharide's are joined together by glycosidic
bonds
During synthesis a H atom on one monosaccharide
bonds with an OH group on the other and a molecule of
H20 is produced (condensation)
In reverse a molecule of water reacts with the glycosidic
bond causing it to break (Hydrolysis)

A disaccharide…

Page 4

Preview of page 4
A polysaccharide is where more than two monosaccharides join together ­ many
-glucose molecules = amylose

Carbohydrates!

Starch ­ main energy storage material in plants
- cells get energy from glucose, plants store energy as starch
- starch is a mixture of two polysaccharide -glucose chains


- Amylose ­ long,…

Page 5

Preview of page 5
- starch is insoluble in water so it doesn't cause water to enter cells by osmosis

Carbohydrates!

Glycogen ­ main energy storage material in animals
- cells get energy from glucose but store with glycogen.
- similar in structure to amylopectin ­ branched = quick
energy release
- Compact =…

Page 6

Preview of page 6
- linked by H-Bonds to form strong microfibrils = structural



Carbohydrates!
Tests for the presence of carbohydrates:

Starch test ­ add a solution of iodine in potassium iodide to the sample. Result if starch is present =
colour change from yellow-brown to Blue-Black.
Reducing sugars ­ all monosaccharide and disaccharide…

Page 7

Preview of page 7
o Carry out the reducing sugar test again ­ if sucrose is present the result will now be positive because
glucose and fructose monosaccharide's are present


Carbohydrates!

Using calorimetry to determine glucose concentration

A calorimeter measures the amount of light absorbed by a solution. The more concentrated
the colour of…

Page 8

Preview of page 8
known concentrations, filtering them and using the calorimeter to measure absorbance. The
results are then plotted on a graph.
Unknown solutions are then tested in the same way


Lipids!
Triglyceride ­
- One glycerol molecule
+ three fatty acids
- Tails are hydrophobic
and so lipids are
insoluble in water.…

Page 9

Preview of page 9
Phospholipids ­ lipids in cell membranes
- same structure as triglycerides except that one fatty acid chain is replaced by a phosphate group
- The phosphate group is ionised = hydrophilic while the tail is still hydrophobic.
Cholesterol ­ often found in cell membranes = hydrocarbon ring attached to HC…

Page 10

Preview of page 10
n
e
n
e
r
g
y
w
h
ic
h
is
r
e
l
e
a
s
e
d
a

10

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »