Cell class 8 presentation

CHAPTER - 8
CELL - STRUCTURE AND FUNCTIONS
CLASS :- VIII
MADE BY :- RAVI PRAKASH SINGH
SUBJECT :- BIOLOGY
Sunday, December 10, 2017RAVI PRAKASH SINGH
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• The cell is the smallest unit of life.
• Cell is basic structural and functional
unit of living organisms.
• New cells arise from pre-existing
cells.
• All organisms are composed one or
more cells.
Sunday, December 10, 2017 RAVI PRAKASH SINGH
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 Robert Hooke was the first scientist to discover
existence of cells with the help of a microscope in
1965.
 He observed thin slices of cork (a part bark of a tree)
under a microscope and saw honeycomb structures.
 The slices of cork appeared like small compartments
which were further separated by a wall.
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 Cell Number:
• On basis of no. of cell, living organisms can be
classified into two categories:-
1) Unicellular- Living organism consist of single cell.
Example- Amoeba, Euglena
2) Multicellular- Living organism consist of more than
one cell. Example- Earthworm, Human being.
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 Cell Shape:
• The shape of cell differ not only in different organisms, but also
in different organs of same organism
• Shape may be oval spherical cuboidal, fibre like or polygonal
 Cell size:
• The difference in size of organism is due to the number of cells
present in them
• The smallest cell PPLO (Plero Pneumonia –like organism) are
called mycoplasma is about 0.1 micron in diameter
• The largest cell is ostrich cell with 170 mm in diameter
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Cell Membrane (plasma membrane)
• Outer membrane of cell that controls
the entry and exit of substances
according to the requirement of cell
the cell.
Cell Wall
• It provide rigidity, Supports & protection to cell.
• It also give shape, size .
• Found in plants, fungi, bacteria.
• Surrounds plasma membrane
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Cytoplasm
• The portion of the protoplasm lying inner to cell
membrane, but outside the nuclear membrane.
• It comprises of Gel-like substances that fills the
inside of the cell.
• Contains hereditary material
Nucleus
• Separated from cytoplasm by nuclear
membrane
• Directs all cell activities.
• Contains genetic material - DNA
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NUCLEAR MEMBRANE
• Surrounds nucleus
• Made of two layers
• Openings allow material to enter
and leave nucleus
• It is made of DNA and present in nucleus
• It is responsible for the inheritance of characters
(genes) from one generation to other
CHROMOSOMES
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Cell Organelles
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The cell organelles are:
• Plastids: Plastid are large organelles &
characteristic of plant cell.
⇒ Chloroplasts: provide green color and
Manufacture food for plant by the process of
photosynthesis
⇒ Chromoplasts: for providing color other than

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Mitochondria
• They are rod shape or spherical
structures.
• Responsible for cellular respiration &
produces energy for different activities.
• So, it is called power house of cell
• Controls level of water and other
materials in cell
• Recycles and decomposes proteins,
fats, and carbohydrates
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Endoplasmic Reticulum
• It is network of membranes.
• It provides a skeletal framework to the
cell.
• Moves materials around in cell.
Ribosomes
• Each cell contains thousands
• Make proteins
• Present in the cytoplasm & float
throughout the cell
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Golgi Complex
• Sac-like structure stacked one above
the other
• Store the material produced by cell
• So they are called store house of the
cell
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Vacuoles
• Empty space in the cytoplasm
• It store excess of water and
Waste product
• In amoeba , it held food for
digestion.
Cilia and flagella
• They are small extensions on their cell membrane
• They help in locomotion & collection of food.
• Paramecium have numerous cilia while Euglena has a
single flagellum.Sunday, December 10, 2017 RAVI PRAKASH SINGH
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• Euglena
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Cells Types
On the basis of their nuclear organization, cells are of types:
 Prokaryotic: In Greek, pro : primitive; karyon : nucleus.
1) No Nucleus
2) No membrane-bound organelles like mitochondria or chloroplasts.
3) Bacteria and Blue-Green algae
4) Reproduce asexually by budding and fission
5) First type of cell on the earth
6) Very small (1 - 10 µm)
 Eukaryotic: In Greek, Eu : True; karyon : nucleus.
1) True Nucleus
2) Membrane bound organelles
3) All other organisms except Bacteria and Blue-Green algae
4) Cell size generally 10 - 100 µm
5) Some are larger
6) Include fungi, protists, plant, and animal cells.
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“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
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http://waynesword.palomar.edu/images/plant3.gif
“Typical” Plant Cell
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Cell Components /
organelles
Plant Cell Animal Cell
Cell wall present Absent
Cell membrane Present Present
Plastid Present Absent
Mitochondria Present present
Nucleus Present present
Vacuoles Large size & more in
number
Small size or Absent
Chloroplast Present Absent
Ribosomes Present Present
Shape Fixed Irregular
Golgi Apparatus Present Present
size Larger Comparatively Smaller
Differences Between Plant and Animal Cells
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Levels of organization of living being
CELL TISSUE ORGAN ORGAN SYSTEM ORGANISM
1) CELL : cell is the smallest unit of life.
2) TISSUE : Group of similar cells that perform specific function.
3) ORGAN : Group of different tissues form an organ. Ex – liver, kidney, stomach
4) ORGAN SYSTEM: Group of organ that work together to perform specific functions. Ex- Digestive
System , circulatory system etc.
5) ORGANISM : Different organ systems work together to form organism.
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Cell Division And cell Growth
Cell Growth :
When a cell is formed it is small but it gradually grow in size by taking nutrients and after
reaching certain size , it divides into two new cells.
Cell Division :
Cell division is the process by which a parent cell divides into two or more daughter cells
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Sunday, December 10, 2017
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RAVI PRAKASH SINGH

Cell class 8 presentation

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