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Cells are…
The extremely tiny building blocks of living things.
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So, if they are extremely tiny…
How do we know they are there?
You only get one guess… 
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In science, the tools (or technology) often must
be invented before we can make new discoveries.
Cells were discovered and studied after the
invention of microscopes…
Plant Cells
(or tissue)
Euglena
Amoeba
Animal Cells
(or Tissue)
How were cells first discovered, named, and studied?
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A Brief History of the Microscope and the
Beginnings of Microbiology
Robert Hooke
1665 – Robert Hooke designed the compound microscope
that enabled scientists to see the microscopic world. He is
credited with discovering and naming “cells.” He described
what he observed. The boxlike cells of cork reminded him of
the cells of a monastery walls, which in fact were the cells in
cork tissue.
Antony van Leeuwenhoek (1632-1723)
1673 - Hooke’s early compound microscopes could not
magnify objects more than twenty or thirty times natural
size. Leeuwenhoek was skilled at grinding lenses. This
allowed him to build microscopes that magnified over 200
times. These microscopes had clearer and brighter images
than any of his colleagues’ microscopes. Although he could
not draw well, he hired an illustrator to prepare drawings of
the things he saw to accompany his written descriptions.
Microscope Practice…Click HERE!
http://micro.magnet.fsu.edu/primer/java/microassembly/index.html
Leeuwenhoek’s
Microscope
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Better Microscopes
Led to the Development of the Cell Theory…
Botanist
Matthias Schleiden (1804-1881)
Schleiden observed that
all plants seemed to be
composed of cells
Anatomist
Théodore Schwann (1810 – 1882)
Schwann extended
Schleiden's cell theory to
animals
Schleiden and Schwann:
 proposed that all plants and animals were made of cells.
 observed organisms that were unicellular and multicellular.
 observed common cell structures such as membranes and nuclei.
 made comparisons of various animal and plant tissues.
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Rudolph Virchow(1821-1902)
Physician / Pathologist
1855 – While experimenting with diseases he found that all cells
come from other existing cells.
Thus, he completed what is known as the cell theory: “cells give rise
to other cells; even multicellular organisms begin as single cells.”
Plant cell division
Animal cell division
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Schleiden, Schwann, and Virchow contributed to
The Cell Theory:
1. All living things are made up of one or
more cells.
2. Cells are the basic units of structure and
function in living things.
3. New cells come from existing cells.
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Technological Advances
The 20th century brought many technological advances that
allowed scientists to better understand the structure and
function of cells...
such as the scanning electron
microscope (SEM).
The SEM produces magnified images
like this one that scientists can use
to study cells in more detail.
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Cell Basics
Certain structures are common to most
eukaryotic cells:
cell membrane - outer
boundary of the cell
nucleus - control center
cytoplasm - material between the
cell membrane and the nucleus
cell wall – some cells have this strong
layer around the cell membrane
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Nucleus
mRNA
&
Co
Manager & Design Team
Contains genetic material
Directs the making of proteins
Manages cell activities
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Cytoplasm
Cytoplasm - material between the cell membrane and the nucleus
Golgi Apparatus
Organelles in the Cytoplasm
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Chloroplasts
In Plant Cells and Energy Producing Protists
Makes Fuel
Into Fuel
Chloroplasts use the energy from sunlight
to make energy-rich food molecules in a
process known as photosynthesis.
Food/Energy
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ATP
Mitochondria
Power Generator
ATP
ATP
Mitochondria
Function: Changes food energy into
high-energy compounds called ATP a
cell can use
The cell can use the energy to power
growth, development, and movement.
ATP
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Protein … Design to Product.
The manufacturing of proteins is perhaps the
most important function of the cell.
Endoplasmic Reticulum
Ribosomes
Transports materials in the cell
The code to make
proteins is sent to the
ribosomes and proteins
are constructed.
Modifies, sorts,
packages, and
transports substances
in the cell
Exports proteins to
their final
destination
(or other food energy)
Chloroplasts
Golgi Bodies
Mitochondria
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Lysosomes
Garbage Collectors
 Filled with enzymes that aid in the disposal of the cell’s wastes
 Break down and digest materials
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Vacuoles
Storage Tanks
 Most plant cells have a large central
vacuole filled with liquid.
 Vacuoles are saclike structures that store
materials such as water, salts, proteins,
and carbohydrates.

Animal cells lack a large central vacuole
but may contain smaller vacuoles.
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Cell Membrane
Gate Keeper
Allows what enters and
leaves the cell
Aids in protection & support
Maintains balance
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Homeostasis
The Cell Membrane:
Keeping Internal Conditions in Balance
 The cell membrane functions as a semi-permeable
barrier - like a fence.
 This means it allows some molecules in and
out while preventing others from crossing.
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Cell Wall
 Cell walls provide support and
protection.
 Plants, algae, fungi, and nearly all
prokaryotes have cell walls.
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Ribosomes often
are on the E.R.
Endoplasmic Reticulum
Ribosomes
This is a package”
breaking away to be
for exporting
Golgi Bodies
Nucleus
Mitochondria
Lysosome
Vacuole
Chloroplast
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Ribosomes
Chloroplast
Nucleus
Mitochondria
Golgi Bodies
Lysosome
Vacuole
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Specialization of Cells
In multi-cellular organisms,
cells are uniquely suited to
perform a particular function.
Certain cells are specialized
to move, react, protect, or
produce special substances.
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Levels of Organization
 In multicellular
organisms, cells are
organized to form
tissues.
Cells
Tissues
 Several types of tissues
form organs.
 Many different organs
form organ systems
that make up the
organism.
Organs
Organ
Systems
Organism
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