BCH 504

Analytical and Biochemical

Techniques

(2+1)

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

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

Movement of Substances

Diffusion Osmosis

Diffusion

Lets Recap from Chemistry…3 particle states of matter

Solid Liquid Gas

Diffusion

What is the particle

arrangement and motion?

Definition:

The net movement of particles

from a region of higher concentration

to a region of lower concentration,

down the concentration gradient.

Diffusion

High concentration Low concentration

Diffusion in liquid state

: Ink dye

: Water

molecules

Diffusion in liquid state

: Ink dye

: Water

molecules

Diffusion in gaseous state

: Perfume

molecules: Air

molecules

Diffusion in gaseous state

: Perfume

molecules: Air

molecules

Net Movement

Note: This barrier

does not illustrate a

partially permeable

membrane.

Net Movement

EquilibriumWhen particles reaches an equilibrium, does the particles

stop moving?

Hint: Particles move in a random and dynamic motion.

The concentration difference between regions of high

concentration and low concentration.

Concentration Gradient

High concentration

gradient

Low

concentration

gradient

Down the

concentration gradient

Concentration Gradient

Which slide will allow you to go down faster?

A

B

Answer: A

The steeper the concentration gradient, the faster

diffusion takes place

Fast rate of

diffusion

Steeper concentration gradient

Concentration Gradient

Less steep concentration gradient

Slow rate of diffusion

Which graph will result in the

fastest rate of diffusion?

A B

C D

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

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

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

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

Key Ideas:

Osmosis

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.

: sucrose

:water

molecules

Partially permeable

membrane

Partially

Permeable MembranePermeable

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.

: sucrose

:water

molecules

Partially permeable

membrane

The movement of water molecules through a partially permeable membrane

•Only water molecules passes through the partially permeable

membrane (sucrose solution too big to pass through the partially

permeable membrane).

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.

: 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).

High water

potentialLow water

potential

Movement of water molecules

From a solution of high water potential, to a solution of lower water potential.

: sucrose

:water

molecules

Partially permeable

membrane

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).

Raised water level

Hypotonic Vs Hypertonic

: sucrose

:water

molecules

High concentration of

sucrose : Low water

potential

Low concentration of

sucrose : High water

potential

X is Hypotonic compared to y

x y

Y is Hypertonic compared to x

Used to compare 2 solutions.

Hypotonic to ____ / Hypertonic to _____.Higher water potential compared to _____/ Lower water potential compared to ____

*Isotonic: Same water potential

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.

Osmosis in plant cellFully permeable: allows most

dissolved substances to pass

through

Cell surface membrane is a

partially permeable membrane

Plant cell in

High water potential1. 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

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.

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

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

Plant cell in

Low water potential1. 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?

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?

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.

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.

Animal cell in

Low water potential1. 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)

What if cell placed in isotonic

solution?

lol

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

Why do you think cells are so

small???

Why most large organisms are

multi-cellular and not

unicellular?

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.”

???

Surface Area to Volume Ratio

Which one has a bigger surface area?

Surface area to volume ratio

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

Movement of Substances

Diffusion OsmosisActive

Transport

Net movement of particles

from a region of high

concentration to a region

of low concentration,

down the concentration

gradient.

includes

definition

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

Key Ideas:

The movement of water molecules through a partially permeable membrane from a

solution of high water potential, to a solution of lower water potential.

definition

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

Key Ideas:

Opposites!

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

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

Key Ideas:

The movement of water molecules through a partially permeable membrane from a

solution of high water potential, to a solution of lower water potential.

definition

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

Key Ideas:

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

definition