Cells
The Basic Units of Life
Cell Theory
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Robert Hooke was the
first person to describe
cells in 1665.
He observed cork cells
and plant cells, which
are easier to see
because of a cell wall.
Animal cells are harder
to see, so he thought
animals weren’t made
up of cells since he
couldn’t see them.
Anton van
Leeuwenhoek
 Discovered
animalcules (which means
little animals)
 Now known as Protists (single-celled
organisms)
 Discovered cells in animal blood.
 Found differences between blood cells of
different animals.
 First person to see bacteria
Cell
Theory
Matthias Schleiden and Theodor
Schwann
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Schleiden studied plants –
Discovered all plants are
made of cells
Schwann studied animals
– discovered that all
animal tissue is made of
cells.
Schwann wrote first 2
parts of cell theory
 All
organisms
are made of
one or more
cells
 The cell is the
basic unit of all
living things
Cell Theory
 Rudolf
Virchow added the 3rd part to the
cell theory in 1858
All
cells come from
existing cells
Common cell parts
 There
are many different types of cells –
 But all cells have a few parts in common
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Cell membrane and cytoplasm
Organelles
Genetic material
Cell Membrane & Cytoplasm
 All
cells are surrounded by a cell
membrane
 The cell membrane is a protective layer
that covers the cell’s surface and acts as
a barrier
 It also controls materials going into and
out of the cell
 Cytoplasm is the fluid inside a cell
Organelles
 Structures
that perform specific functions
within the cell.
 Most are surrounded by membranes
 Some float in the cytoplasm
 Some are attached to membranes or
other organelles
Genetic Material
 All
cells contain DNA
 DNA is the genetic material that carries
information needed to make new cells
and new organisms
 DNA is passed from parent to offspring
and controls the activities of a cell
2 Types of Cells
 Prokaryotes
and eukaryotes
 Prokaryotes are single-celled organisms
that do not have a nucleus or membranebound organelles
 Eukaryotes are an organism made of
cells that have a nucleus enclosed by a
membrane
Prokaryotes
 Single-celled
organism
 Do not have a nucleus
 Ex: Bacteria and Archaea
 Bacteria are the most common
prokaryote
 No Nucleus, no membrane-covered
organelles
 Do have ribosomes, and a strong cell wall
Eukaryotes
 Largest
cells – 10 times larger than
bacterial cells
 Contain a nucleus and membrane-bound
organelles
 All living things that are not bacteria or
archaea are made up of one or more
eukaryotic cells
 Many eukaryotic organisms are multicellular (many cells)(plants, animals, fungi)