Eukaryotic
Cell
Structures
Eukaryotic Cells
•  A Eukaryote is any organism whose
cells contains a nucleus and
membrane-bound organelles/
structures.
•  Animals and plants are eukaryotes
and thus are made of many eukaryotic
cells.
•  FYI: Bacteria are “prokaryotes”. We’ll
get to these later!
Eukaryotic Cells
•  Compared to Prokaryotic:
–  Bigger (typically)
–  Contains a Nucleus
–  Contains Organelles- specialized subunits within
a cell that performs a specialized function – is
usually enclosed within its own lipid bilayer
–  Ribosomes are different from prokaryotes
(usually larger in eukaryotes)
–  Single OR multi-cellular organisms
•  Lets look at structures found in both plants
and animals
Cell Membrane
•  Phospholipid bilayer
•  “Gatekeeper” of the cell
Controls what goes in and out of the cell
•  Enzymatic activity
•  Cell identification
Cytoplasm/Cytosol
•  The fluid of the cell = cytosol
–  Mostly water with lots of molecules and
ions
•  Cytosol + organelles = cytoplasm
•  Chemical reactions take place in the
cytoplasm
•  Like the “factory floor”
•  archaic name: hyaloplasm
Cytoskeleton
•  Framework of microtubules and
microfilaments
•  Constantly shifting due to cell’s needs
•  Provides support, shape, traffic flow
Ribosomes
•  Made up of RNA (rRNA) and proteins
•  Assembles amino acids into proteins
(the main “product” produced and
needed for the cell)
–  Like a “factory worker”
Rough Endoplasmic Reticulum
(ER)
•  Folded membranes studded with
ribosomes
•  Makes, modifies, and channels
proteins
•  Like an “assembly line” for the
ribosomes to work on
Smooth E.R.
•  Folded membranes, with no ribosomes
•  Makes lipids
•  Assembly line, but different products
Golgi Apparatus
(aka golgi complex, golgi body)
•  Flattened sacs of membranes
•  Sorts, packages and modifies
substances for transport
–  Especially proteins (enzymes and
hormones) for export
•  Like a “packaging center”
•  This was discovered by “Mr. Golgi”
who named it after himself.
Vesicle
•  Small membrane enclosed sac
•  Transports substances made by the
Golgi apparatus
•  Like a “delivery service”
•  Technically a special type of vacuole
•  Can’t tell by looking at it what it is…
unless it is right next to the Golgi.
Lysosomes
•  Membrane bound sacs of digestive
enzymes
–  Breaks down old organelles
–  Breaks down food items (in single celled
organism)
–  Cell induced death (embryonic or other)
•  Technically a special type of vesicle
•  Like a “cleaning crew” for the cell
Vacuoles
•  Membrane-bound sacs that hold
substances (general term)
•  Storage for
–  Food, water, wastes, etc.
•  Like a “storage cupboard”
•  Plants have one large vacuole for
storage AND support
•  Animal cells have many small vacuoles
(food vacuole, water vacuole, waste…)
Nucleus
•  Membrane bound organelle that
contains the genetic information
(DNA) of the cell
•  Concentrates parts and enzymes
needed for DNA replication and
transcription
•  Contains nucleolus
•  The “control center” or “Boss”
Nuclear Membrane
•  Double lipid bilayer that serves as a
physical barrier to separate the
contents of the nucleus from the
cytosol
•  A.K.A. “Nuclear Envelope”
•  Contains holes called “nuclear pores”
that allows the transports of certain
molecules
Nucleolus
•  Makes ribosomes (remember,
ribosomes make the proteins)
•  Like the “factory parts generator”, or
“HR department” that hires the
workers.
•  Sometimes referred to the “nucleus of
the nucleus” because it looks like a
blob inside the nucleus.
Mitochondria/ Mitrochondrion
•  Double membrane
•  Aerobic respiration
–  Makes energy (ATP)
–  Detoxifies O2
•  “Generator” or
“Power house”
because it’s the site
of ATP (battery)
production!
(#2 on this diagram)
Animal vs. Plant cells
•  All previous organelles have been in
both animal and plant cells
•  Now to the differences….
Centrioles
•  Cylindrical bundle of microtubules
•  Assists with cell division
•  Look like
churro sticks
•  Only in
animal cells
Cilia and/or Flagella
•  Cilia= shorter hair-like structures
–  Usually more numerous (all over)
•  Flagella= longer hair-like structures
(fewer)
•  Used for mobility (swimming)
•  Creates currents to sweep objects
towards or away from cell
•  SOME animal cells only, but NOT ALL
Cilia
Cilia
Organelles found in plants only
•  Cell wall
•  Plastids (chloroplast is the main
example)
Cell Wall
•  Made of cellulose in plants
–  (made of chitin in fungi)
* Different from Bacteria cell walls
•  Support for the cell (rigidity)
Plastids
3 different types of plastids:
•  Leucoplasts- store starch
•  Chromoplasts- store pigments
•  And the last one…
Chloroplasts
•  Organelle of photosynthesis: the
process by which plants convert
sunlight and water into sugar and
oxygen.
•  Much more different and more
complicated than the other plastidsnot just for storage
Something to remember
•  Cell diagrams are a “snapshot” of a
cell, frozen in time
•  Cells are living, changing, and some
of the organelles are MOVING.
(mitochondria are responsive, can
wiggle like their bacteria relatives.)
What an actual eukaryo/c cell looks like under a microscope! Can you iden/fy the structures on this image?