Cell structure and functions of cell organelles with appropriate pictures on the basis of CDC syllabus for Grade-8 science

1. Living Beings and their
Structures

2. The Cell

3. Discovery of the cell:
• Robert Hooke in 1665,
observed thin slice of
cork under self built
microscope.
• Partitioned boxes or compartments in the slice
• Like a honeycomb
• Hooked coined the term ‘cell’ for each box
derived from Latin word ‘cella’ which means
small room.

4. Cell Theory
• Basic structural units; All living things are made up
of cells.
• Cells are the smallest working units of all living
things.
• All cells come from pre-existing cells through cell
division.
• Millions of living organisms of
different shape and sizes.

5. Definition of Cell
The basic structural and functional unit of life
is known as cell.
Why is cell known as basic structural and
functional unit of life?
• The function of an organism as a whole is
the outcome of combined activities and
interactions of the constituent cells.

6. Examples of Cells
Amoeba proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria

7. Types of Cells
•Prokaryotic cell (size 0.2-2.0 micrometer)
•Eukaryotic cell (size 10-100 micrometer)
On the basis of nuclear organization,
are of two types:

8. Prokaryotic
(pro = primitive and karyon = nucleus
i.e. primitive nucleus)
• Do not consists true
nucleus
• Do not have membrane
bound organelles such
as mitochondria,
endoplasmic reticulum
etc.
• Few internal structures
• One-celled organisms,
Bacteria

9. Eukaryotic
(eu = true and karyon = nucleus i.e. true nucleus)
• Have true nucleus
(DNA and RNA)
• These cells have
membrane bound
organelles
• Present in most living
organisms
Plant cell
Animal cell

10. “Typical” Animal Cell

11. “Typical” Plant Cell

12. Different Parts of Cell
Cell Organelles

13. Cell wall
Cell membrane
Cytoplasm
Nucleus
Mitochondria
Golgi complex
Endoplasmic Reticulum
Ribosomes
Lysosomes
Vaculoe
Plastid

14. Cell Wall
• Most commonly found
in plant cells (cellulose)
& bacteria (chitin)
• Supports & protects
cells and maintains
rigidity
• Exhibits filtering
mechanism

15. Cell Membrane (Plasma membrane)
• Outer membrane of animal cell
• Made up of lipid and protein
molecules
• Allows entry of useful
materials and exit of unwanted
materials
• Provide shape to animal cell
• Holds cytoplasm and
organelles, and protects from
external injury
 Why it is known as semi-permeable membrane?

16. Cytoplasm (Protoplasm)
• Gel-like mixture (organic and inorganic
materials like; water, minerals, salts, proteins
etc.)
• Helps in intracellular distribution of materials
• Surrounded by cell membrane
• Holds sub-cellular organelles
• Contains hereditary material (prokaryotic cell)

17. Nucleus
• Directs cell activities
• Separated from cytoplasm by nuclear
membrane
• Contains genetic material – DNA
• Helps in cell division and hence in
reproduction
Why nucleus is known as brain or director of
the cell?

18. Nuclear Membrane
• Surrounds nucleus
• Made of two layers
• Openings allow material
to enter and leave
nucleus

19. Nucleoplasm
• Transparent semi-fluid substance
• Contains nucleolus, chromatin network and
various enzymes
• maintain the shape and structure of the nucleus

20. Nucleolus
• Inside nucleus, dense
and round structure
attached to chromatin
fiber
• Contains RNA to build
proteins

21. Chromatin fiber (chromosome)
• Contains hereditary
information
• Made of DNA
• Contain instructions for
traits & characteristics
• 23 pairs of
chromosomes are found
in human being

22. Mitochondria
• Produces energy through chemical
reactions – breaking down fats &
carbohydrates
• Controls level of water and other
materials in cell
• Recycles and decomposes proteins,
fats, and carbohydrates
• Holds genetic material, DNA
called mitochondrial DNAs
• Stores energy in the form of ATP
(adenosine triphosphate)
Why mitochondraiis known as powerhouse of the cell?

23. Golgi Bodies
• Golgi complex, Golgi
apparatus or Golgi
• Protein 'packaging plant‘
(process, package and store
macromolecules synthesized
by the cell)
• Helps in the synthesis of
hormones, glycoproteins etc.
• Move materials out of the cell
• Responsible for synthesis of
cell wall, cell membrane and
lysosomes

24. Endoplasmic Reticulum
• Helps in the synthesis of
proteins, fats and lipids
• Moves materials around within
a cell, acts as a pathway
• Supports framework of the cell
• Smooth type: lacks ribosomes
• Rough type (pictured):
ribosomes embedded in
surface

25. Ribosomes
• Each cell contains thousands
• Found on endoplasmic
reticulum or floating freely
throughout the cell
• Made up of complexes
RNAs and proteins
(ribonucleoprotein complex)
• Responsible for synthesis of
proteins

26. Lysosome
• Hydrolytic enzymes (digestive
enzymes), proteins, fats, and
carbohydrates
• More than 60 enzymes,
(protein or food digestion)
• Transports undigested material
to cell membrane for removal
• If lysosome explodes ,
digestive enzymes starts to
digest own cell
• Why it is called suicidal bag?

27. Vacuoles
• Membrane-bound sacs
for storage, digestion,
and waste removal
• Contains water solution
• Help plants maintain
shape

28. Plastids
On the basis of pigments
found on plastids, they are
of three types:
• Chloroplast (kithcen of
the cell)
• Chromoplast
(Colourful)
• Leucoplast (colourless)

29. Chloroplast
• Usually found in plant
cells
• Contains green
chlorophyll
• Where photosynthesis
takes place