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Tour of the Cell 1
Animation
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Endosymbiosis theory
 Origin of Eukarayotic cells
 Lynn Margulis
1.
1981 | ??
Circular DNA
1. Mito, Chloro and Prokarayotes
2.
Double Membrane
1. Mito, Chloro took on membrane of hosts
3.
4.
Own Ribosomes
Same Size
1. Mito.chloro are same size as Bacteria
Mito  Purple Bacteria // Chloro photosynthetic bacteria
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Endosymbiosis theory
Evolution of eukaryotes
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Why organelles? Why?
 Specialized structures

specialized functions
mitochondria
 cilia or flagella for locomotion
 Containers


partition cell into compartments
create different local environments
chloroplast
 separate pH, or concentration of materials

distinct & incompatible functions
 lysosome & its digestive enzymes
 Membranes as sites for chemical reactions


unique combinations of lipids & proteins
embedded enzymes & reaction centers
Golgi
 chloroplasts & mitochondria
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ER
Cells gotta work to live!
 What jobs do cells have to do?

make proteins
 proteins control every
cell function

make energy
 for daily life
 for growth

make more cells
 growth
 repair
 renewal
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1. Mitochondria
 Function
 Converts glucose to ATP in the presence




of Oxygen
Double membrane system from
endosymbiosis
3-10 DNA loops
Contains self produced Ribosomes
Inner membrane – Cristae

Studded w/ ATP synthase
 Matrix – Krebs cycle – part of cellular
respiration
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Mitochondria
 Reproduces on its own by
binary fission

Grow and then divide
 mt DNA

Mitochondrial DNA
 37 genes
 Slow to mutate
 Can show clear evolutionary ancestral lineages
(phylogenic) through the maternal line

Mitochondrial Eves
 Based on mt DNA evidence, a small group of
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mothers “began” the modern human race in
Africa - 200,000 years ago
Mitochondria
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Dividing Mitochondria
Who else divides
like that?
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What does this tell us about
the evolution of eukaryotes?
Mitochondria - Extra
 Almost all eukaryotic cells have mitochondria


there may be 1 very large mitochondrion or
100s to 1000s of individual mitochondria
number of mitochondria is correlated with
aerobic metabolic activity
 more activity = more energy
needed = more mitochondria
What cells would
have a lot of
mitochondria?
active cells:
• muscle cells
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• nerve cells
Mitochondria are everywhere!!
animal cells
plant cells
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2) Plastids
 Chloroplasts are plant organelles

class of plant structures = plastids
A. amyloplasts
 store starch in roots & tubers
B. chromoplasts
 store pigments for fruits & flowers
C. chloroplasts
 store chlorophyll & function
in photosynthesis
 in leaves, other green
structures of plants &
in eukaryotic algae
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Chloroplasts
C.
Chloroplasts
(2 membranes)
A. Thylakoids
A. membranes containing chlorophyll a
photosynthetic pigment
B. Responsible for the light reactions
B. Stroma
A. Fluid in which glucose is produced
B. Responsible for the dark reactions (calvin
cycle)
Why internal
sac
membranes?
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increase surface area for
membrane-bound enzymes
that synthesize ATP
Chloroplasts
Why are chloroplasts green?
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DNA
3. Nucleus
chromosome
 Double membrane structure w/ nuclear
pores (nuclear envelope)
histone protein
 Contains the DNA – the genome of the
eukaryotic species
 Site of Replication and Transcription
nuclear
pores
What kind of
molecules need to
pass through?
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nuclear
pore
nucleolus
nuclear envelope
1
nuclear
membrane
production of mRNA
from DNA in nucleus
DNA
Nucleus
mRNA
2
nuclear pore
mRNA travels from
nucleus to ribosome
in cytoplasm through
nuclear pore
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small
ribosomal
subunit
mRNA
large
ribosomal
subunit
cytoplasm
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How is DNA Packaged
DNA 
Gene

Chromatid(n)
sequences of nucleotides
that codes for a protein
 Nucleosome

DNA wound around histone proteins
 Chromatid – packaged/wound DNA
 Chromatin

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Unbound/ loose DNA
Start at 9:15
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Nucleolus
 Function

ribosome production
 build ribosome subunits from rRNA & proteins
 exit through nuclear pores to cytoplasm &
combine to form functional ribosomes
large subunit
small
subunit
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rRNA &
proteins
ribosome
nucleolus
Hetereochromatin
 “Junk DNA”
 Unreadable, not useful
 Tightly wound around histones
 Most genes inactive (methylated)
 Involved in gene regulation
 Found in centromeres and telomeres,
barr body (shut down second X)
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Euchromatin
 Readable DNA
 Located near nuclear centers and near



pores
Loose (useful)
Most genes are active
Involved in transcription
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large
subunit
4. (kinda) Ribosomes
 Site of protein synthesis
 Complex of rRNA and


small
subunit
protein
Constructed in
nucleolus
Ribosomes
Found in the cytosol and Rough
ER
attached to ER (rough)
Smooth
ER
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0.08mm
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The Endomembrane System
1.
2.
3.
4.
5.
6.
7.
8.
Nuclear Envelope*
Rough Endoplasmic Reticulum (RER)
Smooth Endoplasmic Reticulum (SER)
Golgi Apparatus
Lysosomes
Peroxisomes
Vacuoles
Plasma (cell) membrane*
•
•
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*start and end of endomembrane – not part
of system
All composed of phospholipid bilayer
Vesicals
 – membrane bound structures that
bring the product from one membrane
to another.
__________________________________
Lumen
Inside of something
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2) Rough Endoplasmic Reticulum
 Transport systems attached to nuclear
envelope / studded with ribosomes
(rough)
 Location of most protein synthesis
Which cells
 Extensive membranous network
have of
lot tubules
of
rough ER?
and sacs (cisternae)
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Types of ER
rough
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smooth
3. Smooth ER function
 ER w/o ribosomes
 Responsible for lipid production,


phospholipids and vitamins
Participates in carbohydrate metabolism
(glycogen  glucose)
Detoxification of drugs and poisons.
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Membrane Factory - extra
 Build new
membrane

synthesize
phospholipids
 builds membranes

ER membrane
expands
 bud off & transfer
to other parts of
cell that need
membranes
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Synthesizing proteins
cisternal
space
polypeptide
signal
sequence
ribosome
ribosome
mRNA
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membrane of
endoplasmic reticulum
cytoplasm
4. Golgi Apparatus
 Series of flattened sacs whose
function is to modify and package
proteins into their proper configuration
 Each sac is called a cisternae
 Cis face – receives vesicles
secretory
vesicles
Whichcells
Trans
face
–
produces
vesicles
have lots
of Golgi?
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transport vesicles
Golgi Apparatus
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Vesicle transport
protein
vesicle
budding
from rough
ER
ribosome
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migrating
transport
vesicle
fusion
of vesicle
with Golgi
apparatus
endoplasmic
reticulum
nucleus
protein
on its way!
DNA
RNA
vesicle
TO:
TO:
TO:
vesicle
ribosomes
TO:
finished
protein
protein
Golgi
apparatus
Making Proteins
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Putting it together…
nucleus
nuclear pore
Making proteins
cell
membrane
protein secreted
rough ER
ribosome
vesicle
proteins
smooth ER
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transport
vesicle
cytoplasm
Golgi
apparatus
5. Lysosomes
 Function

little “stomach” of the cell
 digests macromolecules

“clean up crew” of the cell
 cleans up broken down
organelles
 Structure

vesicles of digestive
enzymes
synthesized by rER,
transferred
to Golgi
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only in
animal cells
Where
old organelles
go to die!
1960 | 1974
Lysosomes
white blood cells attack
& destroy invaders =
digest them in
lysosomes
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1974 Nobel prize: Christian de Duve
Lysosomes discovery in 1960s
Cellular digestion
 Lysosomes fuse with food vacuoles

polymers
digested into
monomers
 pass to cytosol
to become
nutrients of
cell
vacuole
 lyso– = breaking things apart
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 –some
= body
6. Peroxisomes
 Vesicle that contains catalase –

Catalase does what?

H2O2  H2O + O2
 Found in high numbers in liver cells
Toxins are often broken
down into peroxide

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7. Vacuoles & vesicles
 Function

little “transfer ships”
 Food vacuoles
 phagocytosis, fuse with lysosomes
 Contractile vacuoles
 in freshwater protists, pump excess H2O
out of cell
 Central vacuoles
 in many mature plant cells
contains H2O
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Cytoskeleton
 Helps maintain/change the
shape of the cell
 “Dynamic” skeleton  ameobas
 Interacts w/ motor proteins (kinesin) to
transport vesicles
 Motility
the ability to move
spontaneously and
actively, consuming
energy in the process
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
Cytoskeleton
 actin
 microtubule
 nuclei
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Types – 1) Microfilaments
 Made of actin –

Actin is a globular protein
 Support for the cell membrane
 Building actin can move a cell in a



particular direction
Amoeboid movement
Muscle movement (actin and myosin)
Cyclosis (cytoplasmic streaming)

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“things” moving along the edge of the cell
Table 6-1b
10 µm
Actin subunit
7 nm
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Fig. 6-27
Muscle cell
Actin filament
Myosin filament
Myosin arm
(a) Myosin motors in muscle cell contraction
Cortex (outer cytoplasm):
gel with actin network
Inner cytoplasm: sol
with actin subunits
Extending
pseudopodium
(b) Amoeboid movement
Nonmoving cortical
cytoplasm (gel)
Chloroplast
Streaming
cytoplasm
(sol)
Vacuole
Parallel actin
filaments
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(c) Cytoplasmic streaming in plant cells
Cell wall
2) Microtubules
 Constructed of tubulin dimers
(proteins)
 Eminate from centrosomes

Area where centrioles are located
 Tracks for organelle and vesicle


movement (Kinesin)
Movement of chromosomes during
mitosis (spindles)
Cilia and flagella are constructed of
microtubules in the 9 +2 array
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Centrioles (Extra)
 Cell division

in animal cells, pair of centrioles
organize microtubules
 spindle fibers

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guide chromosomes in mitosis
Fig. 6-20
Microtub
ule
0.25
µm
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Microfilame
nts
Fig. 6-21
ATP
Vesicle
Receptor for
motor protein
Motor protein Microtubule
(ATP powered) of cytoskeleton
(a)
Microtubule
(b)
Vesicles
0.25 µm
Table 6-1a
10
µm
Column
of tubulin
dimers
25 nm

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
Tubulin dimer
Fig. 6-24
Outer microtubule
doublet
0.1 µm
Dynein proteins
Central
microtubule
Radial
spoke
Protein crosslinking outer
doublets
Microtubules
Plasma
membrane
(b) Cross section of
cilium
Basal body
0.5 µm
(a)
Longitudinal
section of cilium
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0.1 µm
Triplet
(c) Cross section of basal body
Plasma
membrane
 Cilia
Help move particles along the throat
 Help move the egg from the ovary to
uterus

 Flagellum

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Sperm tail
Fig. 6-22
Centroso
me
Microtub
ule
Centriole
s
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0.25
µm
Longitudinal Microtubul Cross section
section of one
of the other
es
Fig. 6-23
Direction of swimming
(a) Motion of flagella
5 µm
Direction of organism’s movement
Power stroke Recovery stroke
(b) Motion of cilia
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15 µm
Table 6-1c
5 µm
3) Intermediate filaments
Keratin proteins
Fibrous subunit (keratins
coiled together)
8–12 nm
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3) Intermediate filaments
 Constructed in Keratin fibers (hair)
 Fix organelle position
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Extracellular Structures
 1) The cell wall



Secreted by the cell
Fully permeable
Osmoregulation – protects cell from bursting
 A) Plant cell wall


Made of cellulose
Aggregation of golgi produced vesicles filled
w/ cellulose (cellulose synthase) along the
central plate
 B) Fungi cell wall


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Made of chitin
Animal cells – they do not photosynthesize!!!!!
2) The extracellular matrix
 Proteins secreted from an animal cell
that interact with glycoproteins on the
cell membrane to “glue” multiple cells
together

Collagen is most common protein
 This is how cells become tissue
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Fig. 6-30a
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Fibronectin
Integrins
Plasma
membrane
Microfilaments
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CYTOPLASM
3) The intercellular junctions
 Plasmodesmata (P)

A channel system through a cell wall which
joins the cell membrane of adjacent cells
 Gap Junctions (A)




Made of proteins
Do not have to go through cell walls (animal
cells)
Channel from one cell to another
Joins 2 cells allowing for the sharing of info
and materials
 Tight Junctions


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Sewing cell membrane so nothing can get
through
No intercellular space
Fig. 6-31
Cell
walls
Interi
or of
cell
Interi
or of
cell
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0.5
µm
Plasmodes
mata
Plasma
membranes
Fig. 6-32
Tight junction
Tight junctions prevent
fluid from moving
across a layer of cells
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
Gap
junctions
Space
between
cells
Plasma membranes
of adjacent cells
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Desmosome
1 µm
Extracellular
matrix
Gap junction
0.1 µm
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Any Questions!!
Inside life of Cell Explained
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2007-2008