Cell The unit of life

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This is in collaboration with CBSE NCERT Class 11th biology..

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CELL : THE UNIT OF LIFE

RIBOSOMES :

RIBOSOMES Ribosome was first observed by George Palade. They are composed of RNA and proteins are not surrounded by any membrane. The eukaryotic ribosomes are 80S while prokaryotic are 70S. [here ‘S’(Svedberg’s unit].

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RIBOSOME

CYTOSKELETON :

CYTOSKELETON It is an elaborate network of filamentous proteinaceous structures present in cytoplasm. Functions: Mechanical support , motility, maintenance of the shape of the cell.

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CYTOSKELETON

CILIA AND FLAGELLA:

They are hair like outgrowths of the cell membrane. Cilia are small structures which works like oars causing the movement of either the cell or the surrounding fluid . Flagella are comparatively longer and responsible for cell movement. Studies show that they are covered with plasma membrane Their core called axoneme , possesses a no. of micro tubes running parallel to the long axis. Both emerge from centriole like structure called Basal bodies. CILIA AND FLAGELLA

CILIA AND FLAGELLA:

CILIA AND FLAGELLA

CENTROSOMES AND CENTRIOLES :

CENTROSOMES AND CENTRIOLES Centrosome is an organelle usually containing 2 cylindrical structures called centrioles . They are surrounded by amorphous pericentriolar materials. The central part of the proximal region of the centriole is also called the hub. The centriole form the base body of cilia or flagella, and spindle fibers that give rise to spindle apparatus during cell division in animal cells.

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CENTROSOMES AND CENTRIOLES

NUCLEUS:

NUCLEUS It was first described by Robert Browning 1831. The material of the nucleus stained by the basic dyes was given the name Chromatin by Flemming . The interphase nucleus has higly extended and elaborate nucleoprotein fibres called Chromatin, nuclear matrix and one or more spherical bodies called Nucleoli. Perinuclear space forms a barrier between the materials present inside the nucleus and that of cytoplasm. The nuclear matrix or the cytoplasm contains nucleolus and chromatin. Chromatin contains DNA and some basic proteins called histones .

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NUCLEUS

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NUCLEUS

CHROMOSOMES:

CHROMOSOMES Every chromosome has a primary constriction or the centrosome on the sides of which the disc shape structures called kinetochores . The metacentric chromosome has middle centrosome slightly away from the middle of the chromosome resulting one shorter arm and one longer arm In Acrocentric chromosome, the centrosome is situated closed to its end, forming one extremely short and one very long arm. The telocentric chromosome has a terminal centrosome . Chromosomes having non-staining secondary constructions at a constant location gives appearance of a small fragments called the Satellite

MICROBODIES:

MICROBODIES Many membrane bound minute vesicles called microbodies that contain various enzymes, are present in both plant and animal cells.

THANKYOU By- Vignesh (vigneshb2009@gmail.com):

THANKYOU By- Vignesh (vigneshb2009@gma i l.com)

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