CELL ORGANELLES &
FEATURES
Plasma Membrane
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Recall: what is a plasma
membrane?
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*Found in both plant & animal
cells
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A cell’s outer boundary
In a plant cell: lies beneath the cell
wall
In animal cells: the outer boundary
(made of cholesterol)
Provides cell with:
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Protection
Control of movement of materials in
and out of cell
Support
Maintains condition of cell
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Membrane Lipids
Primarily made of
phospholipids that have
hydrophilic head and
hydrophobic tail
 Create a phospholipid bilayer
 Cell membranes in eukaryotes
contain lipids called sterols
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Important because it helps make
the membrane more firm & keeps
it from freezing at low
temperatures
Nucleus
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Recall: What is a nucleus?
 Membrane-bound organelle that
contains a cell’s DNA
*Found in both plant & animal cells
Most of the functions of a
eukaryotic cell are controlled by the
nucleus
Houses and protects the cell’s
genetic information (DNA)
The site where DNA is transcribed
into RNA
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Nuclear Envelope
 Nucleus is surrounded by a double membrane called the nuclear
envelope
 Made up of two phospholipid bilayers
Nucleolus
 The site where DNA is concentrated when it is making ribosomal
RNA; makes ribosomes
Mitochondria
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*Found in both plant & animal cells
Mitochondria: tiny organelles that
transfer energy from organic molecules
to adenosine triphosphate (ATP)
Have their own DNA (called
mitochondrial DNA)
Have an inner and outer phospholipid
bilayer
 Inner membrane has many folds
called cristae
 Cristae contain proteins that carry
out energy-harvesting chemical
reactions
Ribosomes
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*Found in both plant & animal cells
Ribosomes: small, roughly spherical
organelles that are responsible for
building protein
Do not have a membrane
Made of protein and RNA
molecules
Assembly begins in the nucleolus
and is completed in the cytoplasm
Some are free within the cytosol &
some are attached to the rough
endoplasmic reticulum
Endoplasmic Reticulum
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*Found in both plant & animal
cells
Endoplasmic reticulum (ER): a
network of membranous tubes
and sacs, called cisternae
Located next to the nucleus
Functions primarily as an
intracellular highway
Transports materials throughout
the cell
Two types:
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Smooth (no ribosomes)
Rough (covered with ribosomes)
Golgi Apparatus
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*Found in both plant & animal
cells
Golgi apparatus: network of
flattened, membranous sacs that
processes and packages
molecules, like lipids and proteins,
that were made by the cell
Proteins get “address labels” that
direct them to the other parts of
the cell
Lysosomes
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*Found in animal cells only!
Lysosomes: vesicles that bud from the
Golgi apparatus and that contain
digestive enzymes
Break down large molecules, such as
proteins, nucleic acids,
carbohydrates, and phospholipids
Responsible for breaking down cells
when it is time for the cell to die
Play an important role in maintaining
an organism’s health by destroying
cells that are no longer functioning
properly
Cytoskeleton
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*Found in both plant & animal cells
Cytoskeleton: network of thin tubes
and filaments that crisscrosses the
cytosol
Strengthen cell & maintains the
shape
Moves organelles within the cell
*Note: Only animal cells have
special microtubules called centrioles
that are important for cell division
*Features Unique to Plant Cells
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Plant cells have three
additional kinds of
structures that are
extremely important to
plant function:
 Cell walls
 Large central vacuoles
 Plastids
Cell Wall
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Cell wall: a rigid layer
that lies outside the cell’s
plasma membrane
Main component of the
cell wall is cellulose
Some plants also produce
a secondary cell wall
Central Vacuole
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Central vacuole: large,
fluid-filled organelle that
stores not only water but
also enzymes, metabolic
wastes, and other materials
Can make up 90% of the
plant cell’s volume
Helps to keep the plant
tissue firm
*Note: animal cells have
vacuoles, but they are very
small in comparison to
plant cell vacuoles
Plastids
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Plastids: organelles
surrounded by a double
membrane and contain
their own DNA
Several types of plastids,
including chloroplasts,
chromoplasts, and
leucoplasts
Chloroplasts
 Use light energy to make
carbohydrates from carbon dioxide
and water
 Contains a system of flattened,
membranous sacs called thylakoids
 Thylakoids contain a green
pigment called chlorophyll
 Chlorophyll: the main molecule
that absorbs light and captures
light energy for the cell
Plant Cells vs. Animal Cells
Plant Cell
Animal Cell
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Cell wall present
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Lysosomes
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Large central vacuole
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Centrioles
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Plastids (chloroplasts)
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Vacuoles are very small
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Larger in size
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Smaller in size
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Fixed shape
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No definite shape
Cell City
The Cell Song