Describe Physio chemical nature of the cytoplasm of plant cell
The protoplasm
outside the nucleus is called cytoplasm. In some cells e.g. Amoeba, the
cytoplasm has two distinct parts and outer clear ectoplasm and an inner
granular endoplasm in most cell. Under the light microscope cytoplasm appears
as a semi fluid colloid that fills the cell. The cytoplasm exhibits active
streaming movements around the inner surface of the cell. This movement is
known as cyclosis.
Cytoplasm is
composed of several types of organelles occupying as much as half of the volume
of the cell and a fluid matrix, the cytosal. Cytosal is watery solution of
salts, sugar, amino acids, Proteins, fatty acids, nucleotides and other
material. Giving shape and organisation to the cytoplasm it is the network of
Protein fibres, the cytoskeleton s. many of them organelles and individual
molecules of the cytoplasm are thought to be attached to cytoskeletion
observation under electron microscope however reveal that cytoplasm not a
simple colloid since it contains many different kinds of minute organelles are
also a mesh of tiny filaments, the microfibrils that form a sort of skeleton
giving rigidity to cell and helping unicellular organisms in movement.
A variety of
cytoplasmic organelles are present in cells, majority of them are on the basis
of membrane.
Membrane bound organelles:
(i) ENDOPLASMIC RETICULUM
It extends from
plasma membrane to the nuclear membrane. It is an elaborate tube like system of
lipoprotein.
They appear to
be associated with enzyme formation, proteins synthesis, storage and transport
metabolic products. They may also contribute to the formation of cell plate in
nuclear division and of the nuclear membrane around the newly formed nuclei.
(ii) MITOCHONDRIA
They appear as
minute granular vesicles, rodlets, threads or strings. They are the centre of
aerobic respiration. They are called power house of the cell.
(iii) GOLGI APPARATUS (DICOTYOSOME)
This was found
by scientist golgi and was names as Golgi body. Each of them is disc shapedand
ahs central, flattered, plate like cisternae, peripheral network
interconnecting tubules and peripherally occurring vesicles and golgian
vacuoles.
(iv) PLASIDS
They are
protoplasmic membrane bound organelles which function as chemical synthesizers
and storage bodies. They occur in great number in the cell of plants.
Non-membrane bound organelles
(i) RIBOSOMES
They contain
high concentration of Ribonucleic acid (RNA). Ribosomes are associated with the
membrane of the tubes and also occurring free in the cytoplasm and are very
small particles. They synthesize some of the enzymes and are mainly concerned
with protein synthesis.
(ii) CENTRIOLE
In the cytoplasm
near nucleus the cells of certain lower plants possess centriole. Higher plants
generally lack centiole. Each centrosome consists of two cylinders called
centriole lying perpendicular to one another. Each cylinder is composed of nine
parallel triplets of hollow cylindrical microtubules. During cell division the
centriole replicates and moves to opposite side of the cell and thread like
fibres begin to radiate from centriole in all directions called astrial rays.
(iii) VACUOLES
They are
non-protoplasmic liquid filled cavities in the cytoplasm and are surrounded by
a membrane called tonoplast. It is permeable and allows certain substances to
enter in the vacuole. They are more prominent in nature cells. Vacuoles in
plant cells are filled with cell sap and act as store house which often play
role in plant defence which is necessary for plant cell enlargement.
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