Transcript An Introduction to Med. Biophysics - Lectures For UG-5

Introduction to biophysics
Course Plan
Course Contents
Diffusion
Osmosis
What is “Biophysics”
Biophysics is a specialized sub area of biology
It is the science of physical principles of life itself and of
biological systems. Biophysics is an interdisciplinary
science that explains the laws and principles of physics
which govern various biological processes. Biophysics
spans all levels of biological organization from molecular
scale to whole organism
Course Plan
 Quiz/Assignments: 15-20 marks
 Sessionals: 30-35 marks
 Terminal: 50 marks
Course Contents
 Introduction to biophysics
 Forces governing biological processes
 Energetics and dynamics of biological systems
 Biomechanics
fluid flow, blood circulation, muscle contraction,
lever system of the body etc
 Membrane physics
Course Contents
 Electrical properties of cells
Nerve Signals, nerve impulses, cardiac cycle and
electrocardiography (ECG)
 Physics of five senses
sense of sight, hearing, taste, touch and smell
 Physical factors of the environment
Temperature, pressure, mechanical oscillations
(vibrations, sound, hearing), electromagnetic
fields in the environment
Books & Good Websites
1. http://www.physicsclassroom.com/
2. http://highered.mcgraw-
hill.com/sites/0072495855/student_view0/
Books:
 Human Physiology: From Cells to Systems By
Lauralee Sherwood
 Fundamentals of Human Physiology By Lauralee
Sherwood
Good Books
 Biophysics
 An Introduction to Med.
Biophysics by Prakash
 Books Available at CAMP, NUST
 Advanced Biophysics by S. K. Agarwal
 Basic Biophysics –For Biologist- by
M.Daniel
 Biological activities happening in different organs of
living body like kidney, liver, heart, lungs as well as
those in intracellular and extracellular biological fluid
are governed by fundamental laws of physics namely
 Diffusion
 Osmosis
 Surface Tension
 Viscosity
Membrane Transport
 There are two types of transport mechanisms
occurring in cells
1.
Active transport
2.
Passive transport
We will focus mainly on passive mode of transport
Passive transport
 Molecules that can penetrate the plasma membrane
on their own that is unassisted (without consuming
cell energy) are passively driven across the membrane
by two forces
1. Diffusion: down the concentration/chemical
gradient
2. Conduction along an electric gradient
Diffusion
 Molecules are in continuous random motion
(Brownian motion)
 Evident mostly in liquids and gases whose
molecules are free to move
 Greater the concentration of molecules greater the
likelihood of collision and movement to chamber
with low concentration
Importance of diffusion
 Transfer of nutrients to body cells from blood stream
 Transport of oxygen into cells of organs and to drive
carbon dioxide out of them e.g lungs, eyes
Importance of diffusion in eye
 The cornea is unusual in that it is transparent. The tissues that make
up the cornea are able to maintain their transparency partly by not
having blood vessels flowing through them.
 Without blood vessels the cornea must get it's Oxygen directly from
the air. The oxygen first dissolves in the tears and then diffuses
throughout the cornea to keep it healthy. Equally important, the waste
product carbon dioxide diffuses out of the cornea and into the
atmosphere in the reverse process
Diffusion of gases in lungs
 Exchange of gases across the alveolar
membrane takes place due to
diffusion
 The blood carried to lungs is low in
O2, having given up O2 to the body
tissues for cellular metabolism while
the air in alveolus is rich in oxygen
 Because of
this concentration
gradient, oxygen diffuses into the
blood
 Similarly CO2 diffuses out of the
blood into alveolus
Absorption of drugs
 Diffusion enables absorption of drugs across a
biological barrier (layers of cells, cell membranes etc)
into the bloodstream administered through any mean
except for intravenous administration
 For example, transport of medicine from transdermal
patch to skin and then into bloodstream occurs by
passive diffusion
Osmosis
 The spontaneous passage of solvent from a solution of lower
concentration towards a solution of higher concentration when the
two are separated by a semi permeable membrane is called osmosis
 Osmosis is a special case of diffusion. It involves the diffusion of water
through the semi permeable membrane to equalise the concentration
of solutions on its two sides
Osmosis in fresh and sea water
fish
Fresh water trout
Sea water Herring
wilting
These cells are short of water; the
tissue is limp and the plant is wilting
Turgid plant
The cells have taken up water by
osmosis; the cells are turgid and the
tissue is firm
25
Growth in a shoot tip
these cells will divide
cell division
continues
vacuoles
forming
cells absorb
water by
osmosis and
expand
Effect of different solutions on
blood cells