Robert Hooke first observed cells in 1665 using a primitive microscope. The cell theory proposed by Schleiden and Schwann states that all living things are made of cells, cells are the basic unit of structure and function, and new cells are produced from existing cells. Organisms can be either unicellular, consisting of a single cell, or multicellular, consisting of many cells. The basic features of cells include a plasma membrane that regulates what enters and exits the cell, cytoplasm within the membrane, and a nucleus containing DNA.

1. FUNDAMENTAL UNIT OF
LIFE-I
CHAPTER-5

2. INTRODUCTION

3. INTRODUCTION
 What are the organisms that we see around us are made up of ?
 We know that there are different types of organisms that are made up of tissues which join
to form organ and organ system. There are some organisms that are even simpler and do
not contain organ system or organs or even tissues.
 However all organisms are made up of simpler units called as CELLS.
What are cells ?
 The cell is the basic structural and functional unit of all living organisms.
 It is the smallest part of the body of an organism which is capable of independent existence and is able to
perform all the essential functions of life.

4. BRIEF HISTORY OF THE CELL
 Cells were first discovered by Robert
Hooke in 1665. He observed the
cells in a cork slice with the help of a
primitive microscope.
 Cork is a substance which comes
from the bark of a tree.
 Robert Hooke saw that the cork
resembled the structure of a
honeycomb consisting of many little
compartments. Robert Hooke called
these boxes cells.
 Cell is a Latin word for ‘a little
room’.
Cork
Simple
Microscope

5. OTHERS WHO CONTRIBUTED
 Leeuwenhoek (1674), with the improved microscope,
discovered the free living cells in pond water for the first
time.
 Purkinje in 1839 coined the term ‘protoplasm’ for the
fluid substance of the cell.

6. CELL THEORY
Matthias Schleiden
Concluded that all
plants are made of cells
(1838)
Theodore Schwann
Concluded that all
animals are made of
cells (1839)
Rudolf Virchow
Concluded that all cells
-came from pre-existing
cells (1855)
CELL THEORY
 All living things are made up of cells.
 Cells are the basic units of structure and function in an organism
 New cells are produced from existing / pre-existing cells.
(Note :- We now know that cells divide to produce new cell via cell
division called as ‘Mitosis”)

7. CELL

8. COMPOUND MICROSCOPE

9. HOW DO CELLS LOOK LIKE UNDER
MICROSCOPE
SECTION OF ONION PEEL MOUNTED ON A
MICROSCOPE
SECTION OF HUMAN CHEEK CELLS
MOUNTED ON A MICROSCOPE

11. FEATURES OBSERVED UNDER THE
MICROSCOPE

12. DIFFERENCE BETWEEN PLANT CELL
& ANIMAL CELL

13. PLANT CELL VS ANIMAL CELL

14. HOW TO DRAW

15. ARE ALL ORGANISMS ALIKE
 Different organisms are made up of different types of cells.
 Ex :- A plant cell is different that the cells found in
animals.
 The body of an organism can be made up of
 a single cell (cellular level of organisation, Ex:- Amoeba) or
 many cells combine to form tissues (tissue level of organisation),
 tissues inturn combine to form Organs and Organsystem.
 Based on this the organisms are classified as
 Unicellular organism
 Multicellular organism

16. DIFFERENCE BETWEEN UNICELLULAR &
MULTICELLULAR ORGANISM

17. UNICELLULAR ORGANISM
Amoeba
Algae
Paramecium
Chlamydomonas
Euglena
Volvox
A single cell is
capable of
performing all the
essential life
process required
for the survival of
the organism

18. MULTICELLULAR ORGANISMS
 Are Multicellular organisms made up of same type of cells ?
The body of multicellular organisms are made up of
different type of cells.
Ex:- Human beings
 Human Brain consist of Neurons/Nerve cells
which are completely different than any other cell
in the body.
 Similar Smooth muscle cells are different and
perform different function compared to
Neuron/Nerve cell or another other cell in the
body.
(Note :- RBC’s are the only non-nucleated cells
found in the human body.)

19. BASIC STRUCTURE OF CELL

20. WHAT ARE THE CELLS MADE UP OF

21. CELL/PLASMA MEMBRANE

22. CELL MEMBRANE/PLASMA MEMBRANE
 Plasma membrane is a semi-permeable membrane.
 It is composed of lipids and proteins.
 It is the outermost covering of the cell that separates the contents of the cell from
the external environment.
 The plasma membrane allows the entry and exit of some materials in and out of the
cell.
 It also prevents the movement of some other materials, hence the cell
membrane/plasma membrane is also called selectively permeable membrane.

23. CELL MEMBRANE/PLASMA MEMBRANE
Plasma membrane or Cell membrane is made up of lipids & proteins

24. FUNCTIONS OF PLASMA MEMBRANE
 Plasma membrane selectively regulates the entry and exit of
the substances into and out of the cell. Therefore, it is
called selectively permeable 0r semi-permeable membrane.
 It provides an outer boundary to the cell and protects the
cell from injury.
 It allows the flow of materials and information between
different organelles of the same cell, as well as between the
adjacent cells.
 It provides some organic connections between the adjacent
cells.

25. MOVEMENT OF MOLECULES ACROSS
THE CELL/PLASMA MEMBRANE
MOVEMENT OF PARTICLES ACROSS THE MEMBRANE
DIFFUSION HELPS IN THE MOVEMENT
OF MOLECULES SUCH AS CO2 OR O2
ACROSS THE MEMBRANE

26. PHYSIOLOGICAL PROCESS

29. DIFFERENT TYPE OF SOLUTIONS
BASED ON SOLUTE CONCENTRATION

30. EFFECT OF DIFFERENT TYPE OF
SOLUTION ON ANIMAL CELL & PLANT
CELL

31. TYPES OF OSMOSIS

32. ENDOSMOSIS VS EXOSMOSIS

33. CELL WALL

34. CELL WALL
 Cell wall is present only in Plant cell.
 It is a rigid protective covering outside the cell membrane.
 Presence of cell wall distinguishes them from animal cells.
 Most of the cell wall is made up of cellulose.
 Functions
Cell wall gives definite shape to the plant cell
It provides mechanical strength to the cell.
It protects the protoplasm against mechanical injury.
It gives rigidity to the cell.

35. PLASMODESMATA
Cytoplasmic connections between
adjacent plants cells that form a
continuous channel.
Function :
 Enables transport of proteins,
ions & minerals
 Transport of chemicals.

36. PLASMOLYSIS
 Shrinkage of cell due to water loss.
 Happens when a cell is submerged in a hypertonic solution.

37. SUMMARY

38. SUMMARY
 Cell was first discovered by Robert Hooke.
 Schleiden & Schwann proposed the “Cell theory”, according to which all plants and animals are
made up of cells, cell is the basic structural and functional unit of an organism, and all cells arise
from pre-existing cells.
 Organism are classified as
Unicellular &
Multicellular
 Certain physiological process such as
Diffusion
Osmosis
Active & Passive transport
help in the movement of molecules across the plasma membrane
 Basic structure of cell comprises of
Cell membrane/Plasma membrane
Nucleus
Cytoplasm

39. THANK YOU