Cells and Their Amazing
Organelles
Cells can be …
Prokaryotic no membrane bound
organelles
Eukaryotic membrane bound
organelles
Eukaryotic cells include …
Plant Cell
Animal Cell
Why are cells so small?
• As cell size increases
the volume increases
much faster than the
surface area.
• Cells obtain nutrients,
gain information and rid
waste through their
plasma membrane.
Ratio of Surface Area:Volume
As cell size increases, it’s ability
to exchange materials with its
environment becomes limited by
the amount of membrane area
that is available for exchange.
Cell Membrane
• Outer boundary of all
cells .
• Described as being a
fluid mosaic.
• Semi-permeable:
controls what enters and
leaves the cell.
Fluid-mosaic model of membrane structure
How molecules cross the plasma membrane
Vesicles
• Membranous structures
that derive from other
membranous cellular
parts.
• Carry substances from
one part of the cell to
another.
• Bind to the correct region
if protein receptors are
compatible.
Cytoplasm
• Consists of the
cytosol (liquid)
and all of the
organelles within
cell .
The Nucleus
• Controls most
activities in the cell
by controlling
protein production.
• Contains all genetic
information in the
form of DNA.
• Nucleus is surrounded
by the nuclear
envelope - a double
membrane
• The nuclear envelope
has nuclear pores that
control entry and exit
of materials
The Nucleolus
• A darkened region
where ribosomes
(ribosomal RNA)
is synthesized
Ribosomes
• Composed of a large and
small sub-unit of RNA
• Make proteins in the
cell.
• May be free-floating in
cytoplasm or attached to
endoplasmic reticulum.
Free Floating
Ribosomes
Ribosomes
on ER
Endoplasmic Reticulum
• Series of folded
membranes that form
sacs or tubes.
• Rough ER has
ribosomes attached.
• Smooth ER doesn’t
have ribosomes.
Smooth Endoplasmic Reticulum
• The site for:
- synthesis of steroids
and other lipids,
- Ca++ storage in
muscle cells,
- detoxification of
drugs, toxins, alcohol
(especially in liver
cells)
Rough Endoplasmic Reticulum
• The site where proteins
are made to be used
inside or outside of cell.
• Once proteins are made
they are packaged into
vesicles to be “shipped”
to Golgi apparatus.
Golgi Apparatus
• Saclike membranes
used for storing,
modifying and
packaging of
proteins and other
chemicals.
Endomembrane System
Proteins made by Rough
ER are shipped to Golgi
Apparatus in vesicles
where they are modified.
From here they move to
the cell membrane in
secretory vesicles which
release them externally.
nucleus
nucleolus
rough ER
ribosomes
smooth ER
vesicle
lipids
Golgi apparatus
vesicle
cell membrane
Lysosomes
• Formed in Golgi
bodies
• Contain hydrolytic
(digestive) enzymes
to break down
unwanted particles
• Help white blood cells
to destroy bacteria
Mitochondria
• Produce ATP through
cellular respiration
• Mitochondria replicate
by binary fission similar to prokaryotic
cell division
Mitochondrial Structure
- have double membrane structure
- inner membrane folded into inward projections called cristae
- two spaces within the mitochondrion - the matrix and the
intermembrane space
Chloroplasts
• sites of
photosynthesis in
nearly all plants and
some protists.
• trap light energy and
convert it into
chemical energy
Chloroplast Structure
- have double membrane structure
-Within the stroma (fluid) are a series of stacks of flattened
-membranous structures called thylakoids (stacks of these are
called grana)
Cytoskeleton
• Composed of proteins that
maintain the cell’s structure,
transport materials, and
position and move
organelles.
• 3 cytoskeletal components:
microtubules
actin filaments
intermediate filaments
Actin Filaments
• involved in cellular and
organelle movement.
• smallest components of
the cytoskeleton.
• “Motor” molecules
Intermediate Filaments
• involved in anchoring
organelles in place and
•holding cells together .
Microtubules
- hollow tubes made of proteins called tubulin dimers.
-These are responsible for cell movement by changing in length
by adding/taking away tubulin dimers polymerization/
depolymerization
-Work with actin in the movement of organelles.
- These are the largest components of the cytoskeleton.
Cellular Work
- Microtubules work with actin (and other motor
molecules) in the movement of organelles and other
cellular structures.
- These are the largest components of the cytoskeleton.
Cilia/Flagella Movement
• A flagellum has pairs of
microtubules in a 9+2
pattern each pair of tubules
has short arms of dynein (a
motor molecule) that pulls
on neighboring tubules
causing the structure to
twist throughout.
Back to Plant Cells
Contain:
• chloroplasts
• A cell wall
• A large central
vacuole
• No centrioles
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