Cell theory

1. Cell Theory
Prepared By: Yatin Sirohi
School Name : The Aaryans
Class : 11th A

2. Objective IN presentation
• History
• What is cell theory
• Proposers of cell theory
• The three tenets of the cell theory
• Modern interpretation

3. History
• With continual improvements made to microscopes over
time, magnification technology advanced enough to discover
cells. This discovery is largely attributed to Robert Hooke.
Robert Hooke's microscope was a recreation of Anton van
Leeuwenhoek's microscope in the 17th century, except his
was 300x magnification. The discovery of the cell was made
possible through the invention of the microscope

4. What is cell theory
•The cell theory states that all biological
organisms are composed of cells; cells are
the unit of life and all life come from
preexisting life. The cell theory is so
established today that it forms one of the
unifying principles of biology.

5. Proposers of cell theory
•The cell was first discovered by Robert Hooke in
1665. One observation was from very thin slices of
bottle cork. Hooke discovered a multitude of tiny
pores that he named "cells“.
•In 1838, Matthias Schleiden, a German botanist,
examined a large number of plants and observed
that all plants are composed of different kinds of
cells which form the tissues of the plant.

6. Proposers of cell theory
• Theodore Schwann (1839), a British Zoologist, studied
different types of animal cells and reported that cells had a
thin outer layer which is today known as the ‘plasma
membrane’. He also concluded, based on his studies on plant
tissues, that the presence of cell wall is a unique character of
the plant cells. On the basis of this, Schwann proposed the
hypothesis that the bodies of animals and plants are
composed of cells and products of cells.

7. Proposers of cell theory
• Schleiden and Schwann together formulated the cell
theory. This theory however, did not explain as to how
new cells were formed. Rudolf Virchow (1855) first
explained that cells divided and new cells are formed
from pre-existing cells (Omnis cellula-e cellula). He
modified the hypothesis of Schleiden and Schwann to
give the cell theory a final shape.

8. The three tenets of the cell theory
1.All living organisms are composed of one or more
cells.
2.The cell is the basic unit of structure and organization
in organisms.
3.Cells arise from pre-existing cells.

9. Modern interpretation
• The generally accepted parts of modern cell theory include:
• All known living things are made up of one or more cells.
• All living cells arise from pre-existing cells by division.
• The cell is the fundamental unit of structure and function in all living organisms.
• The activity of an organism depends on the total activity of independent cells.
• Energy flow (metabolism and biochemistry) occurs within cells.
• Cells contain DNA which is found specifically in the chromosome and RNA found
in the cell nucleus and cytoplasm.
• All cells are basically the same in chemical composition in organisms of similar
species.

10. Thank You