MEMBRANE PHYSIOLOGY. ARJUN MAITRA Asst. Professor Dept. of Physiology. LECTURE SLIDES FROM THE CLASSES TAKEN DURING 2008-09 SESSION. Topic: Cell membrane & Transport across the membrane Lecture taken for Courses: MBBS,BPT Useful for: B.ScNursing& others.
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Dept. of Physiology
Topic: Cell membrane & Transport across the membrane
Lecture taken for Courses: MBBS,BPT
Useful for: B.ScNursing& others
HERE I HAVE TRIED TO SIMPLIFY THE HUGE SUBJECT WITH ANIMATIONS,
DIAGRAMS, FLOW CHARTS & RELEVENT MCQs.
DIFFERENT TEXT BOOKS AND REFERENCE BOOKS HAVE BEEN USED FOR
PREPARING THE CONTENTS.
REMEMBERTHESE SLIDES ARE NOT THE SUBSTITUTE OF YOUR TEXT BOOKS
ANIMATIONS AND DIAGRAMS ARE COLLECTED FROM DIFFERENT WEBSITE
SOLELY FOR EDUCATION PURPOSE.
outside the cell
interior of cell
Protecting the cell surface from mechanical and chemical damage
Lymphocyte stained with ruthenium red
Diffusion: random movement of particles from an area of high concentration to an area of low concentration.
(High to Low
J = - DA(DC/DX)
J is the net rate of diffusion,
D is the diffusion coefficient, D = - ½b2f
A is the area, and Δc/Δx is the concentration gradient.
The minus sign indicates the direction of diffusion.
TYPICAL VALUES OF THE DIFFUSION COEFFICIENT
• Diffusion is the random mixing of particles that occurs
in a solution as a result of the kinetic energy of the
• Diffusion rate across plasma membranes is influenced
by several factors:
– Steepness of the concentration gradient
– Size or mass of the diffusing substance
– Surface area
– Diffusion distance
diffusion of specific particles through transport proteins found in the membrane
Mediates passive transport
Change is spontaneous and random, so dependent on concentration
General principles I
General principles II
Permeability coefficient (cm/sec)
PRIMARY ACTIVE TRANSPORT SECONDARY ACTIVE TRANSPORT
An active transport pump may be a uniporter or antiporter.
ABC (ATP binding cassette) transporters, which catalyze transmembrane movements of various organic compounds including amphipathic lipids and drugs, will not be discussed here.
It catalyzes ATP-dependent transport of Na+ out of a cell in exchange for K+ entering.
It catalyzes transport of H+ out of the gastric parietal cell (toward the stomach lumen) in exchange for K+ entering the cell.
Some evidence indicates that these pumps are antiporters, transporting protons in the opposite direction.
Ca++-ATPase pumps function to keep cytosolic Ca++ low, allowing Ca++ to serve as a signal.
P-type transport ATPase (dependent on phosphorylation)
Alpha Subunit 100,000
Beta Subunit 55,000
NSF =N-ethylmaleimide-sensitive factor
SNAP = soluble NSF attatchment protein
EK = -75mV
A new approach to quantify the contribution of different ions
PERMEABILITY RATIO (At Rest) PK : P Na : P Cl = 1.0: 0.04 : 0.45
(At peak of Action Potential) PK : P Na : P Cl = 1.0 : 20 : 0.45
Voltage gated Slow
Voltage Gated Fast
Inward Rectifier Channel
CONCEPT OF FIRST & SECOND MESSENGER SYSTEM
SECOND MESSENGERS ARE INTRACELLULAR MEDIATORS
FROM FIRST MESSENGER TO THE SECOND MESSENGER
MESSENGER / LIGAND
TRANSLATE A SIGNAL
TO A BIOLOGICAL EFFECT
SMALL G PROTEINS
HETEROTRIMERIC G PROTEIN
G proteins were discovered by Alfred G. Gilman and Martin Rodbell
For this discovery they won the 1994 Nobel Prize in Physiology or Medicine.
Alpha bound to GDP
bg acts as activator
Alpha has intrinsic