Download Chapter Two Mineral Nutrition of Plant

Chapter Two
Mineral Nutrition of Plant
I Absorption of mineral elements by plant cells
1 Biological membrane
(1) Nature : selectivity permeability
(2) Composition:
①protein 30~40%
②phospholipid 40~50%
③carbohydrate , 10%~20%
④sterol
·Protein include extrinsic (peripheral protein ) intrinsic protein. (integral protein )and a anchored
protein. Their roles are tansport , structure.and transfer message etc.
·Phospholipid include polar head group composition: cholin, phosphate and glycerd. (nature:
water-loving or called hydrophilic ) and nonpoplar tail group (14~24 carbon atoms long-chain
fatty acids. Nature: water-fearing or called hydrophobic )
(3) Structure
·Phospholipids consist of a double layer (bilayer)
·Proteins associated with lipid bilayer are of three types: intrinsic (integral),extrinsic( peripheral),
and anchored. Integral proteins are embeded in the lipid bilayer, most integral proteins span the
entire width of the phospholipid bilayer. They serve as ion channels and certain receptors etc.
peripheral protein are bound to membrane surface by noncovalent bonds, such as ionic bonds or
hydrogen bonds. Peripheral proteins serve a variety of functions in the cell. Anchored protein are
bound to the menbrane surface via lipid molecules (fatty acid-anchored protein and glycosy
lphosphatidylinositol anchored protein and prenyl lipid-anchord protiens)
Fluid-mosaic model:
2. The types and mechanisms of solute absorption by plant cells.
(1) Types:
①Ion channel transport
②Ion pump transport
③Carrier transport
④Pinocytosis
(2)Mechanisms
① Ion channel transport major theory: There are ion channels (integral protein )in
plasmamembrane.
② Ion channel is activated by ion concentration gradient and membrane potential gradient
(Called electrochemical potential gradient )
③ Ion channel is opened
④ Ions into the cell following electrochemical potential gradient.
Kinds of ion channel

There are K+,,,,,Cl-,,,Ca2+ , NO3
For example
channels
K+ channel:
Composition
Two α-subunits
Voltage gate
Major part
Selectivity filter
Two β-subunits, Regulatory α-subunit
Transport speed: 107-108 ions·s-1
Distribution: 1 K+ channel·15 µm-2 in plasmamembrane.
250 k+ channel·4000 µm-2 Guard cell plasmamembrane
② Carrier transport
Uniport carrier
Kind of carrier
Symporter
Antiporter
S+C→S·C→S
into the cell
Following electrochemical
Potential gradient transport.
H+
+C→H+·A·C→H+·A
into the cell
A
H+ into the cell
H+(outside)
+C→H+·B·C
B(inside)
B out of the cell
Speed: 104-105 ions·s-1
3
③Ion pump transport
Kind
s
proton pump (H+-pump)
Calcium pump(Ca2+-pump)
Proton pump transport
Major theory
· A plasmamembrane H+-pump ATPase is effected by H+ cytosol.
· ATP hydrolysis.
·Uses the energy released to transport H+ (hydrogen ions) out of the cell.
·Establishes an electrochemical potential gradient
· Allows (Causes ) K+ and other positively charged ions to cross the membrane via a channel
protein.
·Negatively charged (I-)ions are transported along with H+ into the cell.
④Pinocytosis
· Substances (Ion or mocecule adsorb in the plasmamembrane.)
·Plasma membrane fold.
·Forma vescle
·Vescle into the cytosol or vacuole.
Figure 2.5
Summary:
Pinocytosis
Figure 2.6 Various solutes transport processes