Transcript 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