Plant Bio 2 Flashcards
What is the c ell wall made of
Cellulose
How much dry weight of a plant does the cell wall take up
15-30% is the cell wall
What is a primary cell wall
What is a secondary cell wall
A extracellular wall made outside the plasma membrane of a plant cell, all cells have
Made after the primary, only some cells have
What cells have secondary cell walls
Rigid cells like xylem
Lignin (give strength to secondary cell wall)
What is the middle lamella
It’s between cells wall and glued cells together
Ex. Pectin (a polysaccharide)
What is the order of cell wall layers
Middle lamella
Primary
Secondary
Plasma membrane
What is hydrostatic pressure
Pressure in plant cells due to water and turgor pressure
Plant cells have high hydrostatic pressure
What does the primary cell wall help with in terms of hydrostatic pressure
Is stops the wall from bursting
The inside of a cell has ____ solute concentration
High
Solutes: ions, sugar
How does osmosis cause high turgor pressure
Water goes in cell since high solute pressure
Then cause turgor pressure in the cell
How does turgor pressure help
It’s important in keeping the leaf shape
If water level decreases, the plant wilts
What is the cell wall made of
Polysaccharide and protiens
- Cellulose microfibrils
- Hemicellulose
- Pectins
- Protiens
What are Cellulose microfibrils
1000s of Polymers of glucosyl subunits (beta 1,4 linkages of glucose) bundled together
Give strength and structure
What is Hemicellulose
Give example
Through hydrogens bonds, it cross links cellulose microfibrils together
It’s a linear polymer of glucose and another sugar
For example. Xyloglucan. A hemicellulose made of glucose and xylose (sugar)
What are pectins
They determine the porosity of the cell wall
If more pectins, less porous wall
They also bind protiens
What are protien roles in the cell wall
Wall stability and loosening
What is the expansin protien
It breaks the hydrogen bonds between cellulose and hemicellulose
To loosen the cell wall
How are cellulose microfibrils made
Made by cellulose synthase in the plasma membrane
So cellulose synthase in The form of a 6 membered rosette takes glucose from the cytoplasm and turns it into cellulose microfibrils
The microtubules guide the direction of the cellulose synthase movement
How are hemicellulose and pectin made
They’re made in the golgi stacks
How are protiens of the cell wall made
Made in the rough ER, move through the golgi, and are deposited into vesicles at the trans golgi network
Then the vesicles fuse with the plasma membrane and are deposited in the cell wall
How do cellulose microfibrils help in growth of a cell that’s elongating
Ex. In root cells
The microfibrils are In the shape of hoops and so are the microtubules
This slinky shape lets it grow vertically but not laterally so over time the cell would grow upward
What things cause cell elongation
Turgor pressure
Cell wall loosening
Orientation of the cellulose microfibrils (curve shape)
In what manner does plant elongate their cells
In a circular manner where it finds something to grab onto and elongate
