ICT IN BIOLOGY

DIFFUSION VS

OSMOSIS

YAASHINI A/P SELVARAJAHD20091034837

NATASHA KAUR A/P MINDAR SINGHD20091034839

AMARPREET KAUR A/ GURNAM SINGH D20091034873

KRISNAVIMALA A/P KRISHUAN D20091034821

GROUP MEMBERS

WHAT???

HOW???

DIFFERENCES???

SIMILARITIES????

HOW?

WHATZ TAT???

DIFFERENCES?

Any ideas??

OSMOSIS

OSMOTIC GRADIENT

- Difference in the [ ] of 2

solution EITHER side

semi-permeable membrane

Movement of H2O

molecules- [Higher] to

[lower] region [H2O] =

GRADIENT

Movement across the

semi-permeable membrane until (=) is

reached

when H2O molecules move from hypotonic

solution to a hypertonic solution.

Pressure that applied to solution -Prevent

inward flow of H2O

DIFFUSION

spontaneous or

random movemen

t of molecules

[Higher] to [lower

] solute

Transfer of kinetic

energy(K.E) take place due to the collisions

BETWEEN MOLECULES

K.E brings about a constant motion in

between the molecules

COLLIDING EACH

OTHER

SPEED RATE

dependent on the

K.E of the molecules

COMPARISON

DIF

FE

RE

NC

ES

• Nature of transport ( no membrane required)

• Flow from [higher] to [lower] of solute

• Flow from [lower] to [higher] of solvent

• Between gas molecules, solid-liquid or liquid-gas

• Relatively faster• Can spread over long

distance

• Nature of transport (presence of a semi-permeable membrane)

• Flow from [lower] to [higher] of solute

• Flow from [higher] to [lower] of solvent

• Only between two solvents

• Relatively slower (time-dependant process)

• Is limited to short distances

DIFFUSION OSMOSIS

SIMILARITIES

Occur in living and non-living systems

do not require any

external energy to drive the process

take place along the

concentration

gradient.

Passive transport

Osmosis Concept

1. Water molecules are always moving about

2. Net movement of WATER MOLECULES (Solvent) from a solution of [higher] of water to one with [lower] of water

3. Movement of WATER MOLCULES must be through a PARTIALLY PERMEABLE MEMBRANE

WATER POTENTIAL

Instead of using the word concentration for water…

We use WATER POTENTIAL

- Water potential is the measure of tendency for water to move from one place to another

- Water moves from High Water Potential to Low Water Potential

‘High’ Water Potential

‘Low’ Water Potential

Osmosis Concept (revised)

1. Net movement of WATER MOLECULES (Solvent) from a solution of higher concentration of water to one with lower concentration of water

2. Movement of WATER MOLCULES must be through a PARITALLY PERMEABLE MEMBRANE

water potentialwater potential

Legend Water

molecule

Solute molecule

Container B (Diluted Solute Solution)

66.6% Water Concentration

33.33% Solute Concentration

Container A (Concentrated Solute Solution)

20% Water Concentration

80% Solute Concentration

Partially Permeable Membrane

Remember Diffusion? Net Movement of particles down a concentration gradient from an area of higher concentration to an area of lower concentration!

It’s about the Word Play

Concentrated Solution (Sucrose for example)

Low Water Potential

Low concentration of Solvent

High concentration of Solute

Hypertonic compared to B

Dilute Solution

High Water Potential

High Concentration of Solvent

Low Concentration of Solute

Hypotonic compared to A

A B

80% sucrose

20% water

20% sucrose

80% water

Net

MISCONCEPTIONS

Issue Naive Idea* Scientific Idea

Concentration Students often base their predictions regarding the overall direction of osmosis on the concentration of the solute (e.g., 70% sugar, 20% sugar).

The concentration of water is the factor that determines the overall direction of osmosis, and H2O concentrations are

approximately inversely proportional to solute concentrations (e.g., 30% H2O,

80% H2O).Movement Common solute molecules

such as salt and sugar will diffuse through a semipermeable

membrane.

Only water and other small, neutral molecules (such as oxygen and carbon dioxide) can diffuse across a semipermeable membrane; sugar molecules and salt ions are too large and carry too much charge.

Constraints Osmosis will continue until equilibrium is reached, with equal concentrations of solute on both sides of the semi-permeable membrane.

Osmosis often fails to reach equilibrium levels because of other factors, such as pressure inside a plant cell or atmospheric pressure on a column of water.

Rate Students often miss questions about rate of reaction, presumably because this is rarely emphasized in texts and their mental model of molecular movement is not very robust.

The higher the temperature, the faster the rate of diffusion, all other things being equal.

TO RECALL…

HERE ARE THE ACTIVITIES

Semi-Permeable Membrane

A

10% sucrose solution

B

20% sucrose solution

Solution A is hypertonic solution

Solution B is hypotonic solution

“Osmosis taking place via the uni-direction movement of water molecules from A to B”

Spot the errors!

POE

Semi-Permeable Membrane

A

10% sucrose solution

Solution A is hypertonic

Solution B is hypotonic

“Osmosis taking place via the uni-direction movement of water molecules from A to B”

Spot the errors!

V

V

A

10% sucrose solution

B

20% sucrose solution

1. Semi-permeable membrane (Partially)

2. This is a hypertonic solution (need to be relative to something)

3. Molecules only move from high water potential to low water potential (It’s the net movement, molecules do not stop moving

anyway)

Misconceptions

 

2 20 drops of vanilla

 

 

QUESTION: Will you be able to smell the vanilla that is inside the balloon? Why or why not?

PURPOSE: • Can the students apply the concept of permeability? • Do students believe that a balloon can be semi-

permeable? • Do they believe that its semi-permeability will allow

them to smell the vanilla through the balloon?

TECHNIQUE TO OVERCOME MISCONCEPTION(DEMONSTRATION)

QUESTION: If freshener is sprayed in the front of the classroom, will the students in the back be able to smell it?PURPOSE:•Do the students believe that molecules are constantly in motion? •Do students believe that molecules want to spread out? •Are students aware of the movement of molecules from a high to low concentration?

Tick ( / ) for the picture related to osmosis process and tick ( X ) for the picture related to diffusion process.

Tick ( / ) for the picture related to osmosis process

and tick ( X ) for the picture related to diffusion process

PICTURE QUIZ

ATP ENER

GY

Water

ATP energy

Ink drop in solution

Gas Molecules

Blood cell Isotonic drink

Colour gas

Liquid moleculesGrape jusFish in hypotonic

SEMI-PERMEABLE MEMBRANE

Movement of moleculesMovement of substance

Solid moleculesNo semi-permeable membrane

Perfume

Semi-permeable membrane

Syrup drink

Tonicity

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WO

RD

PU

ZZ

LE

DEFINITION

Down

2.condition achieved when molecules are evenly spread in an area3.when a solution as a greater concentration of particles4.turns color in the presence of starch5.the engulfing of large particles7.prefix that means "outside"9.the diffusion of water11.active transport will remove ___ ions, while taking in potassium ions12.channel ___ can help move things across the membrane16.organelle that helps remove excess water; ______ vacuole18.the outer boundary of the cell

Across1.type of transport that requires energy3.when a solution has a lesser concentration of particles6.type of transport that does not require energy8.prefix that means "inside"10.movement of molecules from high to low concentration13.a molecule composed of two hydrogens and one oxygen14.a solution that has an equal amount of particles15.membranes that let some things through, called selectively ______17.the maintaining of an internal balance19.word that means "cell"20.a difference in concentration creates a concentration ______

THANK YOU-KANY-