Cell Theory
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Cell Theory
This theory is one of the foundations of
biology.
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Antonie van Leeuwenhoek
The first man to witness a live cell under a
microscope was Antonie van Leeuwenhoek,
who in 1674 described the algae Spirogyra
and named the moving organisms
animalcules, meaning “little animals.”
In 1678, Antoni van Leeuwenhook reported
that he had observed “little animals” --
protozoa -- through a microscope, he also
called them “little beasties.”
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Robert Hooke
The cell was first discovered by
Robert Hooke in 1665. He
observed dead cork (cork comes
from the bark of a cork oak0
tree) and named the structures
he observed “cells” which
means small room.
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Theodor Schwann
Matthias Jakob Schleiden
Rudolf Virchow
In 1839, Schwann and Schleiden suggested
that cells were the basic unit of life.
In 1858, Rudolf Virchow concluded that all
cells come from pre-existing cells, thus
completing the classical cell theory.
Theodor Schwann, Matthias Jakob
Schleiden, and Rudolf Virchow are credited
with developing cell theory.
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Schwann
Schleiden
Virchow

Traditional rules of the
Cell Theory
1. All life forms are made
from one or more cells.
2. Cells only arise from pre-existing
cells.
3. The cell is the smallest
form of life.
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Modern rules of the
Cell Theory — 1
1 All known living things are
made up of cells. All organisms
are made up of one or more
cells.
2 The cell is structural &
functional unit of all living
things.
3 All cells come from pre-existing
cells by division. (Spontaneous
Generation does not occur).
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Modern rules of the
Cell Theory — 2
4 Cells contains hereditary
information (DNA) which is
passed from cell to cell during
cell division.
5 All cells are basically the same
in chemical composition.
6 All energy flow (metabolism &
biochemistry) of life occurs
within cells.
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Characteristics of Life
Living?
Homeostasis
Organization
Metabolism
Growth
Adaptation
Response to stimuli
Reproduce
Hereditary molecule is DNA
Viruses
 Bacteria are living organisms but
opinions vary on whether viruses are.
 A virus is an organic structures that
interacts with living organisms.
 It does show characteristics of life such
as having genes, evolving by natural
selection and reproducing by creating
multiple copies of themselves through
self-assembly.
 But viruses don't have a cellular
structure or their own metabolism;
they need a host cell to reproduce.
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 Viruses are the smallest and
simplest life form known. They are
10 to 100 times smaller than
bacteria.
Viruses
 Viruses must have a living host - like
a plant or animal - to multiply.
 Viruses are intracellular organisms
(they infiltrate the host cell and live
inside the cell). They change the
host cell's genetic material from its
normal function to producing the
virus itself.
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Two basic cell types
Prokaryotes
&
Eukaryotes
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Two basic cell types
Prokaryotes
&
Eukaryotes
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PPrrookkaarryyootteess
The lack of a nucleus gives prokaryotes their name.

PPrrookkaarryyootteess
 The prokaryotes are a
group of organisms that
lack a cell nucleus, or any
other membrane-bound
organelles.
 They differ from the
eukaryotes, which have a
cell nucleus.
 Most are unicellular, but
a few prokaryotes such as
myxobacteria have
multicellular stages in
their life cycles.
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Prokaryotes
 The prokaryotes are divided into
two domains: the bacteria and the
archaea.
 Archaea were recognized as a
domain of life in 1990.
 These organisms were originally
thought to live only in inhospitable
conditions such as extremes of
temperature, pH, and radiation
but have since been found in all
types of habitats.
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Eukaryotes
The presence of a nucleus gives eukaryotes their name.
Greek Meaning
eu good, noble, true
karyon nut, kernel

Eukaryotic
A eukaryotic is an
organism whose
cells contain
complex
structures inside
the membranes.
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 The most important
membrane-bound structure
setting eukaryotic cells
apart from prokaryotic cells
is the nucleus, or nuclear
envelope, within which the
genetic material is carried.
 Most eukaryotic cells also
contain other membrane-bound
organelles such as
mitochondria, chloroplasts
and the Golgi apparatus.
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Eukaryotic

Organelles
Found only in eukaryotic cells
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Nucleus
The “control center,”
it maintain the integrity
of these genes and to
control the activities of
the cell by regulating
gene expression.
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Nucleolus
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Function:
Ribosomal RNA (rRNA)
is transcribed and
assembled within the
nucleolus.

Cell Membrane or Plasma Membrane
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Function:
It separates the interior of
a cell from the outside
environment. The cell
membrane surrounds all
cells and it is semi-permeable,
controlling the
movement of substances in
and out of cells.

Cell Wall
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 Provides these cells with
structural support and
protection, and also acts as a
filtering mechanism. A major
function of the cell wall is to
act as a pressure vessel,
preventing over-expansion
when water enters the cell.
They are found in plants,
bacteria, fungi, algae, and
some archaea.

Ribosome
 Make proteins from amino acids.
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Vesicle
Membrane-enclosed
sac that stores or
transports substances
within a cell.
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Rough Endoplasmic Reticulum (RER)
Ribosome to bind to
the RER and pass the
new protein through
the ER membrane.
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Smooth Endoplasmic Reticulum (SER)
 Several metabolic processes,
including synthesis of lipids and
steroids, metabolism of
carbohydrates, regulation of calcium
concentration, drug detoxification,
attachment of receptors on cell
membrane proteins, and steroid
metabolism.
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Golgi apparatus
Processes and packages
macromolecules, such as
proteins and lipids, after their
synthesis and before they
make their way to their
destination; it is particularly
important in the processing of
proteins for secretion
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Cytoskeleton
 It is a dynamic structure that
maintains cell shape, protects the
cell, enables cellular motion (using
structures such as flagella, cilia and
lamellipodia), and plays important
roles in both intracellular transport
(the movement of vesicles and
organelles, for example) and cellular
division.
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Mitochondria
 Generate most of the cell’s supply of
adenosine triphosphate (ATP), used
as a source of chemical energy. In
addition to supplying cellular
energy, they are involved in a range
of other processes, such as signaling,
cellular differentiation, cell death, as
well as the control of the cell cycle
and cell growth.
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Vacuole
 The function and importance of vacuoles varies greatly
according to the type of cell in which they are present,
having much greater prominence in the cells of plants, fungi
and certain protists than those of animals and bacteria. In
general, the functions of the vacuole include:
 Isolating materials that might be harmful or a threat to
the cell
 Containing waste products
 Maintaining internal hydrostatic pressure or turgor
within the cell
 Maintaining an acidic internal pH
 Containing small molecules
 Exporting unwanted substances from the cell
 Allows plants to support structures such as leaves and
flowers due to the pressure of the central vacuole
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Cytoplasm
 Are filled with liquid that is kept separate
from the rest of the cytoplasm by
biological membranes. The cytoplasm is
the site where most cellular activities
occur, such as many metabolic pathways
like glycolysis, and processes such as cell
division.
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Lysosome
Lysosomes digest
excess or worn-out
organelles, food
particles, and
engulfed viruses or
bacteria.
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Centrioles within Centrosome
 These are involved in the organization of
the mitotic spindle and in the completion
of cytokinesis (the process in which the
cytoplasm of a single eukaryotic cell is
divided to form two daughter cells).
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Chloroplasts
Chloroplasts capture light
energy to conserve free
energy in the form of ATP
and reduce NADP to
NADPH through a complex
set of processes called
photosynthesis.
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Organelles
PPllaannttss
Cell Membrane
Cell walls
Chloroplasts
Vacuoles
 Lysosomes
Golgi Bodies
Mitochondria
Endoplasmic Reticulum
(ER)
Ribosomes
AAnniimmaallss
Cell Membrane
Centrioles (used in cellular
reproduction)
Vacuoles
Lysosomes
Golgi Bodies
Mitochondria
Endoplasmic Reticulum
(ER)
Ribosomes
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Cell Theory Rap
Listen close to the story I tell.
It’s the rapping story of the living
cell.
It’s a happy tune that’s sort of
cheery.
About a real tough topic called the
cell theory.
All animals, plants, and protists
too,
Are made of cells with different
jobs to do.
They’re the basic units of all
organisms,
And I hope by now you got the
rhythm.
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It all started with one dude named
Hooke.
Who at some cork cells took a
look.
He used a scope and took his time.
‘Cause a cell is small and thinner
than a dime.
Say 1, 2, 3, 4,
Are you ready to learn some
more?
The animal cell has many parts,
And you must know each one by
heart.
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Like the farmer man in the dell.
The nucleus controls the cell.
its gives the orders -- kind of like a
brain.
And it’s protected by a nuclear
membrane.
Around the cell, you’ll find another
“skin,”
The cellular membrane holds the
whole cell in
But its job isn’t simple there’s no
doubt,
It lets some particles go in and out.
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Now please don’t lose your science
enthusiasm,
Listen to the story of the
cytoplasm.
All around the cell this thick fluid
does go,
But in the nucleus it will not flow.
And don’t forget those ribosomes -
This is where proteins come from.
These protein factories are so
small, you’ll agree,
You need an electron microscope
to see.
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Just when you thought you
weren’t having any fun,
Along comes teh endoplasmic
reticulum.
These tubelike structures serve as
a track,
To carry stuff to the membrane
and back.
Now have you ever seen any
doughnuts without holes?
In a cell, they’re called vacuoles.
They’re filled with stuff like H2O
And they carry food so the cell can
grow.
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Las of all, but not the very least,
Mitochondria - mighty cellular
beasts,
Since they turn sugars into energy
so well,
We call them the powerhouse of
the cell.
Now my friend, you know it well,
The unforgettable story of the
living cell.
“Science World”
10-5-90
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