Plant Cell Wall

primary cell wall

surround growing and dividing plant cells, provide mechanical strength but allow for expansion, outside

secondary cell wall

stronger and thicken than primary

endomembrane system components and function

nuclear envelope, endoplasmic reticulum, Golgi bodies + transport and secondary vesicles, plasma membrane and vacuolar membranes

function: modify package and transport lipids and proteins

rough endoplasmic reticulum description and function

flattened cisternae dotted with ribosomes, function is protein synthesis

smooth endoplasmic reticulum description and function

smooth flattened cisternae, function is lipid synthesis

Golgi apparatus description and function

stacks of cisternae in the order of forming, maturing, middle, and trans-Golgi network, function is synthesis and secretion of hemicellulose and pectin

cytoskeleton description and function

network of protein filaments that extend through the cytosol and contain microtubules, function is to 1) align cellulose microtubules as they are added to the cell wall 2) direct secretory Golgi vesicles toward developing wall 3) make up spindle fibres for chromosome movement and cell plate formation in dividing cells

the _____ _____ is responsible for cell size, shape, and texture of plant organ tissues, how do we know this

cell wall, treatment with wall degrading enzymes produces invariably round protoplasts

cell wall functions

mechanical properties contribute to complexity of plant cell size and shape, determine strength of plant structures, prevent ruptures of cell membrane, role in absorption transport and secretion of plant substances, defense against pathogens

3 polysaccharides in primary cell wall

pectin, hemicellulose, cellulose

cellulose synthesis location

plasma membrane

cellulose purpose

strengthen cell wall

how is cellulose synthesized

sucrose is fed into cellulose synthase and made into glucan chains, each cellulose synthase makes one glucan chain, glucan chains aggregate into microfibrils, microfibrils bundle into macrofibrils

matrix polysaccharides

pectin, hemicellulose

where are pectin and hemicellulose synthesized

Golgi apparatus, transported to plasma membrane in vesicles and released via exocytosis

hemicellulose function

help cohesion to form cellulose fibers, regulate cell enlargement

pectin function

prevent aggregation and collapse of cellulose network, resist compression

three components of secondary cell wall

lignin, hemicellulose, cellulose

the secondary cell wall has a (greater/smaller) proportion of cellulose than the primary cell wall, and (less/more) hemicellulose

greater, less

the three layers of the secondary cell wall differ by… and provide…

microfibril direction, laminated structure greatly increases strength

lignin synthesis location

secondary thickened cell wall tissues of lignin (biosynthesis of monolignols in cytosol)

lignin purpose

plant strength, facilitate upward water transport, barrier against pathogens

two bioeconomy uses of cell wall

1) polymeric materials from cell wall functionalized with chemical groups (cellulose nanocrystals, nanofibers, hemicelluloses)

2) biomass derived sugars and aromatics as substrate for hydrocarbon fuel conversation or monomers for polymerization into plastic