Chloride Channel / Ion Channels / Integral Membrane Proteins .pdf

This pdf is about the Chloride Channel / Ion Channels / Integral Membrane Proteins.

For more details visit on YouTube; @SELF-EXPLANATORY; https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos

Thanks...!

1. selfexplanatory.2022
HelloHI
नमस्ते
ْم
ُ
كْيالاع ُمالََّسلا
َِّللَّٱ ُةامْحاراو
ُهُتاكاراباو
Saba Parvin Haque
M.Sc. Life Sciences
(Specialization in Neurobiology)
from “Sophia College”
(Autonomous), Mumbai.

2. Chloride
Channels

3. Ion channels are integral membrane proteins that form ion-
selective, water-filled pores across cellular membranes.
 Chloride channels are a subset of ion channels that are
selectively permeable to chloride and often to other small
monovalent anions.
Chloride channels are found in the plasma membranes of most
cells and in the membranes of various intracellular organelles
including the endoplasmic reticulum, Golgi apparatus,
endosomes and sarcoplasmic reticulum.
The physiological functions of chloride channels include
stabilization of resting membrane potentials in muscle and
nerve cells, transepithelial transport, cell volume regulation,
signal transduction and acidification of intracellular organelles.
Introduction

4. Figure

5. Figure

6. Three structural families of chloride channels have
been identified to date. These include the ClC
channel family, the cystic fibrosis transmembrane
conductance regulator (CFTR) and the g-
aminobutyric acid (GABA)-gated and glycine-
gated neurotransmitter receptors.
Functional data suggest that additional structural
classes of chloride channels exist, but the genes
encoding these channels have not yet been identified.
Genetic defects in chloride channels and abnormal
regulation of gating cause a variety of human
diseases.
Introduction

7. What
Chloride
Channels
Do for a
Cell ?
The effect of opening a chloride channel depends on
the driving force for chloride movement across the
cell membrane.
 The driving force is determined by the algebraic
sum of the transmembrane concentration gradient
for chloride and the transmembrane electrical
potential.
 The driving force is called the chloride electro-
chemical potential.
 When a chloride channel opens, chloride ions may
either enter or leave the cell depending on the
direction of the chloride electrochemical gradient.

8. What
Chloride
Channels
Do for a
Cell ?
For plasma membrane chloride channels the concentration
gradient is determined by the difference in the chloride
concentration in the extracellular and intracellular fluid.
Chloride is the major negatively charged ion in the
extracellular fluid.
In mammals the extracellular fluid chloride concentration is
about 100 mmol L
-1
 The concentration of chloride inside cells is variable and
depends on the types of chloride transport proteins present in
the plasma membrane. If ion-coupled chloride transporters,
such as the Na
+
/Cl
-
or Na
+
/K
+
/2CK
-
cotransporters, are
present in the plasma membrane, the intracellular chloride
concentration tends to be high( ~20 mmol L
-1
)

9. Figure

10. In cells lacking these transporters, the chloride concentration is lower, about 5
mmol L
-1
The resting transmembrane electrical potential is always negative inside cells, but
in the magnitude of the potential may range from - 30 mV to - 90 mV.
Thus, the concentration gradient always favours chloride movement into cells but
the resting electrical potential always favours chloride movement out of cells.
The balance between the two forces will determine the direction of chloride
movement.
 If the chloride concentration is high inside the cell, the concentration gradient for
chloride will be small and the effect of the electrical potential is likely to
predominate.
 In this case, chloride will move out of the cell, depolarizing the cell membrane,
i.e. reducing the inside negative electrical potential.
 On the other hand, if the chloride concentration inside the cell is small, there will
be a large concentration gradient and it will probably overwhelm the electrical
potential, resulting in chloride movement into cells, thereby hyperpolarizing the
cell membrane, i.e. increasing the magnitude of the negative membrane potential.
What
Chloride
Channels
Do for a
Cell ?

11. References
Book: Bruce Alberts, Alexander Johnson, Julian
Lewis, Martin Raff, Keith Roberts, Peter Walter,
Molecular biology of the cell, 5
th
Edition.
Akabas, Myles. (2005). Chloride Channels.
10.1038/npg.els.0004061.

12. Thank You
Please do Like and
Subscribe
My Channel…!!