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Current Category » Bio-chemistry

Fat Soluble Plant Pigments

A) Chlorophyll:

a) Chlorophyll “a” (C55H72O5Mg) Ratio in plant is 3: 1
b) Chlorophyll “b” (C55H70O6Mg)

Properties of Chlorophyll “a”:

1. Black colour in solid state and greenish blue in colour in liquid state.
2. Helps in photosynthetic activities.
3. Occurs in protoplasm of the cell, strongly absorbs light in blue and red regions.

Properties of Chlorophyll “b”:

1. It is dark blue colour in solid state, absorbs light not effectively absorbed by chlorophyll `a'.
2. Green colour in liquid state.
3. Occurs in blue algae.

All chlorophyll possesses the property of fluorescence.

Chemical Nature of Chlorophyll Pigments:

They are esters of cornplex dicarboxylic acid (phytol) and derived from porphyrin, a fully conjugated tetrapyrrole. It contains 4 pyrrole groups, 1 Mg atom in the center and 2 ester groups. (Structure Mallette  and  Althouse book)

Physiological Role of Chlorophyll:

Photosynthesis   conversion of solar energy to chemical energy

B) Carotenoid: Carotenoids are tetra terpene (polyene) consisting of eight isoprenoid groups. Carotene (C40OH56)

Occurrence of Carotenoid:

1. Occurs in root of carrot.
2. It is soluble is ether.
3. Always associated with chlorophyll in the chloroplast.

Chemical Nature of Carotenoid:

1. It consists of hydrocarbon.
2. Carotene molecule consists of isoprene unit (C5H8)
3. On hydrolysis yield vit. A. C40H56 + 2H2O hydrolyzed 2C20H29OH, B-carotene  vit. A
4. There are four isomers present in carotene

 


Name of Isomer

% Occurrence

On Hydrolysis Vit A

α Carotene

10% matured green leaves

1 molecule of Vit. A

β Carotene

90% matured green leaves

2 molecule of Vit. A

Gamma Carotene

Very little

1 atm of Vit. A

Lycopene

Red fruits

Not a precusor of Vit. A

Physiological Role of Carotenoids:

1. Protect the chlorophyll and sensitive enzymes in plant from destruction against harmful light radiation.
2. Helps in assimilation process
3. Carotene is a precursor of Vit. A.
4. It consists of terpene which is building block of essential oil.
5. Carotenoid occurs in photochemical reactions in plants.

 

b) Xanthophyll:

(C40H5602) found in leaves, fruits, flowers.
 
1. Yellow colour pigments, contains oxygen in various forms.
2. It is associated with carotene in plants

i) Lutein very important found in many plants
ii) Zeaxanthin matured green leaves of maize and yellow seeds.
iii) Lycoxanthin yellow tomato fruit
iv) Cryptoxanthin- in maize and small quantity in citrus rind.

 

Current Category » Bio-chemistry