what are Plastics ? describe two major types of plastic. give one example in eavh case.
Answers
Answer:
Plastics are usually classified by their chemical structure of the polymer's backbone and side chains. Plastics can also be classified by the chemical process used in their synthesis, such as condensation, polyaddition, and cross-linking. There are two types of plastics: thermoplastics and thermosetting polymers.
Thermoplastics are the plastics that, when heated, do not undergo chemical change in their composition and so can be molded again and again. Examples include: polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC).
Answer
Plastid is a membrane-bound organelle found in the cell of plants, algae and few eukaryotic cells.
It the site of production and storage of important chemical compounds which are used by the cells of autotrophic organisms.
They contain pigments which are used in photosynthesis and the types of pigments determine the cell's colour.
The types of plastids are-
1) Chloroplasts:- are the green plastids which contain chlorophyll pigments for photosynthesis.
2) Chromoplasts:- are the coloured plastids for pigment synthesis and storage.
The pigment present in them is carotene which gives a different colour to fruits and flowers.
3) Gerontoplasts:- are the chloroplasts that are going through the ageing process.
These are present in the leaves in which no more photosynthesis occurs (such as in the fall months).
4) Leucoplasts: are the colourless plastids for monoterpene synthesis found in non- photosynthetic parts of the plants.
They are of three types:-
a) Amyloplasts- stores starch.
b) Proteinoplasts- stores proteins.
c) Elaioplasts- stores fats and oils.