2. Mitochondria & Chloroplasts are special…
Not part of the endomembrane system because…
They both have 2 membranes separating their insides
from the cytosol
Have their own ribosomes
Contain small amounts of their own DNA to make
some of their own membrane proteins
Grow and reproduce independently of the cell
3. Mitochondria
Found in eukaryotic cells of plants,
animals, fungi, and protists
More active cells have more
mitochondria
Very small - ~ 1-10 microns
4. Structure of Mitochondria
2 membranes
Smooth outer membrane
Convoluted inner membrane
Folds called cristae
This membrane creates 2 spaces
inside the mitochondrion
Space between outer & inner
membrane = intermembrane space
Space inside inner membrane = matrix
Matrix has enzymes , DNA,
ribosomes
Lots of folds means lots of membrane
surface for cell respiration to occur
5. Chloroplasts
One of a family of plant organelles
called plastids
Amyloplast – store starch
Chromoplast – pigments that color
fruits and flowers
Chloroplast – contain the pigment
chlorophyll & enzymes for
photosynthesis
Very small ~ 2 microns
Found in green parts of plants
6. Structure of Chloroplasts
Double membrane with narrow
intermembrane space
Inside is second membrane system –
flattened discs called thylakoids
Stacks of thylakoids are called grana
Fluid inside grana called stroma
Stroma contains DNA, enzymes for
photosynthesis, ribosomes
7. Quick Think
Describe at least 2 things that
mitochondria and chloroplasts
have in common.
Explain why mitochondria and
chloroplasts are not part of the
endomembrane system.
8. Peroxisomes
Single membrane
Contain enzymes that transfer
hydrogen from other molecules
to oxygen to produce H2O2 as a
by-product.
Contains enzymes that then
break down H2O2 into water.
10. The Cytoskeleton
Cytoskeleton - a network of
fibers that runs through the
cell
Helps organize the inside of the
cell
Made up of 3 types of tubes:
Microtubules
Microfilaments
Intermediate filaments
12. Cytoskeleton Function
Aides in cell motility -2 types of motility:
Whole cell movement - the cytoskeleton
interacts with motor proteins to allow the cell
to move along fibers outside the cell
Movement of organelles and vesicles within
the cell - internal parts move along filaments
of cytoskeleton
Sperm around an
egg
14. Microtubules
Hollow
Made of a protein called tubulin
Give shape & support to cell
Allows for organelles to move
along them
Separate chromosomes during
cell division
Grow out of centrosomes in many
cells
15. Cilia & Flagella
Specialized arrangement of microtubules makes flagella &
cilia beat
Internal structure of both the same
Core of microtubules surrounded by plasma membrane
9 doublets of microtubules arranged in a ring
Wagon wheel proteins that connect each doublet
Motor proteins between each doublet
Whole thing anchored to cell at the basal body
16. Cilia & Flagella
Flagella on sperm
Cilia on cells in the throat move mucus along
Cilia in reproductive tract of females moves egg
toward uterus
Lots of unicellular eukaryotes use cilia and flagella
for movement in aquatic environments
18. Intermediate Filaments
Specialized for bearing tension
Made up of keratin proteins
More diverse than the other 2
More permanent than the other 2
Skin is dead cells full of keratin
proteins
Keep certain organelles, like
nucleus, locked in place
Maintain shape of cell, especially
odd shapes like neurons
19. Quick Think – complete the table
Main features Main functions
Microtubules Hollow,
thickest,
tubulin
support for cell,
organelles move
along it’s tracks,
cilia & flagella
Microfilaments Thinnest, solid
actin
Support cell
shape, muscle
contraction
Intermediate
filaments
In between
size, diverse
structure, more
permanent,
keratin
Lock certain
organelles in
place, maintain
irregular cell
shapes
20. Quick Think
There are many different cell types, even
within the same organism. Cells vary in
size, shape, structure, and function. This
is part of the diversity of life.
Which aspects of cells best reveal their
evolutionary unity?
What are some examples of specialized
cellular modifications?
