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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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Presentation Transcript
slide1

Plan C

Pick a problem

Pick some plants to study

Design some experiments

See where they lead us

slide2

Endomembrane system

Organelles derived from the ER

1) ER

2) Golgi

3) Vacuoles

4) Plasma

Membrane

5) Nuclear

Envelope

6) Endosomes

7) Oleosomes

slide3

VACUOLES

Vacuoles are subdivided:

lytic vacuoles are distinct

from storage vacuoles!

slide4

Endomembrane System

  • Oleosomes: oil storage bodies derived from SER
  • Surrounded by lipid monolayer!
    • filled with lipids: no internal hydrophobic effect!
slide5

endosymbionts

  • derived by division of preexisting organelles
  • no vesicle transport
  • Proteins & lipids are not glycosylated
slide6

endosymbionts

  • derived by division of preexisting organelles
  • little exchange of membranes with other organelles
  • 1) Peroxisomes (microbodies)
slide8

Peroxisomes (microbodies)

  • found in (nearly) all eukaryotes
  • 1 membrane
  • Fn:
    • 1) destroy H2O2, other O2-related poisons
slide9

Peroxisomes

  • Fn:
    • destroy H2O2, other O2-related poisons
    • change fat to CH2O (glyoxysomes)
slide10

Peroxisomes

  • Fns:
    • destroy H2O2, other

O2-related poisons

    • change fat to CH2O

(glyoxysomes)

    • Detoxify & recycle

photorespiration products

slide11

Peroxisomes

  • Fn:
    • destroy H2O2, other O2-related poisons
    • change fat to CH2O (glyoxysomes)
    • Detoxify & recycle photorespiration products
    • Destroy EtOH (made in anaerobic roots)
slide12

Peroxisomes

  • ER can make peroxisomes under special circumstances!
  • e.g. peroxisome-less mutants can restore peroxisomes when the wild-type gene is restored
slide13

endosymbionts

1) Peroxisomes (microbodies)

2) Mitochondria

slide14

Mitochondria

    • Bounded by 2 membranes
slide15

Mitochondria

2 membranes

Smooth OM

slide16

Mitochondria

2 membranes

Smooth OM

IM folds into cristae

slide17

Mitochondria

    • -> 4 compartments
    • 1) OM
    • 2) intermembrane space
    • 3) IM
    • 4) matrix
slide18

Mitochondria

    • matrix contains DNA, RNA and ribosomes
slide19

Mitochondria

    • matrix contains DNA, RNA and ribosomes
    • Genomes vary from 100,000 to 2,500,000 bp, but only 40-43 genes
slide20

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
slide21

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
slide22

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
slide23

Mitochondria

    • Fn : cellular respiration
    • -> oxidizing food & supplying energy to cell
    • Also make many important biochemicals
slide24

Mitochondria

    • Fn : cellular respiration
    • -> oxidizing food & supplying energy to cell
    • Also make important biochemicals & help recycle PR products
slide25

endosymbionts

    • Peroxisomes
    • Mitochondria
    • 3) Plastids
slide26

Plastids

    • Chloroplasts do photosynthesis
    • Amyloplasts store starch
    • Chromoplasts store pigments
    • Leucoplasts are found in roots
slide27

Chloroplasts

    • Bounded by 2 membranes
  • 1) outer envelope
  • 2) inner envelope
slide28

Chloroplasts

  • Interior = stroma
  • Contains thylakoids
  • membranes where light
  • rxns of photosynthesis occur
  • mainly galactolipids
slide29

Chloroplasts

  • Interior = stroma
  • Contains thylakoids
  • membranes where light rxns of photosynthesis occur
  • mainly galactolipids
  • Contain DNA, RNA, ribosomes
slide30

Chloroplasts

Contain DNA, RNA, ribosomes

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

slide31

Chloroplasts

Contain DNA, RNA, ribosomes

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

Closest relatives = cyanobacteria

slide32

Chloroplasts

Contain DNA, RNA, ribosomes

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

Closest relatives = cyanobacteria

Divide by fission

slide33

Chloroplasts

Contain DNA, RNA, ribosomes

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

Closest relatives = cyanobacteria

Divide by fission

Fns: Photosynthesis

slide34

Chloroplasts

Fns: Photosynthesis & starch synth

Photoassimilation of N & S

slide35

Chloroplasts

Fns: Photosynthesis & starch synth

Photoassimilation of N & S

Fatty acid & some lipid synth

slide36

Chloroplasts

Fns: Photosynthesis & starch synth

Photoassimilation of N & S

Fatty acid & some lipid synth

Synth of ABA, GA, many other biochem

slide37

Chloroplasts & Mitochondria

    • Contain eubacterial DNA, RNA, ribosomes
    • Inner membranes have bacterial lipids
    • Divide by fission
    • Provide best support for endosymbiosis
slide38

Endosymbiosis theory (Margulis)

Archaebacteria ate eubacteria & converted them to symbionts

slide39

Endosymbiosis theory (Margulis)

Archaebacteria ate

eubacteria &

converted them

to symbionts

slide40

Endosymbiosis theory (Margulis)

Archaebacteria ate

eubacteria &

converted them

to symbionts

slide41

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
slide42

Cytoskeleton

Actin fibers (microfilaments)

~7 nm diameter

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

slide43

Actin fibers

  • polar subunits arranged in a double helix
  • Add to + end
  • Fall off - end
  • Fn = movement
slide44

Actin fibers

Very conserved in evolution

Fn = motility

Often with myosin

slide45

Actin fibers

Very conserved in evolution

Fn = motility

Often with myosin: responsible for cytoplasmic streaming

slide46

Actin fibers

Very conserved in evolution

Fn = motility

Often with myosin: responsible for cytoplasmic streaming,

Pollen tube growth & movement through plasmodesmata

slide47

Actin fibers

Often with myosin: responsible for cytoplasmic streaming,

Pollen tube growth & movement through plasmodesmata

slide48

Intermediate filaments

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

form similar looking filaments

Conserved central, rod-shaped -helical domain

slide49

Intermediate filaments

2 monomers form dimers with parallel subunits

Dimers form

tetramers

aligned in

opposite

orientations

& staggered

slide50

Intermediate filaments

2 monomers form dimers with parallel subunits

Dimers form

tetramers

Tetramers

form IF

slide51

Intermediate filaments

2 monomers form dimers with parallel subunits

Dimers form

tetramers

Tetramers

form IF

Plants have several:

Fn unclear

slide52

Microtubules

  • Hollow, cylindrical; found in most eukaryotes
    • outer diameter - 24 nm
    • wall thickness - ~ 5 nm
    • Made of 13 longitudinal rows
    • of protofilaments
slide53

Microtubules

Made of abtubulin subunits

polymerize to form protofilaments (PF)

PF form sheets

Sheets form

microtubules

slide54

Microtubules

  • Protofilaments are polar
  • -tubulin @ - end
  • -tubulin @ + end
  • all in single MT have same polarity
slide55

Microtubules

In constant flux

polymerizing &depolymerizing

Add to  (+)

Fall off  (-)

slide56

Microtubules

Control growth by controlling

rates of assembly &disassembly

because these are distinct processes

can be controlled independently!

ColchicinemakesMTs disassemble

Taxol prevents disassembly

slide57

Microtubules

Control growth by controlling rates of assembly &disassembly

Are constantly rearranging inside plant cells!

slide58

Microtubules

  • Control growth by controlling rates of assembly &disassembly
  • Are constantly rearranging inside plant cells!
    • during mitosis & cytokinesis
slide59

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
slide60

µT Assembly

µTs always emerge from Microtubule-Organizing Centers (MTOC)

slide61

µT Assembly

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

slide62

Microtubules

  • MAPs (Microtubule Associated Proteins) may:
    • stabilize tubules
    • alter rates of
    • assembly/disassembly
    • crosslink adjacent
    • tubules
    • link cargo
slide63

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

slide64

µT functions

Give cells shape by guiding cellulose synth

slide65

µT functions

Give cells shape by guiding cellulose synth

Anchor organelles

slide66

µT functions

Give cells shape by guiding cellulose synth

Anchor organelles

Intracellular motility

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