lecture 14

Question 1

describe the cell wall

Answer 1

primary wall (thin)
3 layers of secondary wall (larger support)
middle lamella (pectin sticky carbs)

Question 2

cellulose 4 facts

Answer 2

most abundant organic macromolecule on earth
a glucose monomer
highly ordered
long, ribbon like structures

Question 3

cell wall composition

Answer 3

crystalline microfibrillar phase
- cellulose (25-30%)
non-crystalline matrix
- pectic polysaccharides (35%)
- hemicellulosic polysaccharides (15-25%)
protein
-extensin (5-10%)

Question 4

primary cell wall protein

Answer 4

extensin cross linking of pectin and cellulose dehydrates the cell wall,
reduces extensibility and increases strength

Question 5

synthesis of cell wall

Answer 5

1. cellulose microfibrils at plasma membrane (multisubunit complex of enzyme cellulose synthesis)
2. polysaccharides (pectin and hemicellulose) from golgi
3. cell wall proteins (extensins) from rough ER

Question 6

cell wall function

Answer 6

1. structural support and cell morphology
2. protection
3. prevents excessive water uptake

Question 7

orientation of cellulose microfibrils influences what

Answer 7

cell morphology (expand equally, longitudinally)

Question 8

plant vacuole osmotic pressure

Answer 8

negative osmotic pressure water enters=turgor pressure

Question 9

microfibrils organisation in 3 layers secondary wall

Answer 9

random orientations=strength

Question 10

Secondary cell wall

Answer 10

more cellulose
less pectin
15-35% lignin

Question 11

lignin

Answer 11

second most abundant organic macromolecule
complex phenolic polymer
confers strength, rigidity, hydrophobicity

Question 12

virus movement plasmodesmata

Answer 12

gating proteins

viral nuclic acids pulled through