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Looking at Cells
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Microscopes: A basic biology tool that
allowed for the discovery of cells and
cell parts.
Scientists of Cells
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Robert Hooke was the English scientist (1665) who
discovered and named the cell while viewing a thin
slice of cork.
Anton van Leeuwenhoek—Dutch microscope maker
and textile manufacturer (1675) who was the first
to view living cells using a microscope.
Matthias Schleiden—German botanist (1838)
discovered that all plants were made of cells.
Theodore Schwann—German zoologist (1839)
discovered that all animals were made of cells.
Rudolf Virchow—German physician (1855)
discovered that cells can only come from preexisting cells after observing mitosis.
Cell Theory
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These scientists’ work helped to form
the Cell Theory:
All organisms are composed of one or
more cells.
The cell is the basic unit of
organization of organisms.
All cells come from preexisting cells.
Basic Cell Parts
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All cells are surrounded by a
membrane, and contain DNA and
cytoplasm. Most contain ribosomes.
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The fluid matrix within the cell is the
cytoplasm. It is a gelatinous fluid with
water as its main component. It helps
hold organelles in place and is the site
of many chemical reactions.
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Structures within cells that perform
specialized functions are calls
organelles. Ex—ribosome,
mitochondrion, and lysosome.
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Prokaryotic cells are cells that do not
contain a nucleus or membrane-bound
organelles. All bacterial cells are
prokaryotic or prokaryotes.
Prokaryotic organisms are all
unicellular. They do not have need for
different types of cells.
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Prokaryotes are the oldest living
organisms. Believed to be the first type
of cells on earth. Evolved before the
need for a nucleus. (Pro- before; karyonucleus)
Eukaryotic cells do contain a nucleus or
membrane-bound organelles. All cells
other than bacterial cells are eukaryotic
cells or eukaryotes
 Eukaryotic organisms can be unicellular
(protists) or multicellular (plants,
animals, fungi).
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Cell differentiation in multicellular,
eukaryotic organisms allows for
different types of cells. The shape of a
cell usually reflects its function.
Specialized Animal Cells
Muscle cells
Red blood cells
Cheek cells
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Specialized Plant cells
Guard Cells
Pollen
Xylem cells
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Cell Membrane
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The cell membrane is the outer
boundary of the cell which regulates
which materials enter and exit the
cell. Cell membranes are described as
selectively permeable or semipermeable.
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The cell membrane is made of a
phospholipid bilayer with embedded
proteins. The lipids are non-polar so
that makes the membrane a good
barrier to separate a cell from its
environment.
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The nucleus controls all cell activities,
especially growth and reproduction.
The nucleolus is a small dense area
inside the nucleus which makes rRNA
which is the main component of
ribosomes.
 Nucleoplasm
is the fluid matrix
inside of the nucleus. It is the
“cytoplasm” of the nucleus.
 There are different forms of DNA.
Chromosomes are the compact
versions of DNA that forms when
the cell is about to divide.
 Chromatin is the threadlike
genetic material found in the
nucleus of a nondividing cell.
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The nuclear envelope or nuclear
membrane is a porous doublemembrane that separates the nucleus
from the cytoplasm.
Ribosomes
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The ribosomes are the site of protein
synthesis. They can be found floating
freely within the cytoplasm or on the
rough ER.
E. R.
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The endoplasmic
reticulum (also
called ER) is a set of
tubular passageways
involved in the
transport of
materials throughout
the cell. It connects
the nucleus to the
cell membrane.
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There are two types of ER. Rough ER
is involved in the transport of proteins
and has many ribosomes attached to
its surface. Smooth ER is involved in
the manufacture and transporting of
lipids.
Cytoskeleton
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The cytoskeleton is a network of
protein filaments that helps the cell to
maintain its shape and function. It is
made of microfilaments and
microtubules.
Golgi Apparatus
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The Golgi Apparatus is responsible for
sorting and packaging compounds so
they can be sent to the appropriate
destination.
Mitochondria
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The mitochondria are organelles that
release energy from the stored food
molecules in the form of ATP. It is
also called the “powerhouse of the
cell”.
Vacuoles
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Vacuoles are storage sacs that store
food, water, wastes, salts, and other
material. They are larger in plant cells
than they are in animal cells.
Centrioles (Animals)
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The centrioles are found only in animal
cells and are tubular structures that
are involved in cell division.
Lysosomes (Animals)
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Lysosomes contain
powerful enzymes
that break down
substances to be
used by the cell as
well as toxic
substances. Poisons
and wastes are
detoxified within
the lysosomes.
Cell Wall & Chloroplast
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All plant cells are surrounded by a
nonliving layer called a cell wall which
provides protection and support for
the cell and helps give the cell its
shape.
Chloroplasts are found in plant cells
and are the site of photosynthesis.
Cilia & Flagella
Some cells use whip-like structures
called flagella for movement. This is
used as a paddle to move a cell through
liquid. Ex- Sperm.
 Cilia are hair-like projections that are
also used for movement. Many bacteria
have these.
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Cell Movement with Cilia &
Flagella
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