Lab Session 6Lab Session 6

IUG, 2012TMZIUG, 2012TMZ

Analysis of pigments and Oxidation processes in photosynthetic organisms

Analysis of pigments and Oxidation processes in photosynthetic organisms

1. Photosynthetic Organisms1. 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. Chlorophyllsb.Phycobilinsc. Carotinoids

2. Animal and plant cells2. 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…In plants…

A number of high actively enzymes called oxidases is observed:

1.Peroxidases2.Polyphenoloxidases

Such enzymes are involved in oxidation of secondary metabolites

Color reactions for plant pigmentsA. extraction of pigments from nettle leaves

Color reactions for plant pigmentsA. extraction of pigments from nettle leaves

PrinciplePigments 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 KrausB. Separation of pigments according to Kraus

• PrincipleDifferent pigments have different solubility in petroleum ether.Chlorophyll and chlorophyllide are soluble, while xanthophyl insoluble

C. Precipitation of chlorophyllC. 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 acidD. Reduction of chlorophyll with ascorbic acid

• PrincipleAscorbic acid can reduce chlorophyll that forms a yellow color in a reduced form state.

E. Formation of Pheophytin from chlorophyllE. Formation of Pheophytin from chlorophyll

• PrincipleHydrochloric acid can bind to Mg2+ of chlorophyll, to produce a Pheophytin that has an olive-brown color.