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Cellstructure
• Presented by
• Lahange Anil Trimbak
• Borse Shaila Bhausaheb
Guide
Prof. Desale S. Y.
Introduction to cell
 It was Robert hook who In 1665 first discovered these
building blocks when he observed a thin slice of cork under
his self designed microscope.
 These compartments of cork were empty.
 He found they resembled the structure of honey comb and
labeled them, as ‘cell’ which in Latin means ‘small rooms’.
 Every living things , however different, is made up of these
separate tiny units called ‘cells’ .
Morphology of cells
 Size of cells varies greatly [0.1µm to 18cm] in diameter.
 The unit used to measure size of a cell is micrometer[µm]
 1 micrometer = 1/1000 millimeter.
 Small size of cell ensures greater surface area . Greater
surface area ensures greater diffusion of nutrients into the
cell ,greater extent of exchange of materials in &out of the
cell ,also easy repair of the damaged cell.
 Smallest cell – cells of Mycoplasma galliseptium (0.1µm)
 Largest cell – egg of an ostrich (18cm) in diameter .
Cell structure
Parts of a Cell
1.Plasma membrane
2 .Cell wall [in plant cell].
3.Cytoplasm
4.Cell organelles
Plasma membrane
 As a cell is a distinct unit of life ,every cell is bound by a thin
covering which separates the contents of the cell from its
external environment & gives separate identity to the cell
this covering is called plasma membrane.
 It is a living, extremely delicate elastic membrane of about
70A0 thickness (1A0=10µm =107 mm).
 It made up of a lipid bilayer having integrated protein
molecule .
 The organization of the plasma membrane is not fixed &
hence it is flexible.
Cell wall
 In addition to plasma membrane ,plant cell have another
rigid outer covering called the cell wall .
 The cell wall is non living &freely permeable .
 It is made up of cellulose.
 It gives protection to the cell & also determines its shape .
Cytoplasm
 The fluid which lies in between the plasma membrane &
nucleus is called cytoplasm.
 Living cytoplasm is constantly moving .
 It is jelly- like substance.
 Many cell organelles lie in the cytoplasm .
 Cellular chemical reactions take place in the cytoplasm
 The part of cytoplasm other than organelles is called
cytosol.
 It stores vital substance like amino acids ,glucose ,vitamins
etc.
Cell organelles





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Nucleus
Endoplasmic reticulum
Golgi Apparatus
Lysosomes
Mitochondria
Plastids
Vacuoles
Nucleus
 Nucleus is a large spherical body generally lying at the Centre
of a cell .
 It is the most important part of the cell .
 Nucleus covered by a double layered nuclear membrane .
 The nuclear membrane has pores
• Functions
i.
It controls all metabolic activities of the cell . If it is
removed ,the cell ultimately dies.
ii. It play an important role in cell division
iii. It is involved in transmission of hereditary characters from
Parents to offspring.
Endoplasmic reticulum
 Endoplasmic reticulum is a large network of membrane bound
,fluid filled inter connecting tubules & sheets.
 ER spreads from the nuclear membrane to the plasma
membrane.
 Endoplasmic reticulum is of two type
-Rough endoplasmic reticulum (RER)
- Smooth endoplasmic reticulum (SER)
Functions of ER:
i.
Along with intracellular transport it also acts as a supportive
framework for a cell
ii. It synthesize proteins &lipids and transports them. Some lipids
synthesized by it are used in building plasma membrane while
some other lipids and proteins are used as hormones and
enzymes
iii. It transports proteins synthesized by
ribosomes.
iv. SER of certain cells of liver play a crucial role
in detoxification many poisons and drugs
which enter our body through food ,air or water.
Golgi Apparatus
 Golgi apparatus was first described by a German scientist
“Camillo Golgi ’’.
 It comprises of five to eight (sometime more ) sacs which
resemble deflated balloons placed approximately parallel
to each other .
 These sacs are called cisternae and filled with different
enzymes.
• Functions
Golgi complex is the secretory organ of the cell .
It modifies , sorts and packs materials synthesized in the
cell ( enzymes mucous secretion , proteins ,lipids
,pigments etc.) .&dispatches them to various targets
inside the cell or outside the cell.
iii. It produce vacuoles & secretory vesicles.
iv. It plays the role in formation of the cell wall , plasma
membrane & lysosome.
i.
ii.
Lysosomes
 Lysosomes are simple one membrane bound sacs ,filled with
digestive enzymes.
 These powerful enzymes are made by RER and are capable of
digesting and breaking down all organic matter .
 It is the cell’s waste disposal system .
• Functionsi.
As it is the digestive system of the cell ,it protect the cell by
destroying any foreign material like bacteria &viruses that invade
the cell.
ii. They remove worn out cellular organelles and remove all the
organic debris . This process is called autolysis .So they are called
as ‘Demolition Squads’.
iii. When a cell gets old or it damaged ,lysosome burst and the
enzyme digest their own cells .therefore lysosomes are also
Mitochondria
 It is also known as power house of the cell because it
produce energy for the cell.
 It is double membrane structure .
 The outer membrane is porous while the inner membrane
is deeply folded .
 These folds are called cristae .
 The interior cavity is filled with proteinaceous gel like
matrix which contains ribosomes ,phosphate, granules
&DNA.
 Mitochondria oxidize carbohydrates &fats present in the
cells with the help of enzymes .
• Functions
i.
ii.
Mitochondria produce the energy rich compound ATP
which is the energy
currency of the cell.
The body uses the energy stored in ATP to synthesize
chemical compounds
and to do mechanical work.
Plastids
 Plastids are double membrane structures present only in
plant cells .
 They are of two types :- Chromoplasts
Leucoplast
 Chloroplast are a type of chromoplasts which are green in
color due to the presence of green colored pigment called
chlorophyll.
Functions
i.
Chloroplasts helps to harness solar energy and convert it
into chemical energy in the form of food
ii. Chromoplasts give color to flowers and fruits.
iii. Leucoplasts are involved in the synthesis and storage of
various kinds of food like starch ,oil &proteins.
Vacuoles
 Vacuole are storage sacs for solid or liquid contents .
 They do not have any shape or size.
 The structure of the vacuole changes according to the need
of the cell.
 Vacuole is bound by a single membrane.
• Functions
i.
ii.
Vacuole help to maintain osmotic pressure of the cell .
They store metabolic byproducts and end products e.g.
Glycogen, protein &water
iii. They stores waste products and food in animal cell .
iv. In plant cells vacuoles are full of cell sap and provide
turgidity and rigidity to them.
Difference between Plant cell
&animal cell
Plant cell
i. It contains chloroplast
ii. Plant cell larger than animal
cell
iii. Centrioles absents
iv. Large vacuoles are present
Animal cell
i. It does not contains
chloroplast
ii. Animal cells are smaller
than plant cell
iii Centrioles preset
iv Few small sized and
temporary vacuoles are
present
Difference between prokaryotic &
eukaryotic cell
Eukaryotic cells
i. In Greek ; Eue =true
Karyone =nut ,kernel
ii. They have well defined
nucleus i.e. with nuclear
membrane , nucleus &
nucleoplasm.
iii. Size of eukaryotic cells
ranges from 5-100 µm.
Iv. They have more than one
chromosome.
Prokaryotic cells
i. In Greek ; Pro = before
Karyone= nut , kernel
ii. Their nucleus lacks nuclear
membrane
iii. Prokaryotic cells are smaller
in size ranging from 1-10 µm
Iv. They contain a single
chromosome.
Eukaryotic cells
Prokaryotic cells
V. Mitochondria are present.
Vi. E.g. higher advanced
unicellular and multicellular
plants & animals
V. Mitochondria are absent.
Vi. E.g. Blue green algae