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Chapter 12: Transport Processes, pronounced sigh - Coggle Diagram
Chapter 12: Transport Processes
Diffusion, Osmosis, and Active Transport
Diffusion
random particle solution high to low
Osmosis
Diffusion through membrane
membrane types
differentially/selectively permeable membranes
only certain substances
ex: all lipid/protein membranes
completely impermeable
#
do not allow anything
Freely permeable
all solutes diffuse
little biological significance
Water molecules pass through all membranes
highly polar
more rapid with protein channels aquaporins
membranes
most have membrane bound molecular pumps
ATP used
if receiving side super conc.
active transport
intracellular transport
vesicles migrate through cytoplasm fuse w organelle
Active Transport
Water Potential
Cells and Water Movement
lysis
burst of cell
plant cells can never burst
counterbalance osm. pot.
plasmolysis
plasmolyzed
Cell loses water and shrinks
#
incipient plasmolysis
protoplast lose water pull from wall
shrinky cell
more solutes /unit water=osmotic pot. more negative
osm.pot. usually change only few megapascals
free energy
can be increased
being heated
elevated
put under pressure
can be decreased
cooling
reducing pressure
lowering it
Ψ=Ψπ + Ψp + Ψm
Ψp
Pressure Potential
effect pressure has on water pot.
pressure decrease-pressure pot and water pot decrease
can be positive (when something compressed)
or negative (something stretched)
Ψm
Matric Potential
water adhesion to nondissolved structures (cell walls, membrane, soil particles)
adhesion can only decrease waters free energy
always negative
Ψπ
Osmotic Potential
effect that solutes have on water pot.
adding solutes decrease water free energy
number of particles present in solution
always negative
potential is measured in megapascals (MPa) or bars
1 MPa approx.=10 bars (or atmospheres of pressure)
pure water at 1 atm. of pressure has water potential of 0
for living cells (Ψ=Ψπ + Ψp)
Short-Distance Intercellular Transport
Motor Cells
at "joints" flexure
ex: venus fly trap
similar to guard cells
accumulate or expel K+
adjust water pot/turgidity
pumping K+ out
Transfer Cells
active transport rate depend on molecular pumps present
#
smooth on outer surface
Guard Cells
at night, stomata closed
shrunken/little internal pressure
hydraulic equilibrium w surroundg cells
after sunrise, stomata open
K ions (K+) actively transported from sur to gu
cant leave guard cell membrane imperm
potassium pump is but diffusion not poss
stomatal pore
all living cells interconnected by plasmodesmata
symplast
all protoplasm, one continuous mass
apoplast
both wall and intercellular spaces
Long Distance Transport: Xylem
Water Transport Through Xylem
cohesion-tension hypothesis
stomatal pores open, allow water loss
apoplastic space- mesophyll, parenchyma filled w moist air
called transstomatal transpiration
water lost through cuticle
transcuticular transpiration
poikilohydry
body water content depending on habitat moisture
captivation
hydrogen bonding broken over large region
water columns break bc cohesion overcome
embolism
below captivation point
air bubble
Control of Water Transport by Guard Cells
water loss to atmosphere
turgid plant
light controls guard cell water relations
blue light important
close flavin or flavoprotien pigment
Properties of Water
water mol interact w many other substances
adhesive
adhere to soil particles
water interact strongly w water, behave weak
lq water cohesive
Water is heavy, lots of energy
Long-Distance Transport: Phloem
pressure flow hypothesis
membrane bound molecular pump, active transport
#
water and nutrients transport sites: sources
polymer trap mechanism
pronounced sigh
