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Cells and Tissues

THE CELL
The cell is the basic, structural and functional unit of living organisms. There are two types of cells:
a.      
           ANIMAL CELL
b.      PLANT CELL

PARTS OF THE CELL AND THEIR FUNCTIONS
Ø  NUCLEUS: It is usually found in the centre of the cell. It contains nucleolus which is rich in REBONUCLEIC ACID (R.N.A) and chromosomes which is made up of DEOXYRIBONUCLEIC ACID(D.N.A).

FUNCTIONS:
·         It is the power house of the cell. That’s it control all the metabolic activities in the cell.
·         It stores hereditary materials in the cell
·         It is responsible for cell division.

Ø  CELL MEMBRANE/ PLASMA MEMBRANE: It is a thin- flexible semi-permeable membrane which forms a boundary around the cell.
FUNCTIONS:
·         It prevents the cell from injury
·         It is a channel through which substances enter or live the cell
Ø  VACOULE: It is a sac containing watery fluid. It normally occupies a large volume of the cell.

FUNCTIONS:
·         It is used to store foods in the cells
·         It stores waste products of individual cell
·         It imparts colour of food and flowers

Ø  MITOCHONDRION: It is a sausage shaped organelle that is responsible for the breaking of food to release energy.

FUNCTIONS:
·         It produces energy from respiration
·         It is responsible for the synthesis of amino acids
·         It responsible for the synthesis of chlorophyll in plants. 

Ø  CELL WALL: It is made up of cellulous and found outside the cell membrane of plant cells.

FUNCTIONS:
·         It supports and protects the plants
·         It gives the cell its definite shape

Ø  CHLOROPLAST: These are small bodies containing the green-pigment call chlorophyll, which enable plants to manufacture their own food. 

Ø  CYTOPLASM: It is a transparent fluid which contains smaller parts of the cell call organelles.

FUNCTIONS:
·         All chemical reactions and life processes take place in the cytoplasm
·         It helps in the inter-cellular distribution of \molecules, enzymes and nutrients.
·         It helps in the breakdown of glucose. 

DIFFERENCES BETWEEN PLANT CELL AND ANIMAL CELL
PLANT CELL
ANIMAL CELL
It has a cell wall
It has no cell wall
It has chlorophyll
It has no chlorophyll
It has a definite shape
It does not have a definite shape
It has a large vacuole
It has a small vacuole
It stores food as starch
It stores food as glycogen

SPECIALIZED CELLS:
These are cells structurally adopted to perform specific functions. Some examples of specialized cells include the following:
Examples of specialized cells and functions:
Cell
Function
Muscle cell
Relaxes and contracts to produce movement
Red Blood Cell
Carry oxygen from lungs to tissue
White Blood Cell
Produces antibodies to fight against diseases
Nerve Cell
Transmit nerve impulses
Sperm Cell
Fertilizes egg
Palisade Cell
Contains chlorophyll to carry out photosynthesis
Leaf epidermal cell
Allow light to enter the leaf and reach photosynthetic tissues below them.

TISSUE
A tissue is a group of similar cells, which are specialized and perform the same function. Example include Nerve tissue, blood tissue, vascular tissue, etc. 

SOME TYPES OF TISSUES AND THEIR FUNCTIONS
TISSUE
FUNCTION
Adipose tissue
It insulates the body against heat.
Muscle tissue
It contracts and relaxes to bring about movement
Skeletal tissue
It provides support for the body
Nerve tissue
It conducts and co-ordinates impulse messages
Photosynthetic tissue
It produces food
Phloem tissue
It transports food
Epidermal tissue
It covers the surface of plants
Strengthening tissue
It provides support for plants
Xylem tissue
It transport water and mineral salts




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