Transcript Ca channel

Ion Channels in the
Plasma Membrane of
Pollen Tube
Presented by Xia Fan
Introduction
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What Are Ion Channels:
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They are pore-forming proteins that help establish the small
voltage gradient that exists across the membrane of all living
cells, by controlling the flow of ions.
Archetypal channel pore is just one or two atoms wide at its
narrowest point. It conducts a specific species of ion and
conveys them through the membrane single file--nearly as fast as
the ions move through free fluid. In some ion channels, access to
the pore is governed by a "gate," which may be opened or closed
by chemical or electrical signals, or mechanical force, depending
on the variety of channel.
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Different Types of Ion Channels:
Voltage-gated channels open or close, depending on the transmembrane
potential.
Stretch-activated channels open their pores in response to mechanical
deformation of the plasma membrane. Though little is known about these
channels, they may be linked to molecules in the cytoskeleton, which may
open them by transmitting physical forces of stretch or pressure to the
channels, causing them to undergo a conformational change. The channels
may also be pulled open due to tension on the membrane itself . Opening the
channels allows ions to which they are permeable to flow down their
electrochemical gradients into or out of the cell, causing a change in
membrane potential.
Identification and Characterization
of SA Ion Channels in Pollen
Protoplasts
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Result
SA Ca2+ channels are identified in pollen grain and tube tip
protoplasts, with similar but not identical properties. These
channels were localized to a small region of the grain protoplasts
associated with the site of tube germination.
SA K+ and spontaneous K+ channel are identified in pollen
grain and they are distributed over the entire grain surface, but
neither was present at the germination site or at the tip.
Neither SA channel was detected in the grain protoplasts unless
the grains were left in germination medium for at least 1 h.
Spontaneous K+ Channels in Grain
Protoplasts