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The Na+-K+ ATPase Pump
Cardiac glycosides:
plant and animal steroids
Ouabain!
Digitalis!:
increased Na+ conc inside heart leads to stimulation of Na+Ca2+ exchanger, which extrudes sodium in exchange for
inward movement of calcium. Increased intracellular Calcium
stimulates muscle contraction.
The Na+-K+ ATPase Pump: Mechanism
Response of a human RBC to changes in osmolarity
of the extracellular fluid
The Na+-K+ ATPase Pump is required to maintain
Osmotic Balance and Stabilize Cell Volume
Sources of Intracellular Osmolarity:
large number of counterions (inorganic ions of opposite charge) that are attracted to large
macromolecules (most are charged).
small metabolites (high concentration of small organic molecules, sugars, amino acids, nucleotides)
and their counterions
Sources of Extracellular Osmolarity:
Due mainly to small inorganic ions - these leak slowly across the plasma membrane into the cell.
The problem:
Because of above factors, water moves into the cell by osmosis
The Solution:
Na+-K+ ATPase Pump
In vitro Investigation of The Na+-K+ ATPase Pump
Control of acid secretion in the stomach
Potassium channel
The Potassium Channel
Hinge-bending Model for the opening of
the Bacterial KcsA Channel.
The Structure of One subunit of a eukaryotic,
Voltage Gated K+ Channel
(Drosophila Shaker K+ Channel)
3-D Structure of a Voltage Gated Mammalian
K+ Channel
Conformational States of a Voltage Gated
K+ Ion Channel
A typical ion channel fluctuates between open
and closed states
The gating of ion channels
The technique of patch clamp recording
Measuring Ion Channel Conductance
Patch Clamp Recording
Patch Clamp Recording
The ionic basis of membrane potential
The membrane potential in animal cells
depends mainly on K+ Leak channels and
the K+ gradient across the plasma membrane
dGconc= -RT ln [Co]
[Ci]
dGvolt=zFV
dGconc + dGvolt = 0
Ion distribution is at equilibrium
across the membrane
The Nernst Equation and Ion Flow
V= RT ln Co
zF
Ci
The Resting Potential decays only slowly
when the Na+ K+ Pump is stopped