2. 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
3. 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
Viscosity
Surface Tension
6. Lets Recap from Chemistry…
3 particle states of matter
Diffusion
What is the particle
arrangement and motion?
Solid Liquid Gas
7. Diffusion
Definition:
The net movement of particles
from a region of higher concentration
to a region of lower concentration,
down the concentration gradient.
High concentration Low concentration
14. Equilibrium
When particles reaches an equilibrium, does the particles
stop moving?
Hint: Particles move in a random and dynamic motion.
15. Concentration Gradient
The concentration difference between regions of high
concentration and low concentration.
High concentration
gradient
Down the
concentration gradient
Low
concentration
gradient
17. Concentration Gradient
The steeper the concentration gradient, the faster
diffusion takes place
Steeper concentration gradient
Fast rate of
diffusion
Less steep concentration gradient
Slow rate of diffusion
18. Which graph will result in the
fastest rate of diffusion?
A B
C D
19. Factors that affects the rate of
substance movement…
Cross-sectional area through which diffusion occurs
Temperature
Molecular weight of a substance
Distance through with diffusion occurs
Concentration gradient
20. Examples
Movement of
substances in and
out of amoeba cells
Movement of CO2
and O2 in and out of
lung cells
Movement of
nitrates in and
out of root hair
cells
21. Movement of Substances
Diffusion Osmosis
Net movement of particles
from a region of high
concentration to a region
of low concentration,
down the concentration
gradient.
includes
definition
Key Ideas:
1) Liquid/ Gas particles move
from region of high concentration
to low concentration
2) Movement of particles is
random and dynamic in
equilibrium (net)
3) Concentration gradient
4) Examples of diffusion
23. Osmosis
Definition:
The movement of water molecules
through a partially permeable membrane
from a solution of high water potential,
to a solution of lower water potential.
Partially permeable
membrane
: sucrose
:water
molecules
24. Partially
Permeable Membrane
Permeable
Membrane
•Allows both the solvent
(water) and the solutes (
dissolved substances to
pass through)
•Equal concentration of all
ions in both sides of the
membrane.
•Eg: Cell Wall of plant cells
•Allows some substances to pass
through but not others.
•Unequal concentration of ions in both
sides of the membrane
•Eg: Cell membrane in plant and animal
cells.
25. The movement of water molecules through a
Partially permeable
membrane
: sucrose
:water
molecules
partially permeable membrane
•Only water molecules passes through the partially permeable
membrane (sucrose solution too big to pass through the partially
permeable membrane).
26. Water Potential
Water potential is the measure of the tendency of
water to move from one place to another.
Dilute Solution: High water potential
Concentrated Solution: Low water potential
Same concentration: Equal water potential
Water potential Gradient:
Water molecules move from a high water potential to a
lower water potential.
27. From a solution of high water potential, to a solution
of lower water potential.
•Only water molecules passes through the partially permeable
membrane (sucrose solution too big to pass through the partially
permeable membrane).
: sucrose
:water
molecules
Partially permeable
membrane
High water
potential
Low water
potential
Movement of water molecules
28. From a solution of high water potential, to a solution
•Only water molecules passes through the partially permeable
membrane (sucrose solution too big to pass through the partially
permeable membrane).
: sucrose
:water
molecules
of lower water potential.
Partially permeable
membrane
Raised water level
29. Hypotonic Vs Hypertonic
Higher water potential compared to _____/ Lower water potential compared to ____
: sucrose
:water
molecules
Used to compare 2 solutions.
Hypotonic to ____ / Hypertonic to _____.
*Isotonic: Same water potential
x y
High concentration of
sucrose : Low water
potential
X is Hypotonic compared to y
Low concentration of
sucrose : High water
potential
Y is Hypertonic compared to x
30. Osmosis in living organisms
Plant Cells Animal
Cells
Plant cell behaves differently from animal cell
when placed in solutions with differing water
potentials.
•Due to presence of cell wall in plants.
31. Osmosis in plant cell
Fully permeable: allows most
dissolved substances to pass
through
Cell surface membrane is a
partially permeable membrane
32. Plant cell in
High water potential
1. Cell vacuole has lower
water potential compared to
solutions outside cell
2. Water enters cell by
osmosis.
3. Vacuole increases in size,
pushes against cell wall
4. Cell wall exerts opposing
pressure (against turgor
pressure)
5. Plant cell expands and
become turgid (cell does
not bursts) Turgor
33. Why is turgor important?
Maintain the shape of soft tissues in plants
Able to remain firm and erect because of turgor pressure.
High rate of evaporation of water from cells.
Lose turgidity and will wilt.
Movement of plant parts
Flowers open during the day and close at night
Changes in the turgidity of the plants on the opposite
surfaces of the petals
Mimosa plants
Opening and closing of stomata due to changes in
turgidity in guard cells.
34. When conditions are conducive to stomatal opening (e.g.,
high light intensity and high humidity), a proton
pump drives protons (H+) from the guard cells. This means
that the cells' electrical potential becomes increasingly
negative. The negative potential opens potassium voltage-gated
channels and so an uptake of potassium ions (K+)
occurs. To maintain this internal negative voltage so that
entry of potassium ions does not stop, negative ions
balance the influx of potassium. In some cases, chloride
ions enter, while in other plants the organic ion malate is
produced in guard cells. This increase in solute
concentration lowers the water potential inside the cell,
which results in the diffusion of water into the cell
through osmosis. This increases the cell's volume
and turgor pressure. Then, because of rings of
cellulose microfibrils that prevent the width of the guard
cells from swelling, and thus only allow the extra turgor
pressure to elongate the guard cells, whose ends are held
firmly in place by surrounding epidermal cells, the two
guard cells lengthen by bowing apart from one another,
creating an open pore through which gas can move.
An open stoma (a)
and a closed stoma
(b)
1 Epidermal cell
2 Guard cell
3 Stoma
4 K+ ions
5 Water
6 Vacuole
35. When the roots begin to sense a water shortage
in the soil, abscisic acid (ABA) is
released.[6] ABA binds to receptor proteins in
the guard cells' plasma membrane and cytosol,
which first raises the pH of the cytosol of the
cells and cause the concentration of free
Ca2+ to increase in the cytosol due to influx
from outside the cell and release of Ca2+ from
internal stores such as the endoplasmic
reticulum and vacuoles.[7] This causes the
chloride (Cl-) and inorganic ions to exit the
cells. Second, this stops the uptake of any
further K+ into the cells and, subsequently, the
loss of K+. The loss of these solutes causes an
increase in water potential, which results in the
diffusion of water back out of the cell
by osmosis. This makes the cel lplasmolysed,
which results in the closing of the stomatal
pores.
An open stoma (a) and a
closed stoma (b)
1 Epidermal cell
2 Guard cell
3 Stoma
4 K+ ions
5 Water
6 Vacuole
36. Plant cell in
Low water potential
1. Vacuole has higher water
potential compared to
solution outside cell.
2. Water leave cells by osmosis
3. Vacuole decreases in size
4. Cytoplasm shrinks away
from cell wall ( Plasmolysis.)
Can be restored to original
state. How?
37. Plasmolysis
Causes tissue to be limp or flaccid
Cells will be killed if remain plasmolysed too long
Not advisable to add too much fertilisers. Why?
How to reverse this?
38. Osmosis in living organisms
Plant Cells Animal
Cells
Plant cell behaves differently from animal cell
when placed in solutions with differing water
potentials.
•Due to presence of cell wall in plants.
39. Animal cell in
High water potential
1. Cytoplasm has lower
water potential
compared to solution
outside cell
2. Water enters by
osmosis
3. Animal cell will swell
and may bursts as
it does not have a
cell wall to protect it.
40. Animal cell in
Low water potential
1. Cytoplasm has higher
water potential
compared to the
solution outside the
cell.
2. Water leaves by
osmosis
3. Cell shrinks and little
spikes appear on cell
surface membrane.
(Crenation)
43. Factors that affects the rate of
diffusion…
Concentration/Water potential Gradient
Cross-sectional area through which diffusion occurs
Temperature
Molecular weight of a substance
Distance through with diffusion occurs
44. Why do you think cells are so
small???
Why most large organisms are
multi-cellular and not
unicellular?
45. Surface Area to Volume Ratio
Affects rate of movement of substances across cell
surface membranes.
“The greater the surface area of cell surface
membrane to per unit of volume, the faster the rate
of diffusion of a substance for a given
concentration gradient.”
???
46. Surface area to volume ratio
Which one has a bigger surface area?
47. Surface area to volume ratio
The larger the surface area to volume ratio, the faster
the rate of substance movements.
Cells adaptations for better absorption of materials.
(increased surface area)
Root hair cells
Epithelial cells of small intestine
Red blood cells
48. Movement of Substances
Diffusion Osmosis
Active
Transport
Net movement of particles
from a region of high
concentration to a region
of low concentration,
down the concentration
gradient.
includes
definition
Key Ideas:
1) Liquid/ Gas particles move
from region of high concentration
to low concentration
2) Movement of particles is
random and dynamic in
equilibrium (net)
3) Concentration gradient
4) Examples of diffusion
definition
The movement of water
molecules through a
partially permeable
membrane from a
solution of high water
potential, to a solution of
lower water potential.
Key Ideas:
Opposites!
1) Only water molecules
2) Partially permeable membrane
3) High water potential to low
water potential
4) Hypertonic & hypotonic
5) Osmosis in living cells
6) SA to Vol ratio
7) Adaptations
49. Movement of Substances
Diffusion Osmosis Active
Transport
Net movement of particles
from a region of high
concentration to a region
of low concentration,
down the concentration
gradient.
includes
definition
Key Ideas:
1) Liquid/ Gas particles move
from region of high concentration
to low concentration
2) Movement of particles is
random and dynamic in
equilibrium (net)
3) Concentration gradient
4) Examples of diffusion
definition
The movement of water
molecules through a
partially permeable
membrane from a
solution of high water
potential, to a solution of
lower water potential.
Key Ideas:
1) Only water molecules
2) Partially permeable membrane
3) High water potential to low
water potential
4) Hypertonic & hypotonic
5) Osmosis in living cells
6) SA to Vol ratio
7) Adaptations
definition
Energy is used to move
particles against
concentration gradient (
from a region of low
concentration to a
region of higher
concentration) , up a
concentration gradient.
Key Ideas:
1) Requires energy
2) From low to high
3) Only in living cell
4) Active transport in
living cells
Editor's Notes
*Temperature The higher the temperature the higher the rate of diffusion. *Presence of organic solvents They dissolve the phospholipid bi-layer allowing more substance out. A high amount of organic solvent will break the membrane down completely. *Concentration gradient The larger the difference in concentration of a substance in and out of a cell the higher the rate of diffusion. *Membrane thickness The thinner the membrane the higher the rate of diffusion because the molecules have less of a distance to travel. *pH The more extreme the pH the less the amount of large and polar molecules and ions pass the membrane as the pH denatures the specific shape of the carrier and channel proteins. *Surface area available The more surface area compared to volume the higher the rate of diffusion. *More ATP production More active transport so more molecules moved from lower concentration to higher concentration. *Respiratory inhibitor present like cyanide Less active transport.
The leaves also close under various other stimuli, such as touching, warming, blowing, or shaking. These types of movements have been termed seismonasticmovements. The movement occurs when specific regions of cells lose turgor pressure, which is the force that is applied onto the cell wall by water within the cell vacuoles and other cell contents. When the plant is disturbed, specific regions on the stems are stimulated to release chemicals including potassium ions which force water out of the cell vacuoles and the water diffuses out of the cells, producing a loss of cell pressure and cell collapse; this differential turgidity between different regions of cells results in the closing of the leaflets and the collapse of the leaf petiole.
