The document discusses cells and cell theory. [1] Robert Hooke first observed cells in 1664 while examining cork under a microscope and coined the term. [2] Matthias Schleiden and Theodor Schwann later proposed cell theory, which states that all organisms are made of one or more cells and cells only arise from pre-existing cells. [3] Cells exist in various shapes and sizes depending on their function, and can be observed under a microscope.

1. By Leonardo k Goes

2. In our day to day life, we come across several
things. Have you ever wondered what each of
these things is made up of ? You may
observed that some things appear to be made
of similar repetitive unite. The respective units
are called “building block" of these things

3. Robert Hooke (1635-1703) an
Englishman, first discovered the cell in
1664 while examining a slice of cork
under a microscope. Hook observed
that a slice of cork is made up of tiny
honeycomb-like
compartments, arranged one on top of
the other. He called these
compartments ‘cells’ . It was much later
that scientists discovered that living
things are made up of cels.

5. Today biologists study living things based on cell
theory proposed by tow German
scientists, Matthias Schleiden and Theodor
Schwann. The
cell theory states that
1) All organisms are made of one or more cells
2) Cells arise from pre-existing cells
You may be amazed to know that irrespective of
number of cells an organism is made up of, cell
theory applies to every organism in the world.

6. Organisms that consist of many cell are called
unicellular organisms. Examples are amoeba,
Paramoecium, Euglena.

7. Organisms whose body consist of many cell are
called multicellular organisms. Examples are plants
animals and human beings

8. Cells exist in different shapes. They can be disc-
shaped, polygonal, rectangular, branched, or even
irregular. The shape of a cell depends on the on
the specific function it performs.
Most cells are microscopic and cannot be seen
with a naked eye. Cell size may vary from
micrometer to a few centimeters. The generally
range in size from 0.1 to 0.5 micrometers. The
Largest cell is the egg of an ostrich 170 millimeter
in diameter.

9. Most cells can viewed with the help of a compound
microscope. The object to be viewed
under the microscope is generally referred to as
to the specimen. A thin glass sheet of glass called
called a microscopic slide which is used to hold a
sample of the specimen. A second much thinner,
sheet of glass called cover slip.
Purpose of cover slip:-
1) It protects the microscope’s objective lens by
preventing it from coming into contact with the
specimen sample.
2) It helps to create an even thinness for the sample.

11. Through cell may differ in shape size, all of them
have the same basic structure, referred to as the
generalized cell structure or generalized cell. The
cell has both living and non living parts. The
living parts of a cell that have a definite shape
function are called organelles.

12. 1) Cell membrane
2) Cytoplasm
3) Nucleus
4) Golgi apparatus
5) Vacuole
6) Lysosome
7) Endoplasmic reticulum
8) Ribosome
9) Centrosome
10) Plastid
11) Mitochondria (power house of the cell)

13. Although plants and animals cell have the same
structure, there are certain differences between
them. We are going to discuss this in the next
slide.

14. PLANTS CELL ANIMALS CELL
 Cell wall is present  Cell wall is absent.
 Cytoplasm is not as  Cytoplasm is dense
dense as in an animal  Vacuole is generally
cell. absent. If present small
 A large vacuole is in size.
present.  Plastid are absent.
 Plastids are usually  Centrosome is present.
present.
 Centrosome is absent.

15. Leonardo Goes