Download Lab Session 6

Lab Session 6
IUG, 2012
TMZ
Analysis of pigments and Oxidation processes
in photosynthetic organisms
1. Photosynthetic Organisms
They contain an operative system that can
selectively trap the visible light and use it in
production of energy in form of ATP:
This operative system includes:
a. Chlorophylls
b. Phycobilins
c. Carotinoids
2. Animal and plant cells
• In mitochondria of animal and plant cells , the
energy is produced in a similar system
(respiratory chain), where there are specific
enzymes responsible for the production of
energy
In plants…
A number of high actively enzymes called
oxidases is observed:
1. Peroxidases
2. Polyphenoloxidases
 Such enzymes are involved in oxidation of
secondary metabolites
Color reactions for plant pigments
A. extraction of pigments from nettle leaves
Principle
Pigments such as chlorophyll and others have
the property to dissolve in hot ethanol
 Reacting with ethanol, chlorophyll is
converted to ethylchlorophyllide (an ester in
which the phytol is replaced by the ethanol)
B. Separation of pigments according to Kraus
• Principle
Different pigments have different solubility in
petroleum ether.
Chlorophyll and chlorophyllide are soluble,
while xanthophyl insoluble
C. Precipitation of chlorophyll
• Principle
• Chlorophyll ester groups are able to form a
water-insoluble barium salts of chlorophyllide
a & b on saponification with barium hydroxide
solution
Supernatant liquid has a yellow color due to
the presence of carotene and xanthophyll.
D. Reduction of chlorophyll with ascorbic acid
• Principle
Ascorbic acid can reduce chlorophyll that
forms a yellow color in a reduced form state.
E. Formation of Pheophytin from chlorophyll
• Principle
Hydrochloric acid can bind to Mg2+ of
chlorophyll, to produce a Pheophytin that has
an olive-brown color.