1. Cells and cell growth Cell walls and membranes

2. Plant Cell Borders: Membranes and Wall Membranes – delimit the cell (plasma membrane) and organelles Compartmentalize functions – specialized organellar function Organellar sub compartments - separate reaction centers

3. Cell membranes: mostly lipids and proteins Lipids Glycerol backbone – conjugated to fatty acids Triacylglycerols – storage lipids, fatty acids at all positions, hydrophobic Glycerolipids – membrane lipids, polar group at the third position Phospho and galactolipids are amphipathic molecules – lipid bilayer structure

4. Fatty acids – long chain hydrocarbons (12 to 20 carbon residues) Saturated fatty acids – w/o double bonds Unsaturated fatty acids – w/double bonds

5. Membrane lipid bilayer arrangement Cellular membranes (glycerolipids) – ER and mitochondrial (phospholipids) plastids – (glactolipids)

6. Storage lipids in oil seeds Triacylgercerol - energy source during germination

7. Cutin, waxes and suberin – culticle (cutin and waxes) on stems and leaves, suberin in roots Culticle prevents water loss directly from epidermal cells Seals wounds – fruit cracking Defense Signaling molecules

8. Fatty acid synthesis in plastids First cycle - condensation of malonyl-ACP to acetyl-CoA = butyryl-ACP Subsequent cycles - condensation of malonyl-ACP to butyryl-ACP, etc. = chain elongation Taiz, Zeiger, 5 th ed.

9. Lipid biosynthesis in plastids and ER Plastids - fatty acid conjugation to glycerol-3-phosphate (G3P) to form phosphatidic acid → phospholipids and galactolipids ER – fatty acids transported from plastid → conjugation to G3P (phosphatidic acid → phospholipids and triacylglyerol lipids

10. Storage lipid conversion to sucrose Oil body – lipid hydrolyzed (lipases) to fatty acids Glyoxysomes - fatty acids oxidized to acetyl-CoA Acetyl-CoA - converted to succinate (glyoxylate cycle) Mitochondria - succinate transported to mitochondria and converted to malate Cytosol – malate transported to cytosol and converted to sucrose (gluconeogenesis)

11. Lipid functions Primary components of membranes Storage molecules for energy production Protective polymers Compartmentalization of reaction centers Regulate lipid and protein trafficking, and mineral ion and molecular uptake and efflux Signaling molecules

12. Cell Wall – polysaccharide framework of the cell border Most abundant carbon source in nature Mechanical rigidity of plants Controls cell volume and water status Determines cell shape Protects cells

13. Primary walls – extensible for elastic and plastic growth Secondary walls – internal to primary wall, not extensible Middle lamella joins adjacent cells Cell wall layers

14. Primary cell walls – cellulose microfibrils embedded in a hydrated matrix of non- cellulosic polysaccharides and structural proteins Arranged in microfibrils of several glucan chains (glucose polymers) Intramolecular hydrogen bonding

15. Hemicellulose, pectin and structural proteins in the primary cell wall Hemicellulose – glycan polymers that crosslink cellulose Pectin – galacturonic acid, hydrated gel phase of the wall Structural proteins - hydroxyproline/proline rich & glycoproteins cross-link the walls Wall loosening proteins – expansins & glucosylases/hydrolases Lignin – phenolic polymer, increases mechanical strength

16. Cellulose synthesis at the plasma membrane CESA rosette Cellulose microfibril 1,4  -glucan chain CESARosette subunitRosette CESA rosette (TEM)

18. Microtubules (cytoskeleton) direct orientation of cell wall – cellulose microfibrils microtubules cellulose synthase (CesA) overlay Science, 2006

19. CESA-YFPtubulin-YFPoverlay control destabilized Sciencemag.org

20. Microtubules (cytoskeleton) direct orientation of cell wall – cellulose microfibrils R.Weizbauer

21. Cell wall structure cellulose hemicellulose galacturones Cellulose synthase (Rosette) Golgi apparatus Cytoplasm secretory vesicles Plasma membrane

22. Cell expansion patterns – microtubule orientation directs microfibril distribution Localized growth or diffuse growth along an axis Random or directed growth

23. Smith et al. (2010) Cell expansion turgor pressure cell wall loosening water uptake

24. Secondary wall deposition – inwards from primary wall

25. Smith et al. (2010) Plant Biology Formation of woody tissue – perennials Secondary xylem (inside cambium) and secondary phloem (outside cambium)