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The Cell Theory
In the early 1600’s
Hans & Zachariah
Jansen constructed
the first light
microscope.
T. Preece 2007.
The Cell Theory
In 1665 Robert
Hooke examined
a piece of cork
with a microscope
to discover “it was
made of tiny boxes”
which he called
cells.
Kevin Quigley. 2006.
The Cell Theory

In 1846, Robert Brown described the
nucleus of the cell
Kevin Quigley. 2006.
Schleiden & Schwann
Kevin Quigley. 2007.
Rudolf Virchow
Kevin Quigley. 2007.
The Cell Theory
These early discoveries (and others that we will soon
look at in more detail) led scientists to develop the
‘cell theory’ which states:
1. All living things are made up of cells.
2. All cells come from pre-existing cells.
3. Cells are the smallest T.units
of life
Preece 2007.
What We Know Now...

Now days, due to great advancements in
technology, we know much more about
cells.
T. Preece 2007.
Light & Electron Microscope
Kevin Quigley. 2007.
FEATURE
INVENTER
LIGHT
MICROSCOPE
ELECTRON
MICROSCOPE
Jansen 1600's
Ruska 1933
MAGNIFICATION
up to x1500
x1 000 000
RESOLUTION
up to 0.2 µm
up to 0.0002 µm
ADVANTAGE
• living cells
• stains
• easy specimen
preparation
• high magnification
• high resolution
DISADVANTAGE
• low
magnification
• low resolution
• only non-living
cells
• expensive & long
specimen preparation
VISIBLE
STRUCTURES
• cell membrane
• cell wall
• chloroplast
• chromosomes
• cytoplasm
• mitochondria
• nucleolus
• nucleus
• all structures for
light microscope but
with greater detail
• endoplasmic
reticulum
(rough & smooth)
• Golgi body
• lysosomes
• ribosomes
Kevin Quigley. 2007.
So what are cells?
We now know that cells are the common
structural unit (the building blocks) of all
living things.
 They carry out various functions.
 Simple living things consist of only one
cell. They are called prokaryotic organisms.
 Organisms that have more than one cell are
called eukaryotic organisms

Kevin Quigley. 2006.
So what are cells?

Different cells differ greatly in structure and
function and can be grouped together in
multi-cellular organisms to form larger
complexes.
T. Preece 2007.
So what are cells made of?

Through vast advancements in technology,
we can now see what a cell is made up of.

Due to the use of microscopes, it was
discovered that cells are made up of smaller
parts called ‘organelles’.
Kevin Quigley. 2006.
Organelles

Each organelle has a different function
within the cell.

Read the following Hilarious Biology Jokes
and then complete the activity “Cell City
Project.”
T. Preece 2007.
Hilarious Biology Jokes...
2.
1.
Q: What is the fastest way to
determine the sex of a
chromosome?
A: Pull down its genes.
Q: A mushroom walks into a
bar and the bartender says
“Hey,... No Mushrooms
allowed!”
The mushroom replies Come
on mate... I’m a fun-gi.
T. Preece. 2007.