Download Jan 22

Plan C
1.
2.
3.
4.
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 (microbodies)
1 membrane
Peroxisomes (microbodies)
found in (nearly) all eukaryotes
1 membrane
Fn:
1) destroy H2O2, other O2-related poisons
Peroxisomes
Fn:
1. destroy H2O2, other O2-related poisons
2. change fat to CH2O (glyoxysomes)
Peroxisomes
Fns:
1. destroy H2O2, other
O2-related poisons
2. change fat to CH2O
(glyoxysomes)
3. Detoxify & recycle
photorespiration products
Peroxisomes
Fn:
1.
2.
3.
4.
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
Bounded by 2 membranes
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
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
endosymbionts
1) Peroxisomes
2) Mitochondria
3) Plastids
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 b tubulin subunits
polymerize to form protofilaments (PF)
PF form sheets
Sheets form
microtubules
Microtubules
Protofilaments are polar
a-tubulin @ - end
b-tubulin @ + end
all in single MT have same
polarity
Microtubules
In constant flux
polymerizing & depolymerizing
Add to b (+)
Fall off a (-)
Microtubules
Control growth by controlling
rates of assembly & disassembly
because these are distinct processes
can be controlled independently!
Colchicine makes MTs 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 to minus end
“Walk” hand-over-hand towards chosen end
µT functions
1) Give cells shape by guiding cellulose synth
µT functions
1) Give cells shape by guiding cellulose synth
2) Anchor organelles
µT functions
1) Give cells shape by guiding cellulose synth
2) Anchor organelles
3) Intracellular motility