ion channel and carrier protein By KK Sahu Sir

INTRODUCTION �- DEFINITION OF ION CANALS�- HISTORY AND DIVERSITY OF ION CANALS�- CARRIER PROTEIN-DEFINITION� - CLASSES OF CARRIER PROTEIN � - MECHANISM OF ION CANALS AND CARRIER PROTEIN � - MEMBRANE TRANSPORT�- BIOLOGICAL ROLE OF ION CANALS AND CARRIER PROTEIN� - CONCLUSION �- REFERENCE

1. ION CANALS AND CARRIER PROTEIN
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. CONTENTS:
-INTRODUCTION
-DEFINITION OF ION CANALS
-HISTORY AND DIVERSITY OF ION CANALS
-CARRIER PROTEIN-DEFINITION
-CLASSES OF CARRIER PROTEIN
-MECHANISM OF ION CANALS AND CARRIER PROTEIN
-MEMBRANE TRANSPORT
-BIOLOGICAL ROLE OF ION CANALS AND CARRIER PROTEIN
-CONCLUSION
-REFERENCE

3. INTRODUCTION:
“Ioncanalsareporeformingproteinthathelp
establishandcontrolthesmallvoltagegradient
acrosstheplasmamembraneofcell.
Carrierproteinareproteinwhichareinvolvedinthe
movementofions,smallmoleculesormacro
molecules.”

4. ION CANALS-
1.Definition-
“Whenionsrushincellmembrane-cellrhythmdepends
ontheopeningandclosingofacomplexseriesofvalves
onthecellmembrane,calledioncanals.”
Somevalvesletcertainionslikepotassium(K+)flow
out,othersletdifferentionslikesodium(Na+)flowin.
Therearealsopumpsthatactivelymoveionsone
directionoranother.

5. 2.Diagram showing Ion canals
process-

6. Schematicdiagramofanioncanal-
. 1–canalsdomains(typicallyfourpercanals),
2-outervestibule,
3-selectivityfilter,4-diameterofselectivityfilter,
5-phosphorylationsite,6-cellmembrane.
Diagram showing Ion canals:

7. 3. HISTORY-
The fundamental properties of currents mediated by ion
canals were analyzed by British biophysicist Alan
Hodgkin and Andrew Huxley as part of their Nobel prize –
winning research on the action potential ,published in
1952.
The existence of ion canals was confirmed by Bernard
Katz in 1970.

8. 4.Diversity-
There are over 300 types of ion channels in a
living cell. Ion channels may be classified by the
nature of their gating, the species of ions passing
through those gates, the number of gates (pores)
and localization of proteins.

9. 5.Some example of ion canals-
(1.) Voltage gated Calcium canals-This family contains
canals and are equally large these canals play an important
role in both linking muscle excitation with contraction as
well as neuronal excitation with transmitter release
(2.) Voltage gated proton canals–This is open with
depolarization ,but in a strongly pH –sensitive manner .The
result is that these canal open only when the
electrochemical gradient is outward, such that their
opening will only allow when protons leave cell.

10. (3.)chloride and potassium canal chloride is most
abundant anion ,and hence they are known as chloride
canal.
Potassium canal-voltage gated ,calcium-activated
inward –rectifier.

11. CARRIER PROTEIN-
“Carrier proteinsare proteins which are
involved in the movement of ions , small
molecules , or macro molecules , such as
another protein , across a biological
membrane” .
Carrier proteins are integral membrane
proteins; that is they exist within and span the
membrane across which they transport
substances.
.

12. The proteins may assist in the movement of substances
by facilitated diffusion or active transport. These
mechanisms of movement are known as carrier
mediated transport.
Each carrier protein is designed to recognize only one
substance or one group of very similar substances

13. 1. Classes of Carrier Proteins:
Uniport-(facilitated diffusion) carriers mediate
transport of a single solute.e.g.-GLUT1 glucose
carrier. theglucose-Na
+
symportfound in plasma
membranes of some epithelial cells
the bacterial lactose permease, a H
+
symportcarrier
Symport-carriers bind two dissimilar solutes
(substrates) and transport them together across a
membrane.E.g.-bacterial permease
Antiport-(exchange diffusion) carriers exchange one
solute for another e.g.-adenine nucleotide translocase

14. 2.Diagram showing classes of carrier
protein -

15. Mechanism of ion canals And Carrier
protein-
Active transport-The action of the sodium –
potassium pump is an example of primary active
Transport. Active transport is the movement of a
substance across a membrane against its
concentration gradient .
This is usually to accumulate high concentration of
molecules that a cell needs , such as glucose or
amino acids. When the lipid bilayeris
impermeable to the molecule needing transport
,active transport is also necessary.

16. Diagram showing Active transport-

17. FacilitatedDiffusion-
“ Facilitated diffusion is the passage of molecules or
ions across a biological membrane through specific
carrier proteins and requires no energy ”.
Facilitated diffusion is used especially in the case of
large polar molecules and charged ions; once such
ions are dissolved in water they cannot diffuse freely
across cell membranes due to the hydrophobic
nature of the fatty acid tails of the phospholipids that
make up the bilayers.

18. The type of carrier proteins used in facilitated
diffusion is slightly different than in active transport.
They are still transmembranecarrier proteins, but
these are gated transmembranecanals, meaning
they do not internally translocate, nor require ATP
to function.
The substrate is taken in one side of the gated
carrier, and without using ATP the substrate is
released into the cell

19. Diagram showing Facilitated Diffusion-

20. Pathology-
A number of inherited diseases involve defects in carrier
proteins in a particular substance or group of cells.
Cysteinuria( cysteinein the urine) is such a disease
involving defective cysteinecarrier proteins in the kidney
cell membranes.
This is one cause of urinary stones.Somevitamin carrier
proteins have been shown to be overexpressedin patients
with malignant disease. For example, levels of riboflavin
carrier protein (RCP) have been shown to be significantly
elevated in people with breast cancer.

21. Membrane transport-
(1.)Introduction -Transport of two general classes: carrier
and channel .These are exemplified by two
ionophoree.g.-a carrier (Valinomycin) and a
channel(gramicidin)

22. (2)Conformation changes-
Ion canals and carrier proteins are responsible for
conformational changes of plasma membrane. Carrier proteins
cycle between conformations in which a solute binding site is
accessible on one side of the membrane or the other. There
may be an intermediate conformation in which a bound
substrate is inaccessible to either aqueous phase.

23. Diagram showing conformation
changes in plasma membrane-

24. Control of ion canal and carrier
protein mechanism-
Ion canal and carrier proteins are control by
allostericregulation .conformation changes
associated with channel opening may be regulated
by one of the following:
1.Voltage
2.Binding of a ligand
3.Membrane strech

25. (1)canalsareespeciallyprominentcomponentsofthe
nervoussystem.
(2)mostoftheoffensiveanddefensivetoxinsthat
organismshaveevolvedforshuttingdownthe
nervoussystemsofpredatorsandprey(e.g.-venoms
producedbyspiders,scorpions,snakes,fish,bees,
seasnailsandothers)workbymodulatingioncanals
conductance.
(3)someofthebiologicalprocessisconductbyion
canalssuchascardiac,skeletal,andsmoothmuscle
contraction.sotheioncanalsandcarrierprotein
havingmoreusefulbiologicalroleforbiological
processes.
Biological role Of Ion Canals and Carrier Protein-

26. Conclusion-

27. REFERENCE
1.Advanced biology-Kent michael
2.Cell and molecular Biology-Gerald Karp
3.Cell and molecular Biology-P.K.Gupta
Websites:
www.kbiotech.com
www.wikipedia.com