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.
Cytoplasm:
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.
Nucleus:
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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