lecture 7 - cell wall Flashcards
What is the monomer of cellulose.
glucose
List the components of the plant primary cell wall and the phases they are apart of.
Crystalline Microfibrillar Phase: cellulose
Noncrystalline Matrix: pectin, hemicellulose, extensin (a protein)
Where is cellulose synthesised?
plasma membrane
Where are polysaccharides (pectin& hemicellulose) synthesised?
in the Golgi apparatus which are transported to the plasma membrane via vesicles
What are synthesised from rough ER?
extensin
What is the hemicellulose-rich layer that “sticks” the cell together called?
middle lamella
When does wilting occur?
when water is lost from plant cells, the protoplast no longer pushes against the cell wall
The secondary cell wall is produced only after what has stopped.
cell growth
What is the extensibility of cells is controlled by?
extensin cross linking
What process releases extracellular matrix proteins?
constitutive exocytosis
Describe the layout of the cell wall.
primary cell wall on the outer side
secondary cell wall is on the inner side
middle lamella is between the 2 adjacent plant cells
(like ECM)
What are 3 main functions in regulating cell shape.
influences cell morphology, provides structural support, prevents excessive water uptake
How do vacuoles have a role in regulating cell shape?
- high concentrations of solutes in vacuole
- water uptake into the vacuole by osmosis
- plant cell wall limits water uptake and prevents the cell bursting
- plant cells build up a large internal pressure that contributes to plant structural support
In what way can the orientation of the cellulose microfibrils influence cell morphology.
randomly orientation: expand equally
right angle to long axis of cell: expand longitudinally
What are the key differences in the secondary cell wall.
stronger, more cellulose, less pectin, lignin
