3.2 Cell Organelles
KEY CONCEPT Eukaryotic cells share many similarities.
3.2 Cell Organelles
Cells have boundaries
The Plasma Membrane
• Forms a boundary
between a cell and the
outside environment
• Controls the passage of
materials into and out of
the cell
• Helps to maintain
homeostasis
3.2 Cell Organelles
Cells have boundaries
• The plasma membrane is selectively permeable
- allows some, but not all materials to cross
Outside the Cell
Oxygen
Wastes
Invaders
CO2
Wastes
Water
Glucose
Inside the Cell
3.2 Cell Organelles
Cells have boundaries
Structure of the Plasma Membrane
• Composed of a phospholipid bilayer
3.2 Cell Organelles
Cells have boundaries
Other components in the Plasma Membrane
Proteins
• some span the entire membrane and help materials cross
• others are found on the inner and outer surface – anchoring
3.2 Cell Organelles
Cells have boundaries
Other components in the Plasma Membrane
• Cholesterol – strengthen the membrane
• Carbohydrates – cell identification
3.2 Cell Organelles
Cells have boundaries
• The Plasma membrane is referred as the fluid mosaic model
*Fluid - flexible
*Mosaic - pattern
3.2 Cell Organelles
Cells have boundaries
The Cell Wall
• A rigid structure located
just outside of the plasma
membrane
• Found in plants, fungi, most
bacteria, and some protists
• Provides protection and
support
• It is not selectively permeable
• In plants, it is composed of
cellulose
3.2 Cell Organelles
Cells have an internal structure.
The Cytoskeleton
- A network of protein fibers
that crisscross the entire cell
- Three types of fibers
a) Microtubules
b) Intermediate filaments
c) Microfilaments
3.2 Cell Organelles
Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
– helps position and transport organelles
– provides strength
– assists in cell division
– aids in cell movement
3.2 Cell Organelles
Cells have an internal structure.
The Cytoplasm
-Fills the space between
the nucleus and cell
membrane
-Consists of organelles
and cytosol(mostly water)
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
The Nucleus
• Storehouse of DNA
• Surrounded by a nuclear
membrane
• Nuclear pores allow large
molecules to pass
between the nucleus and
the cytoplasm
• The nucleolus is where
ribosomes are produced
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
The Endoplasmic Reticulum
• An interconnected network of folded membranes
• Important in synthesis and transport of cellular materials
• Two types – Rough ER and Smooth ER
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
Rough Endoplasmic Reticulum
• Has ribosomes attached
• Proteins are made by the
ribosomes on the
surface, and then
move inside the rough ER
to be packaged into a
vesicle
• The vesicle then takes
the protein to the Golgi
Apparatus
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
Ribosomes
• The site of protein
synthesis
• Can be found attached
to Rough ER or free in
the cytoplasm
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
Smooth Endoplasmic Reticulum
• No ribosomes attached
• Produces lipids
• Detoxification of drugs
and poisons
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
The Golgi Apparatus
• Closely layered stacks
of membrane – enclosed
spaces
• Modifies, packages, and
transports proteins
• The vesicles can then
be stored, transported,
or secreted
3.2 Cell Organelles
Some organelles transform energy in the cell
Mitochondria
• Bean shaped organelle
with a double membrane
• Produces ATP through
cellular respiration
• The cell uses the ATP for
energy
• Mitochondria have their
own ribosomes and DNA
C6H12O6 + 6 O2 = 6 CO2 + 6 H2O + ATP
3.2 Cell Organelles
Some organelles transform energy in the cell
The Chloroplast
• Organelles that carry out
photosynthesis
• Found in plant cells
• Has two membranes
• Contains chlorophyll
which absorbs light and
gives plants their green
color
• Also have their own DNA
and ribosomes
6 CO2 + 6 H2O + Light = C6H12O6 + 6 O2
3.2 Cell Organelles
Other organelles have various functions.
Vacuoles
• A membrane bound sac used for storage
Ex – water, food molecules, and enzymes
• Plant cells have
one large vacuole
• Animal cells have
many small vacuoles
3.2 Cell Organelles
Other organelles have various functions.
The Lysosome
• Membrane bound organelle
that contains digestive
enzymes
• Digests worn out organelles,
food particles, and engulfed
viruses or bacteria
• Numerous in animal cells
• Their presence in plant cells
is still questioned by some
scientists
3.2 Cell Organelles
Other organelles have various functions.
Centrosome and Centrioles
• The centrosome is a small
region of the cytoplasm that
produces microtubules
• In animals, it contains a pair
of centrioles
• Centrioles help DNA divide
during cell division
3.2 Cell Organelles
Other organelles have various functions.
Cilia
Flagella
• Short, numerous hair-like
• Long projection
projections
• Moves in a whip-like motion
• Move in a wave-like motion
• Used for locomotion
• Used for feeding and
locomotion