Turgor pressure Flashcards
Whats the key difference between animal and plant cells?
Plant cells have a cell wall and a vacuole (to generate huge pressures)
How is pressure generated in cell walls?
The cell wall restricts the expansion of the protoplast
What is on example of a turgor driven movement?
Venus fly trap
How is turgor pressure used in movement processes of plants? (5)
- gravitropism
- hydrotropism
- light stimulated responses
- reproduction
- pollen tube growth
Why is turgor pressure so vital in the support of plants? (4)
- loss of turgor in non woody tissues causes wilting which limits photosynthesis
- can’t transport any sugars as the phloem doesn’t have any pressure
- leaves can’t intersect light as they have drooped
- damage to cells lead to non-functioning
What role does turgor pressure play in the stomata?
- 2 guard cells shut when turgor pressure drops
How is turgor pressure generated?
- water moves into cell by osmosis
- because solutes accumulate in the vacuole
- vacuole swells and the protoplast is pushed against cell wall
Define turgor pressure
the force within the cell that pushes the plasma membrane against the cell wall.
Define osmosis
diffusion of water down its own concentration gradient
What is the effect of solutes on the cell wall?
solutes added decrease teh concentration of water, pure water outside cell wall will diffuse in
What is the most pressured compartment in a plant cell?
The phloem
Why is the structure of the membrane important in cells?
Its semi permeable to allow water to cross the wall by osmosis
What is the difference between hypertonic and hypotonic solutions?
Hypertonic solutions have a higher concentration of solutes whereas hypotonic have a lower concentration
What the effects of a hypotonic solution on turgor pressure in cells?
Cells gain water and protoplast is pushed against cell wall
What the effects of a hypertonic solution on turgor pressure in cells?
a cell wall gives no advantages, cell looses water, volume shrinks, membrane pulls away from cell wall
What are aquaporins?
membrane proteins forming water channels and are essentially the biochemical basis of osmosis
What is the role of aquaporins?
they can open and close to regulate the membrane permeability by closing them
What processes are balanced when the water pressure is 0?
- accumulation of solutes and lowering the concentration of water inside the cell
What does the water potential need to be in order for a cell to take up water and generate turgor pressure?
lower water potential than its environment
How do you make water potential more negative?
Lower the turgor pressure or increase teh osmotic pressure
What is the difference between the primary and the secondary cell wall?
primary= growing secondary= lignified remains of primary cell wall
How do plants grow?
by individual cells expanding by taking up more water
must have lower water potential on outside
What is the effect of turgor pressure on growth?
lower turgor = slower growth
higher turgor = faster growth
What is the plant’s cell wall made of?
cellulose microfibrils
What is the effect of temperature on cell walls?
lower temperature, less extensible cell walls
What is the difference between expansin and extension in the cell wall?
extensin = reduces extension expansin = allows extension
Name some cell wall components
cellulose hemicellulose pectin protein lignin
What is the effect of acid protons on the cell wall?
it will compete with the hydrogen bonding and will weaken teh hydrogen bonding, manipulating the ph of cell wall
What is teh acid growth hypothesis?
acidified walls will grow faster and loosens wall
Why does auxin stimulates growth?
- it stimulates the proton ATPase in the plasmalemma
- and it exudes protons into the cell wall
- and solidifies the cell wall by extension growth
- so increased cell extension by weakening hydrogen bonds between teh xylogucan and teh cellulose microfibrils
How is growth related to cell walls?
increase in growth is due to increased loosening of cell wall
What is the role of expansins?
loosen hydrogen bonds between xylogucan and cellulose
How does the tightening of cell walls lead to an increase in extension? (5)
- longitudinal microfibril orientation
- increase cross links between polymers
- de esterifying teh pectic acids
- increases pectin cacium bridges
- increase in extension
What is the secondary cell wall composed of and its role?
- cellulose and lignin
- mainly for support
What is the difference in extensibility between secondary and primary cell wall?
primary are extensible whereas secondary are not
What is the difference in lignin content between secondary and primary cell wall?
primary don’t have lignin whereas secondary do contain lignin
How do you calculate water potential?
Turgor pressure - osmotic pressure
Name 5 things that turgor pressure ahs a role in plants?
- stomata
- movement
- phloem
- growth
- suppoty
