Cell wall and roles in regulating plant cell shape - 7

Question 1

What is the major component of the primary cell wall

Answer 1

Cellulose (most abundant organic molecule on earth)

Question 2

What phase is cellulose in and what form (in primary cell wall)

Answer 2

Phase 1 - Cellulose creates crystalline microfibril ribbons with highly ordered structures bonded together.

Question 3

What components make up Phase 2 (primary cell wall)

Answer 3

Non-crystalline matrix.
Hemicellulose forms a long chain of single sugar. This forms a rigid structure.
Pectin branch of negatively charged polysaccharides that bind water and have gel-like properties.

Question 4

What purpose does Phase two have (primary cell wall)

Answer 4

Extensin protein cross links pectin and cellulose, this dehydrates the cell wall reducing extensibility and increasing the strength. Also controls the expansion of the cell.

Question 5

How is the primary cell wall synthesised

Answer 5

Rosettes move parallel to the cortical microtubes, laid at membrane. Polysaccharides from Golgi move to cell wall. Proteins build up wall (constitutive exocytosis)

Question 6

What synthesises cellulose

Answer 6

Rosettes

Question 7

What is the structure and purpose of the vacuole

Answer 7

Surrounded by a highly selective membrane that allows water to pass passively. It can build up a large internal pressure and prevents cell from bursting.

Question 8

What is isotonic

Answer 8

When water goes in and out of vacuole (flacid)

Question 9

What happens when there is too much water in a cell

Answer 9

It becomes hypotonic (turgid)

Question 10

What happens when a cell has too little water

Answer 10

It becomes hypertonic (shrivelled) (plasmolysis)

Question 11

What is the different between the primary and secondary cell wall

Answer 11

Secondary is thicker and stronger. It has more cellulose and lignin and less pectin

Question 12

What is the structure of the secondary cell wall

Answer 12

Has multiple layers of cellulose with different orientations. Lignin creates a complex polymer that creates hollow tubes to exclude water.

Question 13

What is the purpose of the secondary cell wall

Answer 13

structural integrity ad water transport in and out of cell.

Question 14

What is the function of the plasmodesmata

Answer 14

It is an intercellular connection that allows cell-cell communication and movement of small molecules. Connects the ERs.