Download Bio 226: Cell and Molecular Biology

Pathogens
• Agrobacterium tumefaciens: Greg
• Agrobacterium rhizogenes
• Pseudomonas syringeae
• Pseudomonas aeruginosa: Mike
• Viroids: Bryant
• DNA viruses
• RNA viruses: Rob
• Fungi
• oomycetes
• Nematodes: Chris
Symbionts
• N-fixers
• Endomycorrhizae
• Ectomycorrhizae
Nutrient uptake
Most nutrients are dissolved in water
• Enter root through apoplast until hit endodermis
• Then must cross plasma membrane
Nutrient uptake
Then must cross plasma membrane
• Gases, small uncharged & non-polar molecules diffuse
down their ∆ [ ]
• Important for CO2, auxin & NH3 transport
Selective Transport
1) Channels
integral membrane proteins with pore that specific ions
diffuse through
Channels
driving force : electrochemical D
“non-saturable”
regulate by opening & closing
Channels
Stress-activated channels
open/close in response to
mechanical stimulation
voltage-gated channels
open/close in response to
changes in electrical potential
Channels
• Old model: S4 slides up/down
• Paddle model: S4 rotates
• 3 states
1.Closed
2.Open
3. Inactivated
Selective Transport
1) Channels
2) Facilitated Diffusion (carriers)
Carrier binds molecule
Selective Transport
Facilitated Diffusion (carriers)
Carrier binds molecule
carries it through membrane
& releases it inside
Selective Transport
Facilitated Diffusion (carriers)
Carrier binds molecule
carries it through membrane
& releases it inside
driving force = ∆ [ ]
Selective Transport
Facilitated Diffusion (carriers)
Carrier binds molecule
carries it through membrane
& releases it inside
driving force = ∆ [ ]
Important for sugar
transport
Active Transport
Integral membrane proteins
• use energy to transport specific ions against their ∆ [ ]
• allow cells to concentrate some chemicals, exclude others
Active Transport
Characteristics
1) saturable
2) specific
3) active: transport up ∆ [ ] (or ∆ Em)
4 classes of Active transport ATPase proteins
1) P-type ATPases (P = “phosphorylation”)
• Na/K pump
• Ca pump in ER & PM
• H+ pump in PM
• pumps H+ out of cell
4 classes of Active transport ATPase proteins
1) P-type ATPases (P = “phosphorylation”)
2) V-type ATPases (V = “vacuole”)
• H+ pump in vacuoles
4 classes of Active transport ATPase proteins
1) P-type ATPases (P = “phosphorylation”)
2) V-type ATPases (V=“vacuole”)
3) F-type ATPases (F = “factor”) a.k.a. ATP synthases
• mitochondrial ATP synthase
• chloroplast ATP synthase
4 classes of Active transport ATPase proteins
1) P-type ATPases (P = “phosphorylation”)
2) V-type ATPases (V = “vacuole”)
3) F-type ATPases (F = “factor”)
4) ABC ATPases (ABC = “ATP Binding Cassette”)
• multidrug resistance proteins
4 classes of Active transport ATPase proteins
1) P-type ATPases (P = “phosphorylation”)
2) V-type ATPases (V = “vacuole”)
3) F-type ATPases (F = “factor”)
4) ABC ATPases (ABC = “ATP Binding Cassette”)
• multidrug resistance proteins
pump hydrophobic drugs out of cells
very broad specificity
Secondary active transport
Uses ∆ [ ] created by active transport to pump something
else across a membrane against its ∆ [ ]
Secondary active transport
Uses ∆ [ ] created by active transport to pump something
else across a membrane against its ∆ [ ]
Symport: both substances pumped same way
Secondary active transport
Uses ∆ [ ] created by active transport to pump something
else across a membrane against its ∆ [ ]
Symport: both substances pumped same way
Antiport: substances
pumped opposite ways
Secondary active transport
Uses ∆ [ ] created by active transport to pump something
else across a membrane against its ∆ [ ]
Symport: both substances pumped same way
Antiport: substances
pumped opposite ways
Nutrient uptake
Gases enter/exit by diffusion down their ∆ [ ]
Nutrient uptake
Gases enter/exit by diffusion down their ∆ [ ]
Ions vary dramatically!
Nutrient uptake
Gases enter/exit by diffusion down their ∆ [ ]
Ions vary dramatically!
H+ is actively pumped out of cell by P-type H+ -ATPase
Nutrient uptake
Ions vary dramatically!
H+ is actively pumped out of cell by P-type H+ -ATPase
and into vacuole by V-type ATPase & PPase
Nutrient uptake
H+ is actively pumped out of cell by P-type H+ -ATPase
and into vacuole by V-type ATPase & PPase
• Main way plants make membrane potential (∆Em)!
Nutrient uptake
H+ is actively pumped out of cell by P-type H+ -ATPase
and into vacuole by V-type ATPase & PPase
• Main way plants make membrane potential (∆Em)!
• Used for many kinds of transport!
Nutrient uptake
Many ions are imported by multiple transporters with
varying affinities
Nutrient uptake
Many ions are imported by multiple transporters with
varying affinities
• K+ diffuses through channels down ∆Em: low affinity
Nutrient uptake
Many ions are imported by multiple transporters with
varying affinities
• K+ diffuses through channels down ∆Em: low affinity
• Also taken up by H+ symporters : high affinity
Nutrient uptake
Many ions are imported by multiple transporters with
varying affinities
• K+ diffuses through channels down ∆Em: low affinity
• Also taken up by H+ symporters : high affinity
• Low affinity is cheaper
but less effective
Nutrient uptake
K+ diffuses through channels down ∆Em: low affinity
Also taken up by H+ symporters : high affinity
Low affinity is cheaper but less effective
some channels also transport Na+
Nutrient uptake
K+ diffuses through channels down ∆Em: low affinity
Also taken up by H+ symporters : high affinity
Low affinity is cheaper but less effective
some channels also transport Na+
why Na+ slows K+ uptake?
Nutrient uptake
K+ diffuses through channels down ∆Em: low affinity
Also taken up by H+ symporters : high affinity
Low affinity is cheaper but less effective
some channels also transport Na+
why Na+ slows K+ uptake?
Na+ is also expelled
by H+ antiport
Nutrient uptake
Na+ is also expelled
by H+ antiport
•Enters through channels
Ca2+ is expelled by P-type
ATPases in PM
Nutrient uptake
Ca2+ is expelled by P-type ATPases in PM
& pumped into vacuole & ER by H+ antiport & P-type
Nutrient uptake
Ca2+ is expelled by P-type ATPases in PM
pumped into vacuole & ER by H+ antiport & P-type
• enters cytosol via gated channels
Nutrient uptake
PO43-, SO42-, Cl- & NO3enter by H+ symport
Nutrient uptake
PO4, SO4, Cl & NO3 enter by H+ symport
• also have anion channels of ABC type
Nutrient uptake
PO43-, SO42-, Cl- & NO3- enter by H+ symport
• also have anion transporters of ABC type
• and anion channels
Nutrient uptake
PO43-, SO42-, Cl- & NO3- enter by H+ symport
• also have anion transporters of ABC type
• and anion channels
Plants take up N many ways
Nutrient uptake
Plants take up N many ways: NO3- & NH4+ are main
forms
Nutrient uptake
Plants take up N many other ways
• NO3- also by channels
• NH3 by diffusion
• NH4+ by carriers
Nutrient uptake
Plants take up N many other ways
• NO3- by channels
• NH3 by diffusion
• NH4+ by carriers
• NH4+ by channels
Nutrient uptake
Plants take up N many other ways
• 3 families of H+ symporters take up amino acids
Nutrient uptake
Plants take up N many other ways
•3 families of H+ symporters take up amino acids
•Also have many peptide transporters
• some take up di- & tripeptides by H+ symport
Nutrient uptake
Plants take up N many other ways
•3 families of H+ symporters take up amino acids
•Also have many peptide transporters
• some take up di- & tripeptides by H+ symport
• others take up tetra- &
penta-peptides by H+ symport
Nutrient uptake
Plants take up N many other ways
•3 families of H+ symporters take up amino acids
•Also have many peptide transporters
• some take up di- & tripeptides by H+ symport
• others take up tetra- &
penta-peptides by H+ symport
Also have ABC transporters
that import peptides
Nutrient uptake
Plants take up N many other ways
•3 families of H+ symporters take up amino acids
•Also have many peptide transporters
• some take up di- & tripeptides by H+ symport
• others take up tetra- &
penta-peptides by H+ symport
Also have ABC transporters
that import peptides
N is vital!
NO3- & NH4+ are main forms
Nutrient uptake
Metals are taken up by ZIP proteins & by ABC
transporters
• same protein may import Fe, Zn & Mn!
Nutrient uptake
Much is coupled to
pH gradient
Nutrient transport in roots
Move from soil to endodermis in apoplast
Nutrient transport in roots
Move from soil to endodermis in apoplast
Move from endodermis to xylem in symplast
Nutrient transport in roots
Move from endodermis to xylem in symplast
Transported into xylem by H+ antiporters
Nutrient transport in roots
Move from endodermis to xylem in symplast
Transported into xylem by H+ antiporters, channels
Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps
Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps
Lowers xylem water
potential -> root pressure
Water Transport
Passes water & nutrients to xylem
Ys of xylem makes root pressure
Causes guttation: pumping water into shoot
Transport to shoot
Nutrients move up
plant in xylem sap
Nutrient transport in leaves
Xylem sap moves through apoplast
Leaf cells take up what
they want