This PPT for all Medicos and Non medical Students for better understanding of Transport across cell membrane

1. TRANSPORT ACROSS CELL
MEMBRANE

2. Introduction
Cell membrane structure & water
distribution
History
Comparative
Types of transport (classification)
Applied

5. HISTORY
Osterhout (1933)
First speculated the idea of carrier mediated
transport
S.J.Singer & G.L.Nicholson(1972)
Discovered the cell membrane structure.
Erwin Neher & Bert sakmann (Germany)
Received Nobel prize in 1991 for the work on
single ion channel.

6. Dr.Overtone
Postulated the “lipid theory” of
transport across cell membrane.
Traube;
Postulated the “surface tension theory
of transport across the membrane”.

7. WATER CONTENTS OF DIFFERENT ORGANISMS
Name of organism % of body weight
Chicken 74
Cockroach 61
Codfish 82
Earthworm 80
Frog 78
Jellyfish 95
Lobster 79
Fate Pig 40

8. Transport
across cell
membrane
Micro molecular
Active
Transport
Passive
Transport
Macromolecular
Exocytosis Endocytosis

9. Diffusion
Simple
diffusion
Through
lipid
bilayer
Through
membrane
channel
Leak
channel
Gated
channels
Voltage Ligand
Stretch
Activated
Osmosis
Ultra
filtration
Faciliated
diffusion

10. Active
Transport
Primary
active
transport
Secondary
active
transport
Co-
transport
Counter-
transport

11. Macromolecular
Transport
Endocytosis
-Phagocytosis
-Pinocytosis
Exocytosis
-Emiocytosis
-Reverse
Phagocytosis

12. DIFFUSION
 Random continuous movement of molecules of a
substance among one another due to their kinetic
energy in liquid or gas state.

13. Diffusion is classified as:
1) Simple Diffusion
2) Facilitated Diffusion

14. SIMPLE DIFFUSION
Diffusion of substance by itself without the
help of carrier protein. [through a membrane
opening intermolecular spaces.]
 Simple Diffusion through lipid bilayer.
Only liquid soluble substance can pass through
it.
e.g. alcohol, ether,O2 ,CO2. etc.
o Simple Diffusion through membrane channel

16. Gating of protein channels
 Gates are flap like extension of protein
molecules which can open or close the channel
1) Voltage gated channels:- Gates are open or
close in response to change in voltage across
cell membrane. Na⁺ and K⁺ channel.
2) Chemical gating :- Open in response to
chemicals.
e.g. Effect of Ach on Ach channel
3) Stretch activated channel :- In response to
mechanical stretch of membrane.

18. FACTOR AFFECTING THE RATE OF SIMPLE
DIFFUSION
Directly proportional to concentration
gradient
Lipid solubility
Surface area of membrane
Thickness of membrane
Molecular weight
Temperature
No.of channel per unit area of membrane
 Diffusion coefficient P* A
Where P- Permeability
A- Area

19. FACILITATED DIFFUSION
Diffusion of a substance from an area of
high conc. to an area of low conc. with
the help of carrier protein.
Features:-
Substance which can not pass through
lipid bilayer or channels and larger in size
are transport by this mechanism e.g.
Glucose, amino acid, fructose.
Substance always transport down to
concentration gradient
No energy required
Specificity

20. Saturation kinetics i.e. V max

21. Subjects to competitive inhibition e.g.
Glucose
Certain hormones can accelerate or
inhibit process e.g. insulin increase the
activity of glucose transports

23. NET DIFFUSION
It is net movement of molecule of
substance (liquid or gas) from an area of
high conc. to an area of low conc. due to
their kinetic energy along conc. electrical
or pressure gradient.
Factors affecting ‘Net rate’ of diffusion
Concentration difference
Electrical potential across membrane.
Pressure difference

24. Effect Of Concentration Difference on net
diffusion

26. Effect of Membrane Electrical Potential On
Diffusion Of Ions

28. Effect Of Pressure Difference Across The
Membrane

29. OSMOSIS
Osmosis is defined as net movement of molecules of
solvent from an area of low solute concentration to
an of high solute concentration across a semi
permeable membrane.

30. OSMOTIC PRESSURE:-
Pressure required to be applied on the solution
of high concentration to stop or prevent osmosis.
It is pulling pressure

31. ACTIVE TRANSPORT
 It is transport of substance from an area of low
conc. to an area of high conc. with help of
carrier protein.
 It occurs against conc.gradient,electrical
gradient, pressure gradient.
 Energy is always required.
 Carrier protein is specific but can transport
more than one substance.

32. PRIMARY ACTIVE TRANSPORT
 A type of active transport in which energy for
transport is directly derived from breakdown
of ATP and carrier protein itself has ATP ase
activity.
 e.g. Na+_ K+pump, Ca+ pump, iodide pump , H+-
K+ pump.

33. Na+- K+ PUMP
 Na+-K+ pump present in all cells of body.
 It is responsible for maintaining the Na+ & K+
conc. difference across the membrane creating
electro negativity inside the cell membrane.
 It is complex protein made up two subunits α &
β .
 α subunit ;It is large catalytic substance with
molecular weight 10,0000.
 It has three Na+ binding site on internal surface
& two K+ binding site on external surface.
 Β subunit; It is small glycoprotein molecular
weight 55000.

34. Na+- K+ PUMP

35. FUNCTIONS
 Maintain conc. difference of Na+ & K+ across the
cell membrane which is essential for RMP & AP &
excitability.
 It act as electrogenic pump-produce negativity
inside the cell & coupling ratio is 3:2
 Controls cell volume by keeping out osmotic ally
active Na+ ions from the cell.
 It provides energy for secondary active transport of
substance like glucose.
 It is important in heat production & metabolism.

36. FACTORS AFFECTING NA+ PUMP
 Na+ conc. Inside the cell activates.
 Thyroid hormone, aldesterone, insulin activate
 Oxygen lack -inhibit
 Digitalis -inhibit
 Ouabain -inhibit
 Fall in temp.- inhibit.

37. SECONDARY ACTIVE TRANSPORT
 A type of transport in which energy is directly derived
from ionic conc. gradient created by primary active
transport;
 It has two types :
-Co-transport
-Counter-transport

38. CO-TRANSPORT
Two or more substances move in the same
direction across the cell membrane created by
primary active transport.
e.g. Na co-transport of glucose & amino acids in
epithelial cells of intestinal tract &renal tubules.

39. COUNTER TRANSPORT
 Two substance transport in opposite direction
 e.g.Na+-H counter transport in proximal tubules of
kidney.
 Na-Ca counter transport

40. Inhibitors of Active Transport
 Active transport get inhibited by inhibitors of
ATPase e.g. Digitalis[inhibit Na-ATPase in
cardiac muscle.]
 Omeprazole inhibits H K ATPase in gastric
parietal cell.
 Active transport may be inhibited
nonspecifically by dinitrophenol which
uncouples oxidation & phosphorylation in
biological oxidation.
 Cyanide inhibit electron transport chain.
 Fluoride or iodoacetate which inhibit anaerobic
glycolysis.

41. MACROMOLECULAR TRANSPORT
 Endocytosis is concerned with taking the
material inside cell membrane.

42.  Endocytosis is classified as;
 Phagocytosis ; large particles such as bacteria, cells or
part of degenerating tissues are ingested.
 Pinocytosis;small vesicles are ingested.

43. Exocytosis; is concerned with throwing the
material outside the cell.
Exocytosis is classified as:
-Emiocytosis
-Reverse phagocytosis

44. APPLIED PHYSIOLOGY
Channelopathies
Mutation in ion channel causes variety of
channelopathies mostly affect muscle & brain
tissue presenting episodic paralysis &
convulsions.
Study of channel distribution
Tetradotoxin(TTX) & Saxitoxin(STX) are toxins
that bind to the Na channels & block them .
TTX & STX can be used to determine the no. &
distribution of Na channel.

45. Increasing cardiac contractility in failing
heart .
e.g. Cardiac glycoside like digitalis
Bind and inhibit Na⁺ and K⁺ pump
Na⁺ accumulation inside the cell
Ca⁺ accumulation inside the cell
Increased myocardial contractility

46. REFRENCES
 1.Text book of medical physiology
-Guyton and hall, 12th edition.
 2.Ganong’s review of medical physiology
-23rd edition
 3.text of medical physiology
-2nd edition
 4.net sources (acknowledge for all online sources)
 5.text book of medical physiology
--A.K. JAIN
 6.text book of medical physiology
---indu khurana


47. THANK YOU . . .