Cell Structures
Cell Unit
Discovery of Cells
 Robert
Hooke (1660’s)
– first to observe non-living cells in cork
and named them cells
 Anton
van Leeuwenhoek (1680’s)
– first to observe living cells in lake water
and teeth scrapings
The Cell Theory
 Developed
by Schleiden, Schwann,
and Virchow (1800’s)
 Important points:
– All living things are made of one or
more cells.
– Cells are the basic unit of structure and
function in living things.
– All cells come from other cells.
2 Basic Types of Cells
 Prokaryotes
(prokaryotic cells)
– Cells that DO NOT have a nucleus
– Examples: bacteria
 Eukaryotes
(eukaryotic cells)
– Cells that DO have a nucleus and
other organelles
– Examples: plant cells and animal
cells
Cell Structures
 Specialized
structures that perform
specific functions in the cell are
called organelles.
 Organelle means “little organ”.
Cell Wall
 Physical
Description: a rigid layer of
nonliving material that surrounds plant
cells
 Function: protects and supports the
cell
 Type of Cell: Found in plant cells
 Analogy: Walls of school
Cell Membrane
 Physical
Description: thin, flexible
barrier around the cell (just inside
the cell wall OR the outside border of
animal cells)
 Function: controls what enters and
leaves the cell
 Type of Cell: found in all cells
 Analogy: the security system of the
school
Nucleus
 Physical
Description: large organelle
that is usually near the center
 Function: controls the cells activities
 Type of Cell: found in all eukaryotes
 Analogy: the office of a school
Nuclear Envelope (Membrane)
 Physical
Description: Small spherical
structure within the nucleus that
holds in strands of genetic material
(DNA)
 Function: Hold in genetic instructions
for the cell to do its job
 Type of Cell: found in all eukaryotic
cells
 Analogy: the walls of the office
Chromatin
 Physical
Description: Thin strands of
genetic material
 Function: The genetic instruction for
the cell to do it’s job
 Type of Cell: found in both
eukaryotic and prokaryotic cells
 Analogy: the principal him/herself
Nucleolus
 Physical
Description: Small dark
structure within the nucleus
 Function: Create ribosomes
 Type of Cell: found in all eukaryotic
cells
 Analogy: the substitute teacher
Cytoplasm
 Physical
Description: the fluid-like
material inside the cell membrane
 Function: contains the organelles;
“cell jelly” and is a site for chemical
reactions
 Type of Cell: found in all cells
 Analogy: the air inside the school
Mitochondria
 Physical
Description: “bean-shaped”
organelle that has a folded inner
membrane
 Function: breaks down FOOD to
release energy for use by the cell
 Type of Cell: found in all eukaryotes
 Analogy: the boiler and generator of
the school
Endoplasmic Reticulum (ER)
 Physical
Description: internal
membrane system
– Rough - has ribosomes
– Smooth- no ribosomes
 Function:
assembles parts of cell
membrane and modifies proteins
 Type of Cell: found in all eukaryotes
 Analogy: the copy room of a school
Ribosomes
 Physical
Description: tiny, round
structures either attached to the ER
or floating in cytoplasm
 Function: makes proteins
 Type of Cell: found in all eukaryotes
AND some prokaryotes
 Analogy: the teachers in a school
Golgi Apparatus
(aka Golgi Body)
 Physical
Description: stack of
membranes in the cytoplasm
 Function: receives proteins and other
materials from ER; gives proteins the
“address” of their final destination
 Type of Cell: found in all eukaryotes
 Analogy: the busses of a school
Chloroplast
 Physical
Description: tubular
organelle that contains chlorophyll (a
green pigment)
 Function: use energy from
SUNLIGHT to MAKE FOOD through
photosynthesis
 Type of Cell: found in many plant
cells
 Analogy: the solar energy panels of a
school
Vacuole
 Physical
Description: large, spacious
sack in the cytoplasm
 Function: stores materials for the cell
(water, food, waste, etc…)
 Type of Cell: found in all eukaryotes
(usually one large vacuole in plants
and many small vacuoles in animals)
 Analogy: the storage closet of a
school
Lysosome
 Physical
Description: small, round
sacks in the cytoplasm
 Function: breaks down large food
particles and old or damaged
organelles
 Type of Cell: found in all eukaryotes
BUT are very rare in plant cells
 Analogy: the janitor of a school
Plant Cells vs. Animal Cells
 Cell
Wall
 Chloroplasts
 Lysosomes are
rare
 1 Large Vacuole
 No
Cell Wall
 No Chloroplasts
 Lysosomes are
common
 Several Small
Vacuoles
Job of Cells
The
main job of all cells is to
make proteins
 Different
cells make different types
of proteins for different functions
 Steps of protein production:
1) Ribosome
2) Endoplasmic Reticulum
3) Golgi Apparatus
4) Final Destination of the Protein
(may be outside of the cell)