DIFFUSION AND OSMOSIS

Types of Cellular Transport

Passive Transport cell doesn’t use energy

1. Diffusion2. Facilitated Diffusion3. Osmosis

Active Transportcell does use energy

1. Protein Pumps2. Endocytosis3. Exocytosis

high

low

This is gonna

be hard work!!

high

low

Weeee!!!

Bacon Frying…

What do you smell?

Why do you smell this?

Bacon Frying…

• Fat droplets are released into the airsteam coming off of the bacon

• Causes the fat droplets (particles) to collide and disperse.

In science terms…• DIFFUSION IS OCCURING!

• The bacon fat droplets (particles) diffuse from the area of high concentration (directly above the frying pan), to areas of low concentration (the room)

• Continues until equilibrium is reached Particles equally distributed

throughout the space (room)

Diffusion

Diffusion - Defined as the movement of particles from areas of high concentration to areas of low concentration (down the concentration gradient) Particles spread out Ex: Solute = perfume Solvent = the air

Low Solute Concentration

High Solute Concentration

Diffusion

Diffusion rate (how fast it occurs) depends on:

1. Size- smaller molecules move more easily

2. Concentration- high concentration = faster spread

Ex: The more bacon you have (=more fat droplets released), the faster the smell will spread throughout the room

3. Temperature- high temps speed up the process

Which will cause the smell to disperse faster? Cold bacon in a frying pan and the stove is OFF

OR Bacon in a frying pan and the stove in ON

What is a semi-permeable membrane?

A membrane that allows certain molecules to pass through it by diffusion or osmosis

Think about a Ping-Pong net..

Which would pass through?

Osmosis

Diffusion that involves waterwater. Movement of water across a semi-

permeable membrane

Cell membranes are semi-permeable Water and some gases move through the

membrane easily, while larger molecules like proteins and sugars do not.

Cells must regulate- molecules move from internal environment to external environment (and vice versa) so that both environments have equal concentrations. Animation: How Osmosis Works

Osmosis

Diffusion that involves waterwater. Movement of water across a semi-

permeable membrane Water moves from areas of low

solute to areas of high solute

Why do your fingers “shrivel–up” when you are in the water?

Effects of Osmosis on Life

Osmosis- diffusion of water through a selectively permeable membrane.

There are 3 types of solutions (=Tonicity) 1.) Isotonic2.) Hypertonic3.) Hypotonic

Isotonic Solution

Solutions that contain the same concentration of solutes as the cytoplasm are called isotonic (or normal saline) solutions.

There is no net movement of water either into or out of the cell.

Cells maintain their normal shape.

WATCH VIDEO OF BLOOD IN AN ISOTONIC SOLUTION

Isotonic Solution

Isotonic Isotonic The concentration of solutes in the external solution is equal to the concentration of solutes inside the cell.

Result Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

• Osmosis Animations for

isotonic, hypertonic, and

hypotonic solutions

Hypertonic Solution

A hypertonic solution is a solution that contains more solutes than the cytoplasm of the cell. (hyper)

Has less water than the cell and water moves out of the cell. The cells shrink.

WATCH VIDEO OF NORMAL RBCs SUBJECTED TO A HYPERTONIC SOLUTION

Hypertonic Solution

Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)

Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis/crenation)!

• Osmosis Animations for

isotonic, hypertonic, and

hypotonic solutions

shrinks

Hypotonic Solution

A hypotonic solution contains less solute (thus, more water) than the cytoplasm of the cells.

The water will move into the cells resulting in the swelling and lysis of the cells. 

WATCH VIDEO OF CRENATED RBCs SUBJECTED TO A HYPOTONIC SOLUTION

Hypotonic Solution

Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)

Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

• Osmosis Animations for

isotonic, hypertonic, and

hypotonic solutions

Let’s take a closer look!

http://www.coolschool.ca/lor/BI12/unit4/U04L06/rbc.html

What type of solution are these cells in?

A CB

Hypertonic Isotonic Hypotonic

Tonicity

Used to compare different solutions Hypertonic- higher solute concentration

relative to another*think hyperactive

Hypotonic- lower solute concentration relative to another

*think hypothermia

Isotonic- equal solute concentrations between two solutions

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Cell in Isotonic SolutionCell in Isotonic Solution

CELLCELL

10% NaCL90% H2O

10% NaCL

90% H2O

What is the direction of water movement?

The cell is at _______________.equilibrium

ENVIRONMENTENVIRONMENT

NO NET NO NET MOVEMENTMOVEMENT

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Cell in Hypotonic Cell in Hypotonic SolutionSolution

CELLCELL

10% NaCL90% H2O

20% NaCL

80% H2O

What is the direction of water movement??

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Cell in Hypertonic Cell in Hypertonic SolutionSolution

CELLCELL

15% NaCL85% H2O

5% NaCL95% H2O

What is the direction of water movement?

ENVIRONMENTENVIRONMENT

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Cells in SolutionsCells in Solutions

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Isotonic Solution

NO NET MOVEMENT OF

H2O (equal amounts entering

& leaving)

Hypotonic Solution

CYTOLYSIS

Hypertonic Solution

PLASMOLYSIS

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Cytolysis & PlasmolysisCytolysis & Plasmolysis

Cytolysis Plasmolysis

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Osmosis in Red Blood Osmosis in Red Blood CellsCells

Isotonic Hypotonic

Hypertonic

What Happens to Blood Cells?

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