Date post: | 19-Jun-2015 |
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Mitochondria, Chloroplasts, Peroxisomes, & the Cytoskeleton
6.5-6.7
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 ribosomesContain small amounts of their own DNA to make
some of their own membrane proteinsGrow and reproduce independently of the cell
MitochondriaFound in eukaryotic cells of plants,
animals, fungi, and protistsMore active cells have more
mitochondriaVery small - ~ 1-10 microns
Structure of Mitochondria2 membranes
Smooth outer membraneConvoluted inner membrane
Folds called cristaeThis membrane creates 2 spaces
inside the mitochondrionSpace between outer & inner
membrane = intermembrane spaceSpace inside inner membrane = matrix
Matrix has enzymes , DNA, ribosomes
Lots of folds means lots of membrane surface for cell respiration to occur
ChloroplastsOne of a family of plant organelles
called plastidsAmyloplast – store starchChromoplast – pigments that color
fruits and flowersChloroplast – contain the pigment
chlorophyll & enzymes for photosynthesisVery small ~ 2 micronsFound in green parts of plants
Structure of ChloroplastsDouble membrane with narrow
intermembrane space Inside is second membrane system –
flattened discs called thylakoidsStacks of thylakoids are called granaFluid inside grana called stroma
Stroma contains DNA, enzymes for photosynthesis, ribosomes
Quick ThinkDescribe at least 2 things that
mitochondria and chloroplasts have in common.
Explain why mitochondria and chloroplasts are not part of the endomembrane system.
PeroxisomesSingle membraneContain 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.
PeroxisomesMany different functionsSome are used to break down fatty acidsThose in the liver detoxify alcohol
The CytoskeletonCytoskeleton - a network of
fibers that runs through the cellHelps organize the inside of the
cellMade up of 3 types of tubes:
MicrotubulesMicrofilamentsIntermediate filaments
Cytoskeleton Functions
Supports cellMaintains cell shape
(important for animal cells since no cell wall)
Can be dismantled and reformed quickly so cells can change shape
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
Cytoskeleton Structure
Microtubules - thickestMicrofilaments - thinnest (aka
actin filaments)Intermediate filaments - mid
sized
Microtubules
HollowMade of a protein called tubulinGive shape & support to cellAllows for organelles to move
along themSeparate chromosomes during
cell divisionGrow out of centrosomes in many
cells
Cilia & FlagellaSpecialized arrangement of microtubules makes flagella &
cilia beat Internal structure of both the same
Core of microtubules surrounded by plasma membrane9 doublets of microtubules arranged in a ringWagon wheel proteins that connect each doubletMotor proteins between each doubletWhole thing anchored to cell at the basal body
Cilia & Flagella Flagella on spermCilia on cells in the throat move mucus alongCilia in reproductive tract of females moves egg
toward uterusLots of unicellular eukaryotes use cilia and flagella
for movement in aquatic environments
Microfilaments (Actin Filaments)
SolidBuilt from a protein called actinHelp support cell’s shapeHave an important role in muscle
contraction
Intermediate FilamentsSpecialized for bearing tensionMade up of keratin proteinsMore diverse than the other 2More 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
Quick Think – complete the tableMain 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
Quick ThinkThere 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?