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CELL ORGANELLES and CELL DIVISION





Cell Structure cont..

CELL ORGANELLES:

Organelles are small structures scattered in the cytoplasm that work together to carry out life processes.
There are various types of cell organelles that perform different functions. Some of these are as follows:

MITOCHONDRIA:

Mitochondria are small rod-like structures. They provide energy in the form of ATP. Therefore, they are known as powerhouse of the cell.

RIBOSOMES:

Ribosomes are tiny structure found either attached to the surface of endoplasmic reticulum or scattered in the cytoplasm. Ribosomes are associated with protein synthesis.

PLASTIDS:

Plastids are disc-shaped structures present only in plant cells. They can be of three types-chloroplasts, chromoplasts and leucoplasts.

GOLGI BODIES:

The cytoplasm contains a large number of membranous sacs- like structures called Golgi bodies. They are concerned with secreting useful substances such as enzymes and hormones.

VACUOLES:

Vacuoles are sac-like structures in the cell. In mature plant cells, they occupy most of the space within the cell and help to store food, water and wastes. In animal cells, vacuoles are smaller and may be greater in number. They help in waste removal and digestion.

ENDOPLASMIC RETICULUM:

The endoplasmic reticulum is a network of membranous tubes that connect the cell membrane with the nuclear membrane. The endoplasmic reticulum helps to transport substances in and out of cells.

CENTRIOLES AND CENTROSOMES:

The centrioles and centrosomes play an important role in cell division. They are present only in animal cells and are absent in plant cells.

LYSOSOMES:

Lysosomes are called as suicidal bags. They are small rounded sacs filled with tissue dissolving enzymes. They help in the digestion of foreign bodies and worn out cell parts.

CELL DIVISION:

A cell is very small when it is formed. On receiving nutrition, it grows and reaches a certain size after which it divides to form two cells. This process is known as cell division, and the cells formed are known as daughter cells. Cell division is also necessary for replacement of dead cells. Million of cells are die and replaced every second in our body.
COMPARISON BETWEEN ANIMAL AND PLANT CELLS:
S.No Animal Cell Plant Cell
1 Smaller in size larger in size
2 Cell membrane is present but Cell wall is absent both cell membrane and cell wall are present
3 plastids are absent plastids are usually present
4 Vacuoles are smaller and more in number One large vacuole is present in the cell
5 Centrioles, centrosomes and lysosomes are present Centrioles, centrosomes and lysosomes are absent




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