- Introduction
- Rest time! Have fun
- Physics
- Chemistry
- BIOLOGY
- Reaching the age of Adolescence
- CROP PRODUCTION AND MANAGMENT
- Cells : The basic structural unit of life
- Nutrition in human beigns
- RESPIRATION IN HUMAN BEIGNS
- TRANSPORTATION IN HUMAN BEIGNS
- excretory system in human beigns
- NERVOUS SYSTEM
- PHOTOSYNTHESIS
- Respiration in plants
- REPRODUCTION IN PLANTS
- MOVEMENTS IN PLANTS
- Forest our lifeline
- WASTE WATER STORY
- WEATHER,CLIMATE AND ITS ADAPTATION .
- Reaching the age of Adolescence
- Model tests
- Animation time
Cell: Structural Unit Of Life
CELL-
The basic structural unit of life is known as cell.
A group of cell form a tissue.
A group of tissues form a Organ.
A group of form a system.
Study of cells is known as Cytology.
Discovery of Cell-
Robert Hooke in 1665 discovered cell by observing cork cell.
He saw compartments and termed it as CELLULAE.
He observed that each cell was separated from another by a wall.
Multicellular organisms
The organisms which have more than two cells .
Eg- Humans
Aspergills
Unicellular organism-
The organism which have only one cell.
Eg- Amoeba
Paramecium
Acellular organisms
The organisms which do not have any cells.
These organisms are living only in its Host organism.
Eg- Virus
Size of Cells
The size of cells in living organisms maybe as small as a millionth of a metre(micrometre or micron) or may be aslarge as a few centimetres. However, mostof the cells are microscopic in size andare not visible to the unaided eye. Theyneed to be enlarged or magnified by amicroscope. The smallest cell is 0.1 to0.5 micrometre in bacteria. The largest cell measuring 170 mm ×130 mm, isthe egg of an ostrich.
PARTS OF A CELL
Cell Membrane-
The membrane separates cells from one another and also the cel l f rom the surrounding medium. The plasma membrane give definite shape to a cell. It is also known as Plasma Membrane.
Cytoplasm-
Cytoplasm is the jelly-like substance present between the cell membrane and the nucleus. Various other components, ororganelles, of cells are present in the cytoplasm.
There are two types of cell organelles they are -
1. Membranous organelles
2. Non-Membranous organelles
1. Membranous organelles -
These are organelles bounded by membrane.Some organelles are as follows-
(a) Endoplasmic retiiculum
It is scattered through out the cytoplasm.
It extends from plasma membrane to nucleus.
It forms cytoskeleton and provides mechanical support.
It helps in transportation of substance from one part to another part of cell.
(b) Golgi body
(c) Vacuoles-
They are storage areas in the cells.
Its watery fluid is known as cell sap.
It is surrounded by TONOPLAST.
(d) Mitochondria-
They are rod shaped bodies.
It contains proteins , lipids , D.N.A and R.N.A .
They are called POWER HOUSES OF CELLS.
(e) Chloroplasts-
(f) Lysosomes-
They are known as SUICIDAL BAGS of a cell.
2. Non-Membranous organelles-
These organelles are not bounded by membranes.
(a) Ribosomes-
They contain R.N.A and protein.
They are called Protein factories of a cell.
(b) Centrioles
Nucleus
It is an important component of the living cell. It is generally spherical and located in the centre of the cell. It can be stained and seen easily with the help of a microscope. Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus. W i t h a m i c r o s c o p e o f h i g h e r magnification, we can see a smaller spherical body in the nucleus. It is called the nucleolus. In addition, nucleus contains thread-like structures called chromosomes. These carry genes and h e l p i n i n h e r i t a n c e o r t r a n s f e r o fcharacters f rom the parents.
Prokaryotic and Eukrayotic animals
The nucleus of the bacterial cell is not well organised like the cells of Multicellular organisms. There is no nuclear membrane. The cells having n u c l e a r m a t e r i a l w i t h o u t n u c l e a r membrane are termed prokaryotic cells. The organisms with these kinds of cells are called prokaryotes (pro : primitive; karyon : nucleus). Examples are bacteria and blue green algae. The cells, like onion cells and cheek cells having well organised nucleus with a nuclear membrane are designated as eukaryotic cells. All organisms other than bacteria and blue green algae are cal led eukaryotes. (eu :true; karyon: nucleus)
The basic structural unit of life is known as cell.
A group of cell form a tissue.
A group of tissues form a Organ.
A group of form a system.
Study of cells is known as Cytology.
Discovery of Cell-
Robert Hooke in 1665 discovered cell by observing cork cell.
He saw compartments and termed it as CELLULAE.
He observed that each cell was separated from another by a wall.
Multicellular organisms
The organisms which have more than two cells .
Eg- Humans
Aspergills
Unicellular organism-
The organism which have only one cell.
Eg- Amoeba
Paramecium
Acellular organisms
The organisms which do not have any cells.
These organisms are living only in its Host organism.
Eg- Virus
Size of Cells
The size of cells in living organisms maybe as small as a millionth of a metre(micrometre or micron) or may be aslarge as a few centimetres. However, mostof the cells are microscopic in size andare not visible to the unaided eye. Theyneed to be enlarged or magnified by amicroscope. The smallest cell is 0.1 to0.5 micrometre in bacteria. The largest cell measuring 170 mm ×130 mm, isthe egg of an ostrich.
PARTS OF A CELL
Cell Membrane-
The membrane separates cells from one another and also the cel l f rom the surrounding medium. The plasma membrane give definite shape to a cell. It is also known as Plasma Membrane.
Cytoplasm-
Cytoplasm is the jelly-like substance present between the cell membrane and the nucleus. Various other components, ororganelles, of cells are present in the cytoplasm.
There are two types of cell organelles they are -
1. Membranous organelles
2. Non-Membranous organelles
1. Membranous organelles -
These are organelles bounded by membrane.Some organelles are as follows-
(a) Endoplasmic retiiculum
It is scattered through out the cytoplasm.
It extends from plasma membrane to nucleus.
It forms cytoskeleton and provides mechanical support.
It helps in transportation of substance from one part to another part of cell.
(b) Golgi body
(c) Vacuoles-
They are storage areas in the cells.
Its watery fluid is known as cell sap.
It is surrounded by TONOPLAST.
(d) Mitochondria-
They are rod shaped bodies.
It contains proteins , lipids , D.N.A and R.N.A .
They are called POWER HOUSES OF CELLS.
(e) Chloroplasts-
(f) Lysosomes-
They are known as SUICIDAL BAGS of a cell.
2. Non-Membranous organelles-
These organelles are not bounded by membranes.
(a) Ribosomes-
They contain R.N.A and protein.
They are called Protein factories of a cell.
(b) Centrioles
Nucleus
It is an important component of the living cell. It is generally spherical and located in the centre of the cell. It can be stained and seen easily with the help of a microscope. Nucleus is separated from the cytoplasm by a membrane called the nuclear membrane. This membrane is also porous and allows the movement of materials between the cytoplasm and the inside of the nucleus. W i t h a m i c r o s c o p e o f h i g h e r magnification, we can see a smaller spherical body in the nucleus. It is called the nucleolus. In addition, nucleus contains thread-like structures called chromosomes. These carry genes and h e l p i n i n h e r i t a n c e o r t r a n s f e r o fcharacters f rom the parents.
Prokaryotic and Eukrayotic animals
The nucleus of the bacterial cell is not well organised like the cells of Multicellular organisms. There is no nuclear membrane. The cells having n u c l e a r m a t e r i a l w i t h o u t n u c l e a r membrane are termed prokaryotic cells. The organisms with these kinds of cells are called prokaryotes (pro : primitive; karyon : nucleus). Examples are bacteria and blue green algae. The cells, like onion cells and cheek cells having well organised nucleus with a nuclear membrane are designated as eukaryotic cells. All organisms other than bacteria and blue green algae are cal led eukaryotes. (eu :true; karyon: nucleus)