Chapter 3 Flashcards
Most plant transporter genes are members of _______________ ____________ that show developmental and tissue-specific expression.
multigene families
Central functions of membrane transporters in response to physiological stimuli including abiotic and biotic __________ and how the activities of individual transporters are coordinated within a network at the cell and tissue levels.
stresses
MEMBRANES FACILITATE ______________________!!!!!
COMPARTMENTALIZATION!!!!
___________ displays anomalously high permeability in biological membranes.
Water
Compartmentalization of ______________ within membrane-bound organelles not only concentrates reactants and catalysts, but also segregates incompatible processes. This division of labor facilitates metabolic ______________ and _________________.
solutes; flexibility and efficiency
Membrane transport underlies many essential cell biological processes. Name 7 of them.
- Nutrient acquisition.
- Metabolite distribution.
- Compartmentalization of metabolites.
- Energy transduction.
- Turgor generation.
- Waste product excretion.
- Signal transduction.
Transport proteins can be regarded as ______________ enzymes.
conventional
Pumps catalyze ______ transport, coupling the energy liberated from ________________ of _____ to transport of a specific molecule against an electrochemical gradient.
active; hydrolysis; ATP
Channels and cotransporters facilitate _______ transport, utilizing energy stored in ______________________ _____________ to power transport.
passive; electrochemical gradients
______________: form aqueous pores in the membrane to allow for passive transport.
channels
___________________: transport specific molecules against an electrochemical gradient for passive transport.
cotransporters (carriers)
In passive transport, the net change in free energy for all molecules transported is _______________.
negative
Identify pumps, channels and cotransporters
!!
What is the name for cotransporters that catalyze solute flux in the same direction as H+ or Na+ flux?
symporters
___ ________ and ___ ______________ are the key players in determining the membrane potential of a cell.
H+ pumps; K+ channels
A membrane potential or voltage results from gradients of _________ and _________ across the membrane.
cations and anions
Living cells generally have a _______________ membrane potential.
negative
Living cells generally have a negative membrane potential, because electrical potential favors release of __________ charged solutes and uptake of ___________ charged solutes.
negatively; positively
__________ ____________ at the inner mitochondrial and thylakoid membranes are H+-pumps that synthesize ATP.
F-type ATPases
(f=factory so synthesize ATP)
____________ _____________ covalently bind the γ-phosphate of ATP during catalysis.
P-type ATPases
F-type ATPases harness pmf to drive ATP ___________.
F= factory
synthesis
P-type PM H+-ATPase generates pmf by ___________ ATP.
hydrolyzes
Most enzymes, PM H+-ATPase, that play pivotal roles in metabolism are subject to intense regulation. The pump is activated in response to lowered _______________ ___.
cytosolic pH
DEFINITION: a toxin produced by a fungal pathogenic plant, Fusicoccum amygdali, that stimulates the P-type H+ ATPase.
fusicoccin
PM H+-ATPase is activated by the ____________ and binding of 14-3-3 proteins.
phosphorylation
________-_________ pumps are major players in the sequestration of AMPHIPATHIC METABOLITES and xenobiotics into the vacuole.
ABC-type pumps
________: K+ influx channel; K+ uptake in roots
AKT1
Arabidopsis akt1 mutants that are deficient in the AKT1 inward rectifying channel demonstrate ________________ growth in comparison to the wild type.
diminished
DEFINITION: a superfamily of voltage-gated K+, Ca2+, and Na+ channels found in animal cells and named for the Drosophila mutant from which the first outward rectifying K+ channel was cloned.
Shaker family
DEFINITION: a transmembrane protein that is involved in the opening of a channel in response to a permissive voltage.
voltage sensor
The activity of voltage-dependent K+ channels at the plasma membrane is regulated by _______________ and _____________________.
voltage and phosphorylation
Monovalent _____________ ____________ at the vacuolar membrane are [Ca2+]-sensitive and mediate vacuolar K+ mobilization.
cation channels
Activities of vacuolar FV K+ channels depend on _______________ ____ and ____.
whether the channel is open or closed
cytosolic pH and Ca2+.
High-affinity ___ ______________ are present at the plasma membrane.
K+ transporters
Besides the biophysically and physiologically well-studied functions of K+ channels, plants possess a large number of K + transporters that do NOT belong to typical ____ __________ families.
transporters are different from channels
ion channel
Ca2+ ions are taken up into the cytosol predominantly by ion channels, rather than __________-_____________ transporters.
proton-coupled
