What is Cytoplasm of the cell


The Protoplasmic mass of the cell leaving out the nucleus and the plastids is call cell protoplasm or cytoplasm. When the cell is young to cytoplasm completely fills its cavity i.e. the space between the cell wall and the nucleus. As the cell repidly increases in size it cannot keep peace with the growth of the cell wall. Consequently a number of small non protoplasmic cavities appear in the cytoplasm which are called vacuoles. As the cell further increases in size and matures all these small vacuoles fuse together into a large one which then occupies the greater part of the cell pushing the cytoplasm outwards as a thin living layer against the cell wall. 

In some cells comparatively small vacuoles persist and then the cytoplasm forms delicate strands around them. The vacuole is filled with a fluid called cell sap which is water containing a large number of soluble chemical substances such as inorganic salts, organic acids, soluble carbohydrates e.g. sugar, soluble proteins, amino acids and in certain cells, nucilage, anthocyanins, tannins, latex, alkaloids etc in varying proportions. The vacuole is thus a tiny reservoir of the cell from which the cytoplasm draws water and other material according to its need.

They cytoplasm has three distinct parts (1) its outer surface forms an extremely thin and delicate membrane called plasma membrane or ectoplasm. (2) Its middle part is granular and is called the endoplasm; its fluid portion is called hyaloplasm and (3) its innermost part surrounding the vacuole as a thin membrane is called the vacuole membrane of tonoplasm. The ectoplasm controls the entrance and exit of water and many chemical substances into and out of the cell, the tonoplast does the same in respect of the vacuole, while the endoplasm performs the general function of the cytoplasm. The membranes are hyaline in nature and are made up of lipoproteins. Cytoplasm includes various substances like plastids, endoplasmic reticulum, ribosomes chondriosomes, golgi bodies, centrosomes and ergastic substances.

Kolliker in 1862 gave the name cytoplasm to the substance found around the nucleus. The cytoplasm usually consists of water which may be 85 to 90 percent in it. Many organic and inorganic substances also occur in the cytoplasm either in true solution or in colloidal state. Salts, carbohydrates and other water soluble substances are found in dissolved state. Proteins and fats are also found in the form of very minute particles which are invisible in the microscope of ordinary light. They are found in colloidal state. The cytoplasm remains always in dynamic state due to constant phase inversions. It is bounded by a non molecular or multi-molecular layer on the outside called ectoplasm or plasma membranes while the layer on inside called tonoplast or the vacuolar membrane. The protoplasmic layers are semi permeable in nature which involve in differential absorption. In the cytoplasm the fatty substances such as lipids and certain proteins take part in the formation of plasma membrane. The vacuolar membrane also develops from the same substance and possesses similar structure to that of plasma membrane.

Comments

Post a Comment

Popular posts from this blog

What is the Dynamic Theory of Profit

Image
Clark's Dynamic Theory of Profit And Its Criticism The Dynamic Theory of Profit is associated with the name of an American Economist, J. B. Clark. In the world of reality, according to J. B. Clark, profit arises only in a dynamic economy. An economy is said to be dynamic when there is a change in population growth or change in the method of production or a change in the consumer’s wants, etc. A society which is without these changes is called a static society. In a static society, only monopoly profits continue to exist. All other economic profits are gradually eliminated by competition. In a dynamic society, an entrepreneur is always confronted with continuous unpredictable changes in demand for his product. The variation in demand may take place due to changes in fashions, tastes, the standard of living, distribution of income, population, new inventions, international repercussions, technological advances, etc. A prudent entrepreneur will always keep an eye on future demand
Read more

Compare the anatomy of Bifacial and Isobilateral leaves

BIFACIAL LEAF: It is also called dorsiventral leaf. This leaf is more strongly illuminated on upper surface than on lower surface. This unequal illumination induces a difference in the internal structure between upper and lower sides. Its internal structure shows: (1)        Upper Epidermis This is single layer of cells with thick cuticle which checks excessive evaporation of water from the surface. It does not contains chloroplasts, stomata are also absent. (2)        Lower Epidermis This is also single layer but with a thin cuticle. It bears many stomata, two guard cells of which contain some chloroplast, none are present in the epidermal cells. Internal to each stomata is large cavity called respiratory cavity. Lower epidermis of leaf is meant for exchange of gases (oxygen and carbon dioxide) between the atmosphere and the plant body. Excess water also evaporates from lower epidermis. (3)        Mesophyll The ground tissue lying between upper epidermis and th
Read more

osmoregulation in terrestrial and aquatic animals

Mechanism of osmoregulation is very important for all groups of animals whether inhibting land or water. Unlike plant cells, animal cells when placed in hypotonic solution burst due to the continuous absorption of water. On the contrary they would shrink and die if constantly placed in hypertonic solution. Normally uptake and loss of water are in balance for proper survival of cell. (1)        Osmoregulation in terrestrial animals: Terrestrial animals are more likely to loose water by evaporation through their permeable surfaces exposed to amsophere. Among various animal groups only Arthropods and vertebrates became the most successful land dwellers. They have developed number of strategies to maintain osmoregulation of their body fluid. (a) Water proof external coverings: To prevent water loss through external surfaces, vertebrates like reptiles, birds and mammals have water proof keratinized epidermis. Similarly the insects have developed external water proof layer called
Read more