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Plan C Pick a problem Pick some plants to study Design some experiments See where they lead us. Endomembrane system Organelles derived from the ER 1) ER 2) Golgi 3) Vacuoles 4) Plasma Membrane 5) Nuclear Envelope 6) Endosomes 7) Oleosomes. VACUOLES Vacuoles are subdivided:

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Plan C

Pick a problem

Pick some plants to study

Design some experiments

See where they lead us


Endomembrane system

Organelles derived from the ER

1) ER

2) Golgi

3) Vacuoles

4) Plasma

Membrane

5) Nuclear

Envelope

6) Endosomes

7) Oleosomes


VACUOLES

Vacuoles are subdivided:

lytic vacuoles are distinct

from storage vacuoles!


  • Endomembrane System

  • Oleosomes: oil storage bodies derived from SER

  • Surrounded by lipid monolayer!

    • filled with lipids: no internal hydrophobic effect!


  • endosymbionts

  • derived by division of preexisting organelles

  • no vesicle transport

  • Proteins & lipids are not glycosylated


  • endosymbionts

  • derived by division of preexisting organelles

  • little exchange of membranes with other organelles

  • 1) Peroxisomes (microbodies)




  • Peroxisomes

  • Fn:

    • destroy H2O2, other O2-related poisons

    • change fat to CH2O (glyoxysomes)


  • Peroxisomes

  • Fns:

    • destroy H2O2, other

      O2-related poisons

    • change fat to CH2O

      (glyoxysomes)

    • Detoxify & recycle

      photorespiration products


  • Peroxisomes

  • Fn:

    • destroy H2O2, other O2-related poisons

    • change fat to CH2O (glyoxysomes)

    • Detoxify & recycle photorespiration products

    • Destroy EtOH (made in anaerobic roots)


  • Peroxisomes

  • ER can make peroxisomes under special circumstances!

  • e.g. peroxisome-less mutants can restore peroxisomes when the wild-type gene is restored


endosymbionts

1) Peroxisomes (microbodies)

2) Mitochondria



Mitochondria

2 membranes

Smooth OM


Mitochondria

2 membranes

Smooth OM

IM folds into cristae


  • Mitochondria

    • -> 4 compartments

    • 1) OM

    • 2) intermembrane space

    • 3) IM

    • 4) matrix



  • Mitochondria

    • matrix contains DNA, RNA and ribosomes

    • Genomes vary from 100,000 to 2,500,000 bp, but only 40-43 genes


  • Mitochondria

    • matrix contains DNA, RNA and ribosomes

    • Genomes vary from 100,000 to 2,500,000 bp, but only 40-43 genes

    • Reproduce by fission


  • Mitochondria

    • matrix contains DNA, RNA and ribosomes

    • Genomes vary from 100,000 to 2,500,000 bp, but only 40-43 genes

    • Reproduce by fission

    • IM is 25% cardiolipin, a bacterial phospholipid


  • Mitochondria

    • Genomes vary from 100,000 to 2,500,000 bp, but only 40-43 genes

    • Reproduce by fission

    • IM is 25% cardiolipin, a bacterial phospholipid

    • Genes most related to Rhodobacteria


  • Mitochondria

    • Fn : cellular respiration

    • -> oxidizing food & supplying energy to cell

    • Also make many important biochemicals


  • Mitochondria

    • Fn : cellular respiration

    • -> oxidizing food & supplying energy to cell

    • Also make important biochemicals & help recycle PR products



  • Plastids

    • Chloroplasts do photosynthesis

    • Amyloplasts store starch

    • Chromoplasts store pigments

    • Leucoplasts are found in roots


  • Chloroplasts

    • Bounded by 2 membranes

  • 1) outer envelope

  • 2) inner envelope


  • Chloroplasts

  • Interior = stroma

  • Contains thylakoids

  • membranes where light

  • rxns of photosynthesis occur

  • mainly galactolipids


  • Chloroplasts

  • Interior = stroma

  • Contains thylakoids

  • membranes where light rxns of photosynthesis occur

  • mainly galactolipids

  • Contain DNA, RNA, ribosomes


Chloroplasts

Contain DNA, RNA, ribosomes

120,000-160,000 bp, ~ 100 genes


Chloroplasts

Contain DNA, RNA, ribosomes

120,000-160,000 bp, ~ 100 genes

Closest relatives = cyanobacteria


Chloroplasts

Contain DNA, RNA, ribosomes

120,000-160,000 bp, ~ 100 genes

Closest relatives = cyanobacteria

Divide by fission


Chloroplasts

Contain DNA, RNA, ribosomes

120,000-160,000 bp, ~ 100 genes

Closest relatives = cyanobacteria

Divide by fission

Fns: Photosynthesis


Chloroplasts

Fns: Photosynthesis & starch synth

Photoassimilation of N & S


Chloroplasts

Fns: Photosynthesis & starch synth

Photoassimilation of N & S

Fatty acid & some lipid synth


Chloroplasts

Fns: Photosynthesis & starch synth

Photoassimilation of N & S

Fatty acid & some lipid synth

Synth of ABA, GA, many other biochem


  • Chloroplasts & Mitochondria

    • Contain eubacterial DNA, RNA, ribosomes

    • Inner membranes have bacterial lipids

    • Divide by fission

    • Provide best support for endosymbiosis


Endosymbiosis theory (Margulis)

Archaebacteria ate eubacteria & converted them to symbionts


Endosymbiosis theory (Margulis)

Archaebacteria ate

eubacteria &

converted them

to symbionts


Endosymbiosis theory (Margulis)

Archaebacteria ate

eubacteria &

converted them

to symbionts


  • cytoskeleton

  • network of proteins which give cells their shape

    • also responsible for shape of plant cells because guide cell wall formation

    • left intact by detergents that extract rest of cell


Cytoskeleton

Actin fibers (microfilaments)

~7 nm diameter

Form 2 chains of polar actin subunits arranged in a double helix


  • Actin fibers

  • polar subunits arranged in a double helix

  • Add to + end

  • Fall off - end

  • Fn = movement


Actin fibers

Very conserved in evolution

Fn = motility

Often with myosin


Actin fibers

Very conserved in evolution

Fn = motility

Often with myosin: responsible for cytoplasmic streaming


Actin fibers

Very conserved in evolution

Fn = motility

Often with myosin: responsible for cytoplasmic streaming,

Pollen tube growth & movement through plasmodesmata


Actin fibers

Often with myosin: responsible for cytoplasmic streaming,

Pollen tube growth & movement through plasmodesmata


Intermediate filaments

Protein fibers 8-12 nm dia (between MFs & MTs)

form similar looking filaments

Conserved central, rod-shaped -helical domain


Intermediate filaments

2 monomers form dimers with parallel subunits

Dimers form

tetramers

aligned in

opposite

orientations

& staggered


Intermediate filaments

2 monomers form dimers with parallel subunits

Dimers form

tetramers

Tetramers

form IF


Intermediate filaments

2 monomers form dimers with parallel subunits

Dimers form

tetramers

Tetramers

form IF

Plants have several:

Fn unclear


  • Microtubules

  • Hollow, cylindrical; found in most eukaryotes

    • outer diameter - 24 nm

    • wall thickness - ~ 5 nm

    • Made of 13 longitudinal rows

    • of protofilaments


Microtubules

Made of abtubulin subunits

polymerize to form protofilaments (PF)

PF form sheets

Sheets form

microtubules


  • Protofilaments are polar

  • -tubulin @ - end

  • -tubulin @ + end

  • all in single MT have same polarity


  • Microtubules

    In constant flux

    polymerizing &depolymerizing

    Add to  (+)

    Fall off  (-)


    Microtubules

    Control growth by controlling

    rates of assembly &disassembly

    because these are distinct processes

    can be controlled independently!

    ColchicinemakesMTs disassemble

    Taxol prevents disassembly


    Microtubules

    Control growth by controlling rates of assembly &disassembly

    Are constantly rearranging inside plant cells!


    • Microtubules

    • Control growth by controlling rates of assembly &disassembly

    • Are constantly rearranging inside plant cells!

      • during mitosis & cytokinesis


    • Microtubules

    • Control growth by controlling rates of assembly &disassembly

    • Are constantly rearranging inside plant cells!

      • during mitosis & cytokinesis

      • Guide formation of cell plate & of walls in interphase


    µT Assembly

    µTs always emerge from Microtubule-Organizing Centers (MTOC)


    µT Assembly

    µTs always emerge from Microtubule-Organizing Centers (MTOC) patches of material at outer nuclear envelope


    • Microtubules

    • MAPs (Microtubule Associated Proteins) may:

      • stabilize tubules

      • alter rates of

      • assembly/disassembly

      • crosslink adjacent

      • tubules

      • link cargo


    2 classes of molecular motors

    1) Kinesins move cargo to µT plus end

    2) Dyneins move cargo tominus end

    “Walk” hand-over-hand towards chosen end


    µT functions

    Give cells shape by guiding cellulose synth


    µT functions

    Give cells shape by guiding cellulose synth

    Anchor organelles


    µT functions

    Give cells shape by guiding cellulose synth

    Anchor organelles

    Intracellular motility


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