Diffusion

Movement of Substances

Imagine that you are in this situation. Your

mother broke a glass of perfume and you, who is studying in the same room, gradually begin

to smell the scent of the perfume…

Diffusion

• Definition: The net movement of solute particles from a region of higher concentration to a region of lower concentration, ie, down a concentration gradient.

• SI unit – mol

• Other unit – mass per unit volume

In pictorial form…

Example of Diffusion

1. Drop a piece of copper sulphate crystal into a gas jar full of water.

2. Cover the jar and allow it to stand still for a few days.

Factors involving rate of diffusion

• Concentration gradient– Steeper gradient faster rate of diffusion

• Temperature– Higher temperature faster rate of diffusion

• Size of particle– Smaller particles faster rate of diffusion

Factors involving rate of diffusion

• Rate of mixing–Faster rate of mixing faster

rate of diffusion

Question 4

Question 3

Question 2

Question 1

Quiz Time!

Diffusion occurs when particles move from a region of ___ concentration to a region of ___ concentration.

A) Higher ; Lower C) Homogenous ; Heterogeneous

B) Lower ; Higher D) Heterogeneous ; Homogenous

Question 4

Question 3

Question 2

Question 1

Quiz Time!

What is a factor involving the rate of diffusion?

A) Size of particles C) The gradient function of a curve

B) The charge of the particle D) Cuticle layer present on the epidermis

Question 4

Question 3

Question 2

Question 1

Quiz Time!

Diffusion will occur until a ___ is achieved

A) Dynamic equilibrium C) Partially permeable membrane

B) Heterogonous solution D) Charged particle

Question 4

Question 3

Question 2

Question 1

Quiz Time!

The difference in concentration between two regions is known as the ___.

A) Concentration gradient C) Gradient function

B) rise/run D) dy/dx

You are wrong.

Return to quiz

Congratulations. You have completed the course on

diffusion!

Osmosis

Movement of Substances

Osmosis

• Definition: The net movement of solvent particles from a region of higher solvent/water potential to a region of lower solvent/water potential through a partially permeable membrane

• Water Potential: Tendency of water to move down a concentration gradient and is measured in Pascals (Pa).

Hypertonic, Isotonic and Hypotonic

Osmosis

Hypertonic, Isotonic and Hypotonic

• These terms can only be applied to animal cells

• Hypertonic = water potential greater than solute concentration (eg. Distilled water)

• Isotonic = water potential equal to solute concentration

• Hypertonic = water potential lesser than solute concentration (eg. Honey)

Effect of animal cell in hypotonic solution

Effect of animal cell in hypertonic solution

• As the cell is placed in a solution hypertonic to its contents, water particles will leave it’s cytoplasm, pass the cell membrane due to osmosis.

• The cell shrinks and little spikes appear on the cell surface membrane

• This is known as crenation

Effect of animal cell in hypertonic solution

Spikes (caused by microfilaments in the cell)

In a nutshell

Effect of plant cells in solution with higher water potential

Effect of plant cells in solution with higher water potential

• The cell wall is strong relatively inelastic. It prevents overexpansion of the cell by exerting an opposing pressure as water enters the cell. This prevents more water from entering the cell.

• When a plant cell expands, it becomes swollen or turgid. The turgidity of the cell with water is known as turgor.

Effect of plant cells in solution with lower water potential

Police investigators were called to the scene and after months of trying, they found john... Dead...

The question is, how did he die?

What is your conclusion?

• He was placed in a hypertonic solution

• He was placed in a hypotonic solution

• He died from drowning

• His hat suffocated him

You are wrong

• Head back to try again

Suspects

• You start to line up the suspects. They are…– Mr I. M. Bottle– Mr U. R. ? (Last name unknown… People

speculate that his last name is concentrated. Of course, another group of people think that his last name is mad.)

– Mr T. M. R.

DM-3

DM-3

DM-3

Suspects

• Who can you safely eliminate from this list of suspects– I. M. Bottle– U. R. ?.– T. M. R. (Suspect says: I AM VOLDEMORT!!!)

Enter the LAIR!

• After many hours of investigation, you have found out that the killer was Mr. U. R. ?.

• A team of policemen rushed to arrest him… however…

Fools! You cannot enter my secret lair. It is encoded with 2 layers of passwords... And only I know what they are! And I’m not telling!

Oh FINE! The first password is the unit water potential is measure in, and the second is the pressure exerted on the cell wall when a plant is placed in a hypotonic solution

Enter the LAIR!

• The answer is obviously simple. What is it?

– Pascals ; Turgid

– Pascals ; Turgor

– Kilograms ; Flacid

– Kilograms ; Turgor

Meet… the battle droids

• Just when you thought you could finally arrest him… who would come but battle droids!

Meet… the battle droids

• Now what? The only way to defeat them is to yell the deactivation command.

• But what is this command?• You think that it is the

process where the vacuole of the plant cell shrinks and the cytoplasm pulls away from the cell wall… the only problem is… what is it?

Meet…the battle droids

• Plasmolysis• Crenation• Swellation• Turgor