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Plan C 1.Pick a problem 2.Pick some plants to study 3.Design some experiments 4.See where they lead us.

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Presentation on theme: "Plan C 1.Pick a problem 2.Pick some plants to study 3.Design some experiments 4.See where they lead us."— Presentation transcript:

1 Plan C 1.Pick a problem 2.Pick some plants to study 3.Design some experiments 4.See where they lead us

2 Endomembrane system Organelles derived from the ER 1) ER 2) Golgi 3) Vacuoles 4) Plasma Membrane 5) Nuclear Envelope 6) Endosomes 7) Oleosomes

3 VACUOLES Vacuoles are subdivided: lytic vacuoles are distinct from storage vacuoles!

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

5 endosymbionts derived by division of preexisting organelles no vesicle transport Proteins & lipids are not glycosylated

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

7 Peroxisomes (microbodies) 1 membrane

8 Peroxisomes (microbodies) found in (nearly) all eukaryotes 1 membrane Fn: 1) destroy H 2 O 2, other O 2 -related poisons

9 Peroxisomes Fn: 1.destroy H 2 O 2, other O 2 -related poisons 2.change fat to CH 2 O (glyoxysomes)

10 Peroxisomes Fns: 1.destroy H 2 O 2, other O 2 -related poisons 2.change fat to CH 2 O (glyoxysomes) 3.Detoxify & recycle photorespiration products

11 Peroxisomes Fn: 1.destroy H 2 O 2, other O 2 -related poisons 2.change fat to CH 2 O (glyoxysomes) 3.Detoxify & recycle photorespiration products 4.Destroy EtOH (made in anaerobic roots)

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

13 endosymbionts 1) Peroxisomes (microbodies) 2) Mitochondria

14 Mitochondria Bounded by 2 membranes

15 Mitochondria 2 membranes Smooth OM

16 Mitochondria 2 membranes Smooth OM IM folds into cristae

17 Mitochondria -> 4 compartments 1) OM 2) intermembrane space 3) IM 4) matrix

18 Mitochondria matrix contains DNA, RNA and ribosomes

19 Mitochondria matrix contains DNA, RNA and ribosomes Genomes vary from 100,000 to 2,500,000 bp, but only genes

20 Mitochondria matrix contains DNA, RNA and ribosomes Genomes vary from 100,000 to 2,500,000 bp, but only genes Reproduce by fission

21 Mitochondria matrix contains DNA, RNA and ribosomes Genomes vary from 100,000 to 2,500,000 bp, but only genes Reproduce by fission IM is 25% cardiolipin, a bacterial phospholipid

22 Mitochondria Genomes vary from 100,000 to 2,500,000 bp, but only genes Reproduce by fission IM is 25% cardiolipin, a bacterial phospholipid Genes most related to Rhodobacteria

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

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

25 endosymbionts 1)Peroxisomes 2)Mitochondria 3) Plastids

26 Plastids Chloroplasts do photosynthesis Amyloplasts store starch Chromoplasts store pigments Leucoplasts are found in roots

27 Chloroplasts Bounded by 2 membranes 1) outer envelope 2) inner envelope

28 Chloroplasts Interior = stroma Contains thylakoids membranes where light rxns of photosynthesis occur mainly galactolipids

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

30 Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes

31 Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes Closest relatives = cyanobacteria

32 Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes Closest relatives = cyanobacteria Divide by fission

33 Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes Closest relatives = cyanobacteria Divide by fission Fns: Photosynthesis

34 Chloroplasts Fns: Photosynthesis & starch synth Photoassimilation of N & S

35 Chloroplasts Fns: Photosynthesis & starch synth Photoassimilation of N & S Fatty acid & some lipid synth

36 Chloroplasts Fns: Photosynthesis & starch synth Photoassimilation of N & S Fatty acid & some lipid synth Synth of ABA, GA, many other biochem

37 Chloroplasts & Mitochondria Contain eubacterial DNA, RNA, ribosomes Inner membranes have bacterial lipids Divide by fission Provide best support for endosymbiosis

38 Endosymbiosis theory (Margulis) Archaebacteria ate eubacteria & converted them to symbionts

39 Endosymbiosis theory (Margulis) Archaebacteria ate eubacteria & converted them to symbionts

40 Endosymbiosis theory (Margulis) Archaebacteria ate eubacteria & converted them to symbionts

41 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

42 Cytoskeleton Actin fibers (microfilaments) ~7 nm diameter Form 2 chains of polar actin subunits arranged in a double helix

43 Actin fibers polar subunits arranged in a double helix Add to + end Fall off - end Fn = movement

44 Actin fibers Very conserved in evolution Fn = motility Often with myosin

45 Actin fibers Very conserved in evolution Fn = motility Often with myosin: responsible for cytoplasmic streaming

46 Actin fibers Very conserved in evolution Fn = motility Often with myosin: responsible for cytoplasmic streaming, Pollen tube growth & movement through plasmodesmata

47 Actin fibers Often with myosin: responsible for cytoplasmic streaming, Pollen tube growth & movement through plasmodesmata

48 Intermediate filaments Protein fibers 8-12 nm dia (between MFs & MTs) form similar looking filaments Conserved central, rod-shaped  -helical domain

49 Intermediate filaments 2 monomers form dimers with parallel subunits Dimers form tetramers aligned in opposite orientations & staggered

50 Intermediate filaments 2 monomers form dimers with parallel subunits Dimers form tetramers Tetramers form IF

51 Intermediate filaments 2 monomers form dimers with parallel subunits Dimers form tetramers Tetramers form IF Plants have several: Fn unclear

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

53 Microtubules Made of  tubulin subunits polymerize to form protofilaments (PF) PF form sheets Sheets form microtubules

54 Microtubules Protofilaments are polar  - end  + end all in single MT have same polarity

55 Microtubules In constant flux polymerizing & depolymerizing Add to  (+) Fall off  (-)

56 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

57 Microtubules Control growth by controlling rates of assembly & disassembly Are constantly rearranging inside plant cells!

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

59 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

60 µT Assembly µTs always emerge from Microtubule-Organizing Centers (MTOC)

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

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

63 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

64 µT functions 1)Give cells shape by guiding cellulose synth

65 µT functions 1)Give cells shape by guiding cellulose synth 2)Anchor organelles

66 µT functions 1)Give cells shape by guiding cellulose synth 2)Anchor organelles 3)Intracellular motility


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