Wednesday, May 29, 2013
Cell Structure (Short Note)
Wednesday, May 29, 2013 by Faizan Bhatti
In considering the structure of the cell it is essential to relate its parts to its function.
The protoplasm of the cell is composed of a centrally placed body, the nucleus, and the cytoplasm or remainder of the protoplasm, which surrounds the nucleus.
This contains the following essential requirements:
1. Mitochondria: Small, rod-like structure which are closely connected with the catabolic, or respiratory, processes of the cell body.
2. Golgi Apparatus: A canal like structure lying next to the nucleus and involved in the secretory activities of the cell.
3. Ground Cytoplasm: A highly complex colloidal material in which the other structures are embedded. It is highly concerned with the anabolic, or synthetic, activities of the cell.
4. Centrosome: A minute dense part of the cytoplasm, ling close to the nucleus. It plays an important part during cell division.
5. Cell Membrane: The cell boundary is no-static envelope. Many important functions are concerned with it, but in particular it acts as a selective sieve through which certain substances are allowed to pass into the cell, or which prevents other substances from gaining access to it. Thus it is moist important in maintaining the correct chemical composition of protoplasm.
The nucleus consists of a more compact mass of protoplasm, separated from the cytoplasm by the nuclear membrane which is also selectively porous, allowing substances to escape from the nucleus into the cytoplasm or substances to pass into it. The nucleus controls the cell and all its activities. Without a nucleus the cell would die.
The nucleus contains many protein-rich threads lying in nuclear sap. In the ‘resting cell’ the threads are collectively spoken of as chromatin. These threads or chromosomes are vital to the everyday activities of the cell and are responsible for determining the hereditary characteristics of the human body. On the chromosomes in linear arrangement sit the genetic or hereditary determinants, the genes. The number of chromosomes in a body cell is constant for a particular species of organism. In man there are twenty three pairs of forty six chromosomes.
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