Eukaryotic cell structure
The Cell factory
 Organelles
 Highly specialized structures within the cell
 Little organs
 2 major divisions of the eukaryotic cell
 Nucleus
 The “brain”
 DNA
 Cytoplasm
 Portion outside the nucleus but inside the cell membrane
2 types of Eukaryotic cells
 Plant cells
 Animal cells
 What are the differences? (write them down!!!)
Cell Membrane
 What does it do for cell?
 Controls what goes in and out
 Regulates molecules moving from one liquid side of the
cell to the other liquid side of the cell
 Protects
 Supports
Cell Membrane
 Lipid bilayer
 What are lipids?
 What does bi- mean?
 What’s a layer?
 A cell membrane is made of two
layers of lipid molecules
Cell membrane
 Phospholipids bilayer
 Made of a negatively charged
phosphate “head”
 PO43water because the phosphate is
 Attracts
charged (-)
is a polar , slightly positive ends
 Water
and slightly negative ends
 Attached to the phosphate
group are 2 fatty acid chains
 Hydrophobic= don’t like water
 So the inside of the cell
membrane doesn’t let water in
but the outside allows cells to be
dissolved in aqueous
environments
Plasma/Cell Membrane
 Phospholipid bilayer
 Hydrophilic
 Hydophobic
 Fluid Mosaic Model
 Why?
 Controls exchange
of materials
between cell and its
environment
Other things in the
membrane…
 Proteins embedded in
lipid bilayer
 Carbohydrates
attached to proteins
 So many different
molecules in
membrane, we call it a
“mosaic” of different
molecules
What is a Nucleus?
 Plural: nuclei
 Large, membrane enclosed structure that
contains the cell’s genetic material in the form
of DNA
 What is a membrane?
 A thin layer of material that serves as a covering or
lining
Nucleus
 Brain of the cell
 Office of the factory
 Contains nearly all the cell’s DNA and with
it the coded instructions for making
PROTEINS and other important molecules
Nuclear envelope
 Surrounds nucleus
 Made of 2 membranes
 Dotted with thousands of nuclear pores
 How do we get messages, instructions and
blueprints out of the office?
 Allow material to move in and out of nucleus by
using “little runners” such as proteins, RNA and
other molecules
Inside the nucleus
we see…
 Contain a granular material called…
 CHROMATIN
 Chromatin= DNA + protein
 Usually spread out in nucleus
 During cell division, chromatin clumps together or
condenses…we call this….
 CHROMOSOMES
Chromosomes
 Condensed structures that contain genetic
information (DNA) that is passed on from one
generation to the next
Nucleolus
 Small dense
region inside the
nucleus
 Function:
assembly of
ribosomes
begin…
Ribosomes
 Most important function of cell is…
 Making proteins
 Proteins regulate a zillion different things
 Like…
 Proteins are assembled ON Ribosomes
 Consists of 2 parts:
 Large subunit
 Small subunit
 Found:
 In Cytoplasm
 On Rough ER
 In nucleus
 Function:
 hold mRNA in place while tRNA brings
over specific amino acids; makes a
polypeptide chain
 Site of protein synthesis
Endoplasmic reticulum (ER)
 Internal membrane system
 site where the lipid components of the
cell membrane are assembled, along
with proteins and other materials
exported from the cell
 2 types
 Smooth ER
 Rough ER
Rough ER
 Involved in protein making
(synthesis)
 So what are we going to see
on it?
 ribosomes
 Once a protein is made, it
leaves the ribosome and
goes into the Rough ER
 The rough ER then modifies
the protein
 All proteins that are exported
by the cell are made on the
RER
 Membrane proteins are made
on the RER too
Smooth ER
 NO ribosomes on it
 Looks smooth
 Contains collections of ENZYMES that have
specialized tasks
 What do enzymes do?
 Tasks include:
 Synthesis of membrane lipids
 Detoxification of drugs
 Liver cells
 Big in detox therefore….what do u think liver cells have a lot of?
Golgi Apparatus
 Discovered by Italian scientist Camillo
Golgi
 Once proteins are done being
“modified” in the RER, they move onto
the Golgi apparatus
 Looks like a stack of pancakes
 Function: modify, sort, and package
proteins and other materials from the
ER for STORAGE or SECRETION
outside the cell
 Proteins are “shipped” to final destination
 They are the CUSTOMIZATION SHOP
 Finishing touches on proteins before they
leave factory
Endomembrane System & Protein
Synthesis
1.
2.
3.
4.
DNA in nucleus gives message to mRNA
mRNA leave thru nuclear pore into cytoplasm
Ribsome “catches” mRNA
tRNA come over and start adding amino acids together making
polypeptide chain
5. Polypeptide chain either functions immediately or goes onto next
step
6. Ribosome deposits polypeptide chain into lumen of the RER
7. Polypeptide chain is modified (2* and 3* structure)
8. Functioning protein either stays and works in RER or…
9. Vesicle buds off RER and transports it to Golgi Apparatus
10. Protein is further modified in GA and leaves in a vesicle (either
secretory or peroxisome or membrane)
Lysosomes
 (Lie-so-soh-mz)
 The factory’s clean-up crew
 It’s an Organelle filled with
enzymes
 Function: Digestion (break
down) of lipids,
carbohydrates, and proteins
into smaller molecules that
can be used by the cell
 Also digest organelles that
have outlived their
usefulness
What do you think happens if
lysosomes malfunction?
 A bunch of “junk” build up in the
cell…why?
 Is this good?
 Many human diseases result from
malfunction of lysosome
 Tay-Sachs disease
 DNA does not make the enzyme
hexoaminidase A that breaks
down lipids in nerve cells
 Build up of lipids in nerve cells
causes those cells to stop
working
 Noticeable 3-6 months after birth,
child lives to be about 4-5 years
old
Vacuoles
The factory’s storage place
Only in certain cells
Sac-like organelles
Function: stores material such as water,
salts, proteins, and carbohydrates
 Plant cells have a single, large central
vacuole

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
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 Pressure of central vacuole allows plants to
support heavy structures