(5) Transport in Plants

• when something moves in or out(down its concentation gradient)
• moves high to low

uses transport proteins

has a receptor site and changes conformation

for ions, gated

uses ATP directly, in plants involves proton pump (found in plasma membrane of cells)

generated by pumping protons out

negative outside and positive inside

substances want to diffuse down their chemical gradient (cells want to come back in)

a source of potential energy that allows cells to do work, caused by the electrochemical gradient

uses ATP indirectly, needs cotransport proteins

couple the downhill movement with the uphill movement of something else

creation of a transmembrane proton graient which genrats a membrane potential which is a source of potential energy that the cell can use to do work

diffusion of water across a semi permeable membrane

channel proteins specific to water

hypotonic to hypertonic

created when water comes into a plant cell and the plasma membrane presses on the cell wall

turgor pressure

the pressure of water coming in

form of potential energy

megapascals

lower

any pressure less than 1 atm (TENSION)

sucking a straw lowers water potential

any pressure greater that 1atm

injecting a syringe raises water potential

• transmembrane
• symplastic
• apoplastic

• slowest, most complex, very unlikely and selective
• crosses the plasma membrane over and over
• needs carrier/transport proteins

• crosses the plasma membrane once
• selective
• fast because of plasmodesmata

• never crosses a membrane
• oozes along pores of the cell wall
• fast and nonselective

• region of wax on epidermis that blocks the apoplastic route, therfore forcing the symplastic route, which forces selectivity
• (lateral transport in roots)

evaporation of water from leaves of a plant

• pushing
• pulling

weak force caused by root pressure where solutes are actively transported from soil into xylem

water potential of stele is less that cortex and soil, so the water moves in and raises water potential, which pushes xylem sap up, then guttation occurs

xylem sap fills up the spongy mesophyll and it comes out the stoma, ex. of root pressure

• transpiration cohesion tension mechanism
• solar powered so no ATP needed

• 1. transpiration occurs, providing energy to pull xylem sap and cool down leaves
• 2. cohesion happens
• 3. transpiration creates tension, which causes water to move from regions of high water potential to those with low water potential
• 4. evaporating water increases the meniscus which stretches H bonds

water molecules stick together because of H bonds

a negative pressure that lowers water potential

curved region where air and water interface, forms at junction of cells and air space of spongy mesophyll