Fundamental unit of life- Cell, Cell organelles and their role

Presentation on Fundanetal Unit of Life - Cell

1. A TOUR OF THE CELL
THE FUNDAMENTAL UNIT OF LIFE

2. EXTENT OF TOPIC
What is Cell made up of?
Plasma membrane or Cell membrane
Nucleus and its structure
Cytoplasm and its function
Cell organelles and their functions

3. CELL MEMBRANE OR PLASMA
MEMBRANE
It is the outermost covering of
the cell that separates the
contents of the cell from the
external environment.

 Allows the entry and exit of
materials in and out of the
cell.It also prevents the
movement of some other
material and is therefore called
a selectively permeable
membrane.

The plasma membrane is
flexible and is made up of
organic molecules like proteins
and lipids.

4. Plasma membrane is called a selectively
permeable membrane. Why?
Plasma membrane is called a selectively
permeable membrane because it allows
some materials to enter and leave the cell.

5. DIFFUSION
▶ Gaseous exchange takes place from a region of
high
concentration to a region of low concentration.
▶ For example: Exchange of respiratory gases i.e.
carbon dioxide and oxygen between cell and its
external environment.

6. SOME APPLICATIONS OF DIFFUSION IN
OUR DAILY LIFE
Diffusion in Drop of
Ink



Inhalation of O2 and
Exhalation of CO2
during Breathing


Burning of
Incense Stick

7. OSMOSIS
The movement of water from a
region of high
concentration through a
water
semi-
permeable membrane to a region
of low water concentration.

8. SOME APPLICATIONS OF OSMOSIS
IN OUR DAILY LIFE
Skin of fingers
shrink after
washing
clothes

Plants absorb
water from soil
with the help of
root hairs by
osmosis
Raisin swells up
when soaked in
water

9. DIFFERENCE BETWEEN OSMOSIS
AND DIFFUSION
S.
No.
Diffusion Osmosis
1 It is movement of
molecules or particles.
It is movement of water
molecules.
2 It does not require a
semi - permeable
membrane.
It requires a semi-
permeable membrane.
3 It can occur in any
medium
It occurs only in a liquid
medium.

10. WHAT IS A HYPOTONIC SOLUTION?
Hypotonic solution is the solution
concentration
surrounding the cell which has
than higher water
that in the cell.
Water molecules are free to pass
across the cell membrane in both
directions, but more water will
come into the cell than will leave.
The net result is that the water
enters the cell and the cell is likely
to swell up.

11. HYPOTONIC SOLUTION

12. WHEN IS A SOLUTION SAID TO
BE ISOTONIC?
• When the medium surrounding a cell has the same
concentration of water as that in the cell it is said to
be isotonic.
•Water crosses the cell membrane in both the
directions, but the amount going in is the same as
the amount going out, so there is no overall
movement of water. The cell will stay the same size.

13. ISOTONIC SOLUTION

14. WHAT IS A HYPERTONIC SOLUTION?
When the medium surrounding a cell
has lower concentration of water than
that in the cell it is said to be
hypertonic.

Water crosses the membrane in both
the directions, but this time more water
leaves the cell than enters it. Therefore
the cell will shrink.

15. HYPERTONIC SOLUTION

17. WHAT IS PLASMOLYSIS?
Plasmolysis is the phenomenon by which
a plant cell shrinks away from the cell
wall when it loses water by osmosis.

18. WHAT IS ENDOCYTOSIS?
Endocytosis is the process by which a
cell is able to engulf food and other
material from its external environment
due to the flexibility of the plasma
membrane.

Example : Amoeba acquires its food
through such processes.

19. ENDOCYTOSIS

20. CELL WALL
▶ Hard outer covering of the cell.
▶ Present outside the cell
membrane.
▶ Cell wall is composed of
cellulose.
▶ Cellulose
substance
is a
and
complex
provides
structural strength to plants.
▶ Cell wall is present in the plant
cell and helps the plant to
withstand the environmental
changes.

21. NUCLEUS
 Has a double layered covering called
nuclear membrane.
 Nuclear membrane has pores which
allow the transfer of material from inside
the nucleus to its outside (cytoplasm).
 Contains chromosomes which are
visible as rod-shaped structures only
when the cell is about to divide.
 Chromosomes contain information for
inheritance of features from parents to
the next generation in the form of DNA
molecules. (Deoxyribo Nucleic Acid).

22. NUCLEUS
▶ DNA molecules contain information necessary
for
constructing and organising cells.
▶ Functional segments of DNA are called genes.
▶ When the cell is not dividing, DNA is present as a
part of the chromatin material. Chromatin
material is visible as entangled mass of thread
like structures. Whenever the cell is about to
divide , the chromatin material gets organised
into chromosomes.
▶ It helps in determining the way the cell will
develop and what form it will exhibit on maturity
by directing the chemical activites of the cell.

23. DIAGRAM OF NUCLEUS

24. CYTOPLASM
▶Cytoplasm consists of an aqueous solution called cytosol.
▶ It contains variety of cell organelles and also the waste and
storage products such as starch and glycogen.
▶The cytoplasm occurs between the plasma membrane and
nuclear membrane.
▶The inner part of cytoplasm is called endoplasm and the outer
part is known as ectoplasm. Endoplasm contains granules
whereas ectoplasm contains clear solution.
▶Functions of Cytoplasm:
▶It acts as a store house of various chemicals such as amino
acids, glucose and vitamins.
▶Certain metabolic reactions such as glycolysis takes place
within the cytoplasm.

25. CELL ORGANELLES
1)Endoplasmic
reticulum
2)Ribosomes
3)Golgi apparatus
4)Lysosomes
5)Mitochondria
6)Plastids
7)Vacuoles

26. CELL ORGANELLES FOUND IN CYTOPLASM
Double membrane- bound
organelles
●Mitochondria
●Plastids
Single membrane-bound
organelles
●Endoplasmic Reticulum
●Golgi Apparatus
●Lysosomes
●Vacuoles
Organelles without
membrane
●Ribosomes

27. ENDOPLASMIC RETICULUM
▶ ER is a large network of membrane bound tubes and
sheets or channels bounded by membranes.
▶ Extends throughout cytoplasm of all eukaryotic cells.
▶ ER is absent in prokaryotic cells and mammalian RBCs.
▶ Two types - Rough Endoplasmic Reticulum (RER)
Smooth Endoplasmic Reticulum (SER)
▶ Serves as channels for the transport of materials
between various regions of the cytoplasm or between
the cytoplasm and the nucleus.
▶ Functions as a cytoplasmic framework providing a
surface for biochemical activities.

28. RER
▶ Arranged into flattened sacs.
▶ Ribosomes on surface give it a
rough appearance.
▶ Ribosomes are the sites of protein
synthesis.
▶ Cells that specialize in secreting
proteins have lots of rough ER.

29. SER
▶ A series of interconnected
tubules .
▶ No ribosomes on surface.
▶ Helps in the manufacture
of fat molecules or lipids.
▶ In liver cells of
vertebrates, SER
detoxifies many poisons
and drugs.

30. MEMBRANE BIOGENESIS
▶ It is the process of formation
of the cell membrane from
proteins and lipids
synthesized by endoplasmic
reticulum.

31. RIBOSOMES
▶ They are smallest and spherical organelles and not
bound by membrane.
▶ They either occur scattered in the cytoplasm or
attached to the surface of endoplasmic reticulum
forming rough endoplasmic reticulum.
▶ They are formed of ribosomal RNA and proteins.
▶ These are sites of protein synthesis, hence called the
protein factory of the cell.

32. GOLGI APPARATUS
First discovered by Camillo Golgi in 1898.
It consist of a system of membrane- bound vesicles
arranged parallel to each other in stacks called
cisterns.
It is present in all eukaryotic cells except RBCs.
It has a convex cis face and a concave trans face.
Cis face receives vesicles from ER, join to form new
cisternae of Golgi.
Secretory vesicles and lysosomes are formed from
the trans face of Golgi complex and is called
maturing face.
The material synthesized near the ER is packaged
and dispatched to various targets inside and outside
the cell through the Golgi apparatus.
Its functions include storage , modification and
packaging of products in vesicles.
Synthesis of complex sugar from simple sugar.
Involved in the formation of the lysosome.

34. LYSOSOMES
Waste disposal system of the
cell.
Found only in animal cells.
Keep the cell clean by digesting
any foreign material as well as
worn out cell organelles.
Contain powerful digestive
enzymes capable of breaking
down all organic material.
When the cell gets damaged,
lysosomes may break open and
the enzymes digest their own
cell. Thus known as suicide bags
of a cell.

35. MITOCHONDRIA
Known as the powerhouse of the cell.
The energy required for various chemical activities is released by
the mitochondria in the form of ATP molecules. ( Adenosine
triphosphate).
On the cristae they have F0-F1 particles which helps in generation
of energy in the form of ATP.
ATP is known as the energy currency of the cell.
Mitochondria have two membrane coverings.
Outer membrane is very porous.
Inner membrane is deeply folded.
Mitochondria are able to make their own proteins as they have their
own DNA and ribosomes and are called semi-autonomous organelle

36. PLASTIDS- THE KITCHEN OF THE CELL
Present in plant cells only.
Three types- 1) Chromoplasts (coloured)
2)Chloroplast (coloured)
3)Leucoplasts (colourless)
▶ Chromoplasts contain yellow, orange and red pigments. They are
mostly found in flowers and fruits.
▶ Plastids containing green pigment chlorophyll are called
Chloroplasts.
▶ Leucoplasts are colourless plastids without any pigment. They are
located in non-photosynthetic tissues of plant such as roots, bulbs
and seeds.
▶ Leucoplasts store materials as starch, oils and protein granules.
▶ Plastids contain membrane layers embedded in a material called
stroma and a membranous system called granum/grana and joined
by structure called lamellae/lamella.
▶ Each granum consists of a stack of membrane-bound sacs, called
Thylakoids. They help in trapping solar energy.
▶ Chloroplast contains its own DNA, RNA and ribosomes and can
synthesize their own proteins because of which they are also known
as semi-autonomous organelle.

37. CHLOROPLASTS

38. VACUOLES
▶ Storage sac for solid or liquid contents.
▶ Small size vacuoles are present in animals.
▶ Large in plants.
▶ In plant cells, vacuoles are full of cell sap and
provide turgidity and rigidity to the cell.
▶ Vacuoles store amino acids, sugars, various
organic acids and some proteins.
▶ Contractile vacuoles helps in maintaining the
water balance and in excretion.
▶ Sap vacuoles maintain osmotic concentration in
plant cells needed for water absorption.

40. Overview of a plant cell

41. Overview of an animal cell