This document provides an overview of ion channels and membrane transport proteins. It lists 14 learning objectives related to understanding ion transport mechanisms, membrane potentials, the Nernst equation, Ohm's law, different types of ion channels, and patch clamp techniques. Key concepts covered include the distribution of ions inside and outside cells, equilibrium potentials, selectivity and permeation of potassium channels, and the role of PIP2 in channel gating.

1. • Ion Channels
Lecture 1 –Nernst Equation,
Ohm’s Law, Patch Clamp
Permeation and Gating

2. Learning Objectives
1. Know the classes of all membrane transport proteins and distinguish them according to
rates of transport.
2. Know the transporter reconstitution into liposomes method of studying the transport
process.
3. Describe Glucose transport through GLUT1 transporters as an example of a uniport-
catalyzed transport system. Know the mechanism thought to account for transport through
uniporters.
4. Understand how distribution of unbalanced charges at the membrane boundary accounts for
membrane potentials.
5. Know the distribution (low vs. high) of the four major ions in most mammalian cells.
6. Know the thermodynamic derivation of the Nernst Equation and be comfortable explaining it
qualitatively.
7. Given a membrane potential be able to determine the flow of ions (for a particular
distribution in and out of the cell) considering the relative magnitude and direction of the
chemical and electrical forces.
8. Be able to use Ohm’s law to determine the currents flowing through the cell membrane.
9. Given a membrane potential be able to determine the flow of ions (for a particular
distribution in and out of the cell) considering Ohm’s Law.
10. Know the different types of Ion Channels and the major features they possess.
11. Understand how the balance of currents determines the membrane potential.
12. Know the voltage clamp and all modes of the patch clamp techniques.
13. Predict how ion flux through a particular ion channel will influence the
membrane potential.
14. Understand how K ion selectivity, permeation and gating occurs.

6. From: Structure and function of facilitative sugar transporters.
Barrett et al, Current Opinion in Cell Biology 11, 496-502 (1999).

10. Distribution of Ions and the
Resting Potential
Na+
= 145 mM
Ca++
= 2 mM
K+
= 5 mM
Cl-
= 125 mM
Na+
= 15 mM
Ca++
= .0001 mM
K+
= 145 mM
Cl-
= 10 mM

11. Equlibrium potentials for major permeable ionic
species
In myocytes:
ENa = 61.5 log (145/15) = + 60 mV
ECa = 61.5 log (2/.0001) = + 131 mV
ECl = -61.5 log (125/ 10) = - 67 mV
EK = 61.5 log (5/ 145) = - 89 mV

21. Atomic Resolution Structures
Selectivity and Permeation

34. Atomic Resolution Structures
Gating

40. Inwardly rectifying K channels

41. Permeation pathways of Kir3.4 in a “closed” state and
Kv1.2 in an “open” state

42. From Nishida et al., 2007 EMBO J
26:4005-4015

43. PIP2 and the
cytoplasmic gates