Monday, April 16, 2012

Uses of pigments in living organism and non-living organism

Uses of pigments

1.In human being and animals

The natural pigment in the living organism plays a very crucial role in their daily life. Most common pigment presents in human and animal’s skin is known as melanin. Melanin is used to protect human being and animals from sunburn due to the ultraviolet radiation from sunlight. Eumelanin (one types of melanin) is the pigment which is mainly concerned with the protection of skin by absorbing the incoming ultraviolet radiation. The concentration of eumelanin will increase after more exposure of skin towards ultraviolet light. As a result, the skin becomes darker because it tends to protect the skin from damage. Some individual humans and animals have very little or lack of this pigment in their bodies is known as albinism (skin disease). In the diagram 3, the process explains the formation of melanin and the effect of lack of this pigment in the body.


Diagram 3 Formation of melanin process and the effect of lack of melanin

In addition, the biological pigment present in some of the animals especially prey are used to protect themselves from the hunting of predators. The biological pigment can imparts the colour of their physical appearances similar with the colour of surrounding environment such as rock, sand and leaf in order to make them difficult to be spotted by predators. For example, grasshopper and porcupines are using their pigment to protect themselves. This phenomenon that happens within the body living organism is known as camouflage (Diagram 4).


Diagram 4 Camouflage of grasshopper

Besides, the pigments present in animals are also used in mimicry in which one animal mimics the other one’s physical appearance in order to protect themselves from the predators. Normally, a palatable or harmless species will tend to mimic an unpalatable or harmful species. Mimicry between eastern coral snake and scarlet king snake in Carolinas is a good example to explain the importance of biological pigment in animals. Both species live in Carolinas, but the kingsnake is also found in regions without poisonous coral snakes. The predators that inherit an avoidance of coral snake’s colouration and hence they will attack less often towards the scarlet king snake in the regions where coral snake could be found.


Diagram 5 Mimicry between eastern coral snake and scarlet king snake

The biological pigments that present naturally in the animals are very important in mate selection in animals. This is because some of the female animals will choose the male animals as their partners based on the colourful appearances of the male animals. In the mate selection of peacocks, the female peacocks are always attracted by the peacocks possesses a colourful feather and tail.


Diagram 6 Peacock is wooing a peahen

2. In plants

For plant, the natural pigment is playing a very important role for their survival. Chlorophyll is the green pigment that is very essential for all the plants to carry out the photosynthesis. This is because chlorophyll can absorb the energy at certain wavelength from the sunlight in which it induces photosynthesis to takes place. Photosynthesis is a process that absorbs energy from sunlight to convert carbon dioxide and water to produce glucose and oxygen. Hence, pigment is very important for all the plants to survive.

Moreover, the presence of pigment in plants such as anthocynin(appears as red, blue or purple in plants) makes them to have colourful appearances. In order to attract pollinators, the colour of the flowers must be presentable and attractive and so that pigment is very determinative for plants. Pollination is a process of pollen transferring in plant reproduction and therefore enabling fertilization and sexual reproduction in plants. In flowers, the bright red and purple characteristic is adaptive for attracting insects or animals for pollinations. Anthocynin is also important in the fruits. This is because colourful skin of the fruits can attract the attention of animals and then the seeds could be dispersed into other area once the fruits are eaten by the animals.


Diagram 8 A European honey collects nectar while the pollen is collected by its body

Last but not least, the pigment found in the plants can act as an antioxidant in order to protect the plants from oxidation of free radical. The pigment is called carotenoids. Sunlight tends to induce the formation of free radical in the atmosphere in which they will destroy the plant structure by oxidizing the protein, DNA and photosynthesis structure of plants. The carotenoids participate in the energy transfer process in order to protect the plants from auto-oxidation. In non-photosynthesizing organisms, such as humans, carotenoids have been linked to oxidation-preventing mechanisms. For example, carotenoids tend to absorb or quench the energy of excited molecules such as singlet state oxygen and triplet state chlorophyll, thereby preventing the destruction of protein, DNA and the photosynthetic apparatus.

3. In application of painting industry and food dye

Pigment is also being widely used in the painting industry to apply on the textile, fabrics, cosmetic, plastic, paper and various materials. The pigment could be the biological pigment extracted from plants, organic pigment and inorganic pigment that synthesized chemically from metallic elements or found naturally. Pigment is one of the components of paint. Pigment serves two functions:

I. Providing colours

II. Protective function for surface underneath of paint and binder from destroyed by ultraviolet light

Pigment is a coloring material usually a finely ground powder which does not dissolve and it is suspended in a liquid solvent to become the coloring material in paint. In organic pigment, the colours are caused by the light energy absorbed by the delocalization of π electron conjugated system. However, the π electron will not absorb all the wavelength of light, therefore the unabsorbed light will be appears as the colours of paints. Inorganic pigments are being applied in paints due to their selectively wavelength absorption properties. During the formation of metal complexes, the transition of electron allows absorption of light energy at different wavelength to occur and so that inorganic pigments can also exhibit in many colours. Hence, colourful organic pigments and inorganic pigments are widely used in painting materials.

The extracted biological pigment in animals and plants can be applied in the food colourings. Some of the artificial pigment which is harmless to human body sometimes can be used in food colourings. In order to produce colourful and attractive food products, pigments are being used in the beverages, baked goods, dairy products, pet foods, and a variety of other products. Pigments can be used to increase the attractiveness and physical appearances of products and hence the products can have a higher market value. For example, the bright purplish-red pigment of the red dragon fruit is an excellent source of natural betanin.

4. In medical uses and health supplement

Nowadays, most the pigment extracted from the plants can be used in the manufacture of nutrient supplement in the current market. This is because the pigment that found in the plants such as carotenoids (beta-carotene and lycopene) can act as an anti oxidizing substance. This antioxidant can against the free radical that present in the atmosphere. Beside that, beta-carotene that found abundantly in carrot can be used to promote healthy eyesight of humans. For those people who have night blind can take this supplement in order to improve their eyesight at night.

Other that that, a derivative from chlorophyll which is named as chlorophyllin can be used in medicine for wound healing. The chlorophyllin is used to promote wound healing process and hence this can reduce the risk of patient to getting infection or inflammation which causes fatal.

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