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Cell Theory
Cells and Cell Organelles
The cell theory states:
All organisms are composed of one or more cells.
Cells are the basic unit of structure and function in
organisms.
All cells come only from other cells.
How many cells in your body?
• 50 million million (trillion)
• That’s 50,000,000,000,000 cells!!!!!!
• And not only that, there are many
different types.
• Cells are diverse
– But only two BASIC types
Two Basic Cell Types
Prokaryote
Eukaryote
Name
Pro = before
karyote = nucleus
Eu = true
karyote = nucleus
Relative size
very small
large
True
Nucleus
present
No
yes
Organelles
Present
No
Yes
DNA
structure
loose, sometimes
circular
packed into
chromosomes
Examples
Bacteria
Plants, animals, protists
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Prokaryotic Cell
• Note the lack of nucleus, DNA free floating
• DO HAVE cell membrane, ribosomes, and
cell wall (sometimes)
Eukaryotic Cell
• DO HAVE a membrane-bound nucleus
• DO HAVE membrane-bound organelles: mitochondria,
chloroplasts (plants), cell wall (plants), smooth and
rough endoplasmic reticulum, golgi apparatus,
lysosomes, vacuoles, etc.
Relative sizes-- Note that:
Eukaryotic Cell
Prokaryotes (bacteria)
are 1-10 µm.
Eukaryotes (plant and animal
cells) are 10-100 µm
Lots of internal
membranebound
structures!
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Cell Membrane
Cell Membrane
• Both prokaryotic and eukaryotic cells have
this “cell membrane”
• Holds the CYTOPLASM inside the cell and
keeps unwanted things out of the cell
• Gives cells their shape and flexibility
• Helps to maintain HOMEOSTASIS by
allowing certain substance to flow in and out
of the cell – SELECTIVE PERMIABILITY
of Cell Membrane
Structure
• The cell membrane is a PHOSPHOLIPID
• PHOSPHOLIPID
Hydroph
H yd
ro p
Structure of the Cell Membrane
BILAYER
Fluid Mosaic Model
Phospholipids, cholesterol, and proteins that
make up the cell membrane all flow like the
surface of a wavy lake, moving and shifting.
BILAYER
ilic head
hob
ic ta
il
Water
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Fluid Mosaic Model
Cell Walls
• Located outside the cell membrane
• Can be made of thick fibers of cellulose
(plants), chitin (fungi), or peptodoglycan
(some bacteria)--all of these are carbs
• Animal cells DO NOT have cell walls
Cell Wall of Plants
Nucleus
Is this a prokaryotic or eukaryotic cell?
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Nucleus
• Control Center of the cell
• Contains CHROMATIN (loose DNA)
– Bundles into CHROMOSOMES when cell is ready to
divide (it packs before moving)
• Contains a NUCLEOLUS, which is made up of a
mass of nucleotides used for making DNA and
RNA
Chromatin
Chromatin in the Nucleus
• Directs PROTEIN SYNTHESIS
(building proteins)
• It contains the “blueprints” for the
organism; this is the DNA
Chromosomes
The Nucleus and the Nuclear Membrane
Outside the Nucleus:
the Cytoplasm
The Nuclear Membrane or Envelope is a double membrane with pores to let
certain things in and out of the nucleus.
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Outside the Nucleus:
The Cytoplasm
Endoplasmic Reticulum (ER) and
Ribosomes
• Lots of action!
• Many organelles and ribosomes are
floating around
• Cytoplasm includes organelles and the
gel-like fluid they are suspended in
Smooth and Rough Endoplasmic Reticulum
The endoplasmic reticulum (ER) is a system of membrane
channels and little sacs that acts as a “workspace” for
cellular reactions.
Smooth and
Rough ER
Rough ER is studded with ribosomes and is where
proteins are made and processed.
Smooth ER has no ribosomes and is where the cell
makes phospholipids and packages proteins into vesicles
(small storage sacs), among other functions.
Ribosomes can be attached to ER or free. They are tiny
organelles that make proteins.
After leaving the ER, proteins are often sent to the Golgi
for folding and finishing.
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Golgi Apparatus
Smooth and
Rough ER
Golgi Apparatus and
Lysosomes
Golgi Apparatus:
• A flattened set of membranes
• The “post office” of the cell
• Processes and packages proteins for export
• Makes lysosomes
Lysosomes:
• Small sacs full of hydrolytic (digestive)
enzymes
• Break apart (digest) foreign substances
Golgi Apparatus And Lysosomes
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Vacuoles
Vacuoles
Used for storage
– Waste products
– Food and water
– Enzymes, etc.
– In plants, this is usually very large, called a
central vacuole
Mitochondrion
Mitochondrion
•
•
•
•
plural = mitochondria
The “powerhouse” of the cell
Double membrane
Site of CELLULAR RESPIRATION
– Releases energy from food molecules
– Creates ATP, an energy containing molecule that
acts as a “battery” to power other cell reactions
– ATP is the “energy currency” of the cell
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Mitochondrion
Chloroplast
Chloroplast
Chloroplast
• Only found in green plant cells
• Trap energy from sunlight to build food
molecules
– Stored for later use
• Double membrane
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The Cytoskeleton
The eukaryotic cytoskeleton is a network of
microfilaments and microtubules that
extends from the nucleus to the plasma (cell)
membrane.
Microfilaments and microtubules:
•Give cell its shape
•Help organelles move within the cell
•Help the cell move
Centrioles
Centrioles are short
cylinders made of
microtubules.
Centrioles are only found
in animal cells and are
involved in building and
taking apart microtubules
during cell division and in
the organization of cilia
and flagella.
Cilia andFlagella
Cilia (small and numerous) and flagella (large and
single) are made of microtubules and are involved
in cell movement.
End of Show
• Extra pictures follow
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Animal Cell Anatomy
Plant Cell Anatomy
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