The Cell: The Cell: Mitochondria & Mitochondria &

Chloroplasts Chloroplasts

OverviewOverview Mitochondria & chloroplasts are the Mitochondria & chloroplasts are the

organelles that convert energy to organelles that convert energy to forms that cells can use for workforms that cells can use for work– mitochondriamitochondria::

from glucose to ATPfrom glucose to ATP– chloroplastschloroplasts::

from sunlight to ATP & from sunlight to ATP & carbohydratescarbohydrates ATP = active energyATP = active energy carbohydrates = stored energycarbohydrates = stored energy

ATP

+ATP

Mitochondria & Mitochondria & ChloroplastsChloroplasts

Important to see the similaritiesImportant to see the similarities– transform energytransform energy

generate ATPgenerate ATP

– double membranes = 2 membranesdouble membranes = 2 membranes– semi-autonomous organellessemi-autonomous organelles

move, change shape, dividemove, change shape, divide

– internal ribosomes, DNA & enzymesinternal ribosomes, DNA & enzymes

MitochondriaMitochondria FunctionFunction

– cellular respirationcellular respiration– generate ATP generate ATP

from breakdown of sugars, fats from breakdown of sugars, fats & other fuels & other fuels

in the presence of in the presence of oxygenoxygen– break down larger molecules into smaller to break down larger molecules into smaller to

generate energy = generate energy = catabolismcatabolism

– generate energy in presence of Ogenerate energy in presence of O22 = = aerobic aerobic respirationrespiration

MitochondriaMitochondria StructureStructure

– 2 membranes2 membranes smooth outer membrane smooth outer membrane highly folded inner membranehighly folded inner membrane

– the the cristaecristae

– fluid-filled space between 2 fluid-filled space between 2 membranesmembranes

– internal fluid-filled spaceinternal fluid-filled space mitochondrial matrixmitochondrial matrix DNA, ribosomes & enzymesDNA, ribosomes & enzymes

Why 2 membranes?

increase surface area for membrane-bound enzymes that synthesize ATP

MitochondriaMitochondria

Membrane-bound Membrane-bound EnzymesEnzymes

Dividing MitochondriaDividing MitochondriaWho else divides

like that?

What does this tell us about the evolution of eukaryotes?

MitochondriaMitochondria Almost all eukaryotic cells have Almost all eukaryotic cells have

mitochondriamitochondria– there may be 1 very large mitochondrion or there may be 1 very large mitochondrion or

100s to 1000s of individual mitochondria100s to 1000s of individual mitochondria– number of mitochondria is correlated with number of mitochondria is correlated with

aerobic metabolic activityaerobic metabolic activity more activity = more energy more activity = more energy

needed = more mitochondrianeeded = more mitochondriaWhat cells would have a lot of mitochondria?

active cells: • muscle cells • nerve cells

ChloroplastsChloroplasts Chloroplasts are Chloroplasts are plantplant organelles organelles

– class of plant structures = class of plant structures = plastidsplastids amyloplastsamyloplasts

– store starch in roots & tubersstore starch in roots & tubers chromoplastschromoplasts

– store pigments for fruits & flowersstore pigments for fruits & flowers chloroplastschloroplasts

– store chlorophyll & function store chlorophyll & function in photosynthesisin photosynthesis

– in leaves, other green in leaves, other green structures of plants & structures of plants & in eukaryotic algaein eukaryotic algae

ChloroplastsChloroplasts StructureStructure

– 2 membranes2 membranes outer membrane outer membrane inner membraneinner membrane

– internal fluid-filled space = internal fluid-filled space = stromastroma DNA, ribosomes & enzymesDNA, ribosomes & enzymes thylakoidsthylakoids = membranous sacs where ATP is made = membranous sacs where ATP is made granagrana = stacks of thylakoids = stacks of thylakoids

Why internal sac membranes?

increase surface area for membrane-bound enzymes that synthesize ATP

Membrane-bound Membrane-bound EnzymesEnzymes

ChloroplastsChloroplasts FunctionFunction

– photosynthesisphotosynthesis – generate ATP & synthesize sugarsgenerate ATP & synthesize sugars

transform solar energy into chemical energytransform solar energy into chemical energy produce sugars from COproduce sugars from CO22 & H & H22OO

Semi-autonomousSemi-autonomous moving, changing shape & dividingmoving, changing shape & dividing can reproduce by pinching in twocan reproduce by pinching in two

Who else divides like that?

bacteria!

Chloroplasts Chloroplasts Why are chloroplasts green?Why are chloroplasts green?

Mitochondria & chloroplasts Mitochondria & chloroplasts are differentare different

Organelles not part of Organelles not part of endomembraneendomembrane systemsystem

Grow & reproduce Grow & reproduce – semi-autonomous organellessemi-autonomous organelles

Proteins primarily from free ribosomes Proteins primarily from free ribosomes in cytosol & a few from their own in cytosol & a few from their own ribosomesribosomes

Own circular chromosome Own circular chromosome – directs synthesis of proteins produced by directs synthesis of proteins produced by

own internal ribosomesown internal ribosomesWho else has a circular chromosome no bound within a nucleus?

bacteria

Endosymbiosis theoryEndosymbiosis theory Mitochondria & chloroplasts were Mitochondria & chloroplasts were

once free living bacteriaonce free living bacteria– engulfed by ancestral eukaryoteengulfed by ancestral eukaryote

EndosymbiontEndosymbiont – cell that lives within another cell (host)cell that lives within another cell (host)

as a partnershipas a partnership evolutionary advantage evolutionary advantage

for bothfor both– one supplies energyone supplies energy– the other supplies raw materials the other supplies raw materials

& protection& protectionLynn MargulisU of M, Amherst

Endosymbiosis theoryEndosymbiosis theoryEvolution of eukaryotes