Structure Of Cell Doraha(b)

INTRODUCTION All the living organisms which we see are essentially complex structures, made up of numerous co-ordinated compartments usually called as Cells. These organism are made up of one or more cells. These have some basic cellular structure of organization and perform basic similar physiological function. Cell is thus the basic unit of life in living being.

DISCOVERY OF CELL Cell was discovered by Robert hooke in 1665. He studied a thin piece of cork with his crude microscope Hooke described that the cork is made up of hundred of little hexagonal boxes giving a kind of honey comb appearance. He called these little boxes cells. In 1674, Antony Van Leeuwenhoek was the first who observed free cells such as bacteria, spermatozoa and red blood corpuscles under his own designed simple microscope.

TYPES OF CELL • Prokaryotic Cell • Eukaryotic Cell

PROKARYOTIC CELLS They are the cell which have primitive organization of genetic material. Their DNA is not enclosed in a nuclear membrane. These cells do not have a well-defined nucleus. They also lock cell organelles, E.g. Bacteria, blue green algae, human RBC etc.

EUKARYOTIC CELLS In the cell of plants and animals, the genetic material is locked with in nuclear membranebounded organelles such as mitochondria, chloroplasts, loysosmes end oplasmic reticulum etc. in their cytoplasm.

STRUCRUCTURE OF CELL Cells are very small and can not be seen with necked eye. Fine structural details of the cells can only be seen under light microscope that use light and can magnify an object up to 2000 times and electron microscope that use beam of electrons and can magnify things as much as half a million times. A cell is a tiny mass of cytoplasm which is limited by a membrane and capable of capable of performing all functions of life.

Animal Cell and Plant Cell

PARTS OF CELL • • • • • • • • • • •

CELL WALL CELL MEMBRANCE CYTOPLASM NUCLEUS ENDOPLASMIC RETICULAM RIBOSOMES MITOCHONDRIA GOLGI APPARATUS PLASTIDES CENTROSOME VACULONES

CELL WALL It is an outer rigid protective, supportive covering of plant cells. Cell wall is generally considered to be a non-living secretion of the protoplasm but actually it is metabolically active and is capable of growth.

CELL MEMBRANCE Every cell is bounded by a thin, delicate, living and trilaminar membrane called plasma membrane. At molecular level, It consists of a continuous bilayer of lipid molecules with protein molecules embed in it.

CYTIPLASAM The space between the plasma membrane and the nucleus is filled by an amorphous, translucent, homogenous, colloidal liquid called CYTIPLASAMIC matrix. It consists of various inorganic molecules such as water, salts of sodium, potassium, amino acids, carbohydrates, lipids and proteins. In the cytoplasm various cell organelles are found floating.

NUCLEUS The nucleus is an important, centrally located spherical cellular components. It is bounded by two unit membranes, both forming a nuclear envelope. The nuclear envelope contains many pores, the nuclear pores and en closes the liquid ground substance, the nucleoplasm.

ENDOPLASMIC RETICULUM Endoplasmic reticulum is a complex network of membrane bounded tubules that runs through the cytoplasm. At places it is connected with the plasma lemma as well as with the nuclear envelope. It is extensive in metabolically active cells, e.g. pancreas

RIBOSOMS These are found in all cell, both Prokaryotes and Eukaryotes except in mature sperms and RBCs. In prokaryotic cells, they are found floating free in the cytoplasm . In Eukaryotic cells they occur free in the cytoplasm as well as attached to the outer surface of the rough endoplasmic reticulum. Each ribosome has two sub-units a smaller sub-unit and a larger sub-unit and a larger sub-unit a smaller sub-unit. Ribosome's are composed of RNA and protein

MITOCHONDRIA Typically mitochondria are sausage shaped, but these may be granular, filamentous, rodshaped also. Each mitochondria is bounded by two unit membranes – a smooth outer membrane and an inner membrane which is folded inwards to form cristae. The cristae lie in a ground substance matrix. The mitochondrial matrix contains lipids, proteins, circular DNA and RNA.

GOLGI APPARATUS It is present around or above the centrioles in all eukaryotic cells except mammalian RBC’s and mature sperms. It is absent in the prokaryotes. It was discovered by camilo Golgi.

PLASTIDS These organelles are found only in plant cell. Plastids are of three type  chromoplasts  chloroplasts  Leucoplast Stroma

Outer Membrane Inner Membrane

Thylakoid

Granum

CENTROSOME It is a small naked protoplasmic structure present near the nucleus. Centrosome consists of two small granules called centrioles, which lie at right angles to each other. Each centriole is a hollow cylindrical structure made up of nine microtubules. During cell division centrioles migrate to the opposite poles of the cell.

VACUOLES These are fluid filled and membrane bounded spaces. In animal cells vaculoes are smaller in size. In mature plants cells the small vacuoles fuse to a single large vacuole. Vacuoles are bounded by a membrane known as tonoplast.

Govt. Sen. Sec. School, Doraha

Class 9th Ajay Kumar Mohinder Kumar Vishal Jaswinder Singh

BIBLIOGRAPHY • Text Book of Science (P.S.E.B) of Class 9th • Internet