Agriculture Reference
In-Depth Information
Energy dissipated by movement of H + back
into cell coupled to transport of one molecule
of substrate in
Symporters
Zn 2 +
Fe 2 +
Mn 2 + H +
sucrose
H Na +
amino
acid
Antiporter
Energy dissipated by
movement of H + back into
cell coupled to active
transport of substrate out
H +
K +
H +
H +
H 2 PO 4
H +
H +
NO 3
Na +
CYTOSOL
Efflux
carrier
H +
NH 4 +
Antiporters
sucrose
Mg 2 +
H + pumps
Energy
from ATP
hydrolysis
used to
pump H +
out against
electro-
chemical
gradient
Cd 2 +
hexose
Ca 2 +
H +
ATP
H +
sucrose
H +
H +
ADP
+
P i
Na +
H +
H +
ABC
transporter
ATP
H +
H +
ATP
PC-Cd 2 +
ADP + P i
VACUOLE
ADP
+ P i
ATP
ADP
+
H +
ATP
P i
H +
anions,
cations
H +
pumps
H +
ADP
+ P i
ADP
+
2P i
PP i
P i
Ca 2 +
Ca 2 +
ATP
Tonoplast
Ca 2 +
pump
anions
(malate 2 ,
Cl , NO 3 )
Channels
Plasma
membrane
Inward
rectifying
Inward
rectifying
K +
Cl
Ca 2 +
K +
Outward
rectifying
Outward
rectifying
Channels
Transmembrane pores: selectivity for solutes
depends on biophysical properties that are
actively regulated
Figure 6.10 The main transport processes across the plasma membrane and tonoplast of
plant cells (adapted from Taiz and Zeiger, 2002). Reproduced by permission of Sinauer
Associates
The binding is highly selective and allows transport of a wide range of both
organic and inorganic solutes. The transport may be either passive, down an
electrochemical gradient, or, unlike for channels, active. If active, the carrier must
couple the energetically uphill transfer of solute to a separate energy-yielding
process. The coupling may be direct, for example to ATP hydrolysis as in H +
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