Robert Hooke first observed cells in thin slices of cork in 1665 under his microscope and coined the term "cell" to describe their box-like compartments. The cell theory, proposed by Schleiden and Schwann and elaborated by Virchow, states that the cell is the basic unit of life, all living things are composed of one or more cells, and new cells arise from preexisting cells. Cells come in various shapes and sizes depending on their function, with the smallest being bacteria and the largest being ostrich eggs. Cells are either prokaryotic, lacking membrane-bound organelles and a nucleus, as in bacteria, or eukaryotic, with a nucleus surrounded by organelles, as in plants

1. THE
FUNDAMENTAL
UNIT OF LIFE
BY : MISS RITIMA (TGT –
SCIENCE)

2. INTRODUCTION
 ROBERT HOOKE WHILE EXAMINING
THIN CORK OBSERVED THAT THE
CELLS IN CORCK RESEMBLES THE
STRUCTURE OF HONEY COMB
CONSISTING OF MANY LITTLE
COMPARTMENTS.
 IN YEAR 1665 ROBERT HOOKE GET
CHANCE TO OBSERVE THESE CORCK
CELLS THROUGH SELF DESIGNSED
MICROSCOPE . HE CALLED THESE
BOXES CELL.

3. CORK CELL AS DISCOVERED BY ROBERT HOOKE UNDER
HIS MICROSCOPE.

4. CELL THEORY
PROPOSED BY SCHLEIDEN AND
SACHWANN AND FURTHER
ELABORATED BY VIRCHOW.
POSTULATES
 CELL IS THE BASIC UNIT OF LIFE.
 ALL LIVING ORGANISMS ARE MADE UP
OF CELLS.
 NEW CELLS ARISES FROM PRE-
EXISTING CELLS.

5. SHAPE AND SIZE OF CELL
 THE SHAPE OF THE CELL DEPENDS
UPON THE FUNCTION THEY PERFORM.
 SMALLEST CELL -- PPLO
 LARGEST CEL – OSTRICH EGG
 LONGEST CELL -- NERVE CELL

6. DIFFERENT SHAPES AND SIZES OF CELLS FROM HUMAN
BODY

7. STRUCTURAL ORGANISATION OF CELL
 CELL MEMBRANE
 CELL WALL
 NUCLEUS
 CYTOPLASM
 ENDOPLAMIC RETICULUM
 GOLGI APPRATUS
 PLASTIDS
 VACUOLES

8. STRUCTRE OF CELL

9. PROKARYOTIC CELL AND EUKAYOTIC CELL
PROKARYOTIC CELL EUKARYOTIC CELL
 SIZE IS GENERALLY
SMALL.
 NUCLEUS IS ABSENT.
 SINGLE PRO
CHROMOSOME IS
PRESENT.
 MEMBRANE BOUND
ORGANELLES ABSENT.
 70s RIBOSOMES ARE
PRESENT.
 EXAMPLES: BACTERIA ,
CYNOBACTERIA
 SIZE IS GENERALLY
LARGE.
 NUCLEUS IS PRESENT.
 MORE THAN ONE
CHROMOSOMES.
 MEMBRANE BOUND
ORGANELLES PRESENT.
 80s RIBOSOMES ARE
PRESENT.
 EXAMPLES : PLANTS ,
ANIMALS , FUNGI ,
PROTISTS.

11. FEW IMPORTANT QUESTIONS:
Q1: Who discovered cell?
Q2: State cell theory.
Q3: Name smallest cell.
Q4: Differentiate between plant cell and animal
cell.
Q5: Draw labelled diagram of cell.