With your table partner answer these questions:

1. In order for a cell to survive, what substances might need to

get into a cell or out of a cell?

2. What structure do things need to get past in order to get in or

out of cells?

3. Would it be easier for you to get to a place by walking with

the wind or against the wind? Up hill or down hill?

In order to understand the transport of materials in

and out of the cell we will focus on the barrier

between a cell and its environment. Do you know

what that barrier is?

• Why yes of course, it is the cell membrane!

First let’s take a closer look at a

soap bubble, why?

Note how the surface is not static.

It swirls and moves freely.

Or consider the molecules in the

membrane sort of like a ball pit.

They can move around.

THINGS NEED TO PASS THROUGH THE

Cell Membrane The cell membrane is made up a __________________________.

Phospholipids have a head that is attracted to water

_____________________ and a tail that repels water ___________.

DOUBLE LIPID LAYER

HYDROPHILIC HYDROPHOBIC

In the cell, there are 2 layers of phospholipids. As you can see

in the drawing below, the 2 layers of lipids have the “heads”

facing outward toward the water, and the “tails’ facing inward

where there is no water. This double layer of phospholipids

forms a tough yet flexible _________________. MEMBRANE

Also located within the lipid bilayer are ____________________

and ____________________ chains..

Protein channels

carbohydrates

The proteins

can act as

channels or

pumps.

They also

identify your

cells and

sometimes act

as receptor sites.

The carb

chains

identify the

cell as

belonging to

you. They

are like little

labeling

flags. If a cell enters your and has different

carbohydrate chains, the white blood

cells will attack them because they

are foreign invaders of your body.

So how does stuff move in and

out of a cell?

• In some cases it moves very easily by

following a concentration gradient.

• What the heck is that?

A situation in which particles are highly concentrated in one area

and in low concentration elsewhere.

PASSIVE TRANSPORT: Movement of small particles across a

membrane WITHOUT USING ENERGY!

DIFFUSION

Random movement

of particles from

areas of high to low

concentration

OSMOSIS

THINK “H2O-

smosis”

Movement of water

from high to low

concentration

FACILITATED

DIFFUSION

Allows larger

particles to get

through by using

protein channels

THE KEYS THINGS ABOUT PASSIVE TRANSPORT ARE

1- THEY DO NOT REQUIRE ENERGY

and

2- THE THREE TYPES ARE: diffusion, osmosis, and facilitated

diffusion.

OSMOSIS

DIFFUSION OF WATER.

What makes this type of diffusion have a special name?

•It is for WATER

• Diffusion is general, osmosis is specific

•Water must cross a membrane

In organisms, osmosis transports

water INTO or OUT OF cells.

This stuff is so fascinating, let’s

watch a cool movie on it.

KEY POINT TO REMEMBER:

IN OSMOSIS, WATER WILL

ALWAYS ALWAYS ALWAYS MOVE

FROM AN AREA WHERE IT IS

HIGHLY CONCENTRATED TO AN

AREA OF LOW CONCENTRATION.

WHAT TYPE OF CELLS HAVE CELLS WALLS?

If there is a lot of water entering a plant’s cells by osmosis, it has a

lot of water pressure pushing out on the cell walls. This type of

water pressure is called

EXAMPLES OF HIGH

AND LOW TURGOR

PRESSURE:

Notice the cell wall and

the cell membrane.

The environment in which a cell resides

The solution in which the cell is exposed to (its

environment) will either make it shrink, swell, or stay

the same. There are 3 types of solutions it can be in:

hypotonic, hypertonic, and isotonic.

HYPO means…

HYPER means…

ISO means…

Below; beneath; under

Less than normal; deficient

Over; above; beyond

Excessive; excessively

Equal

LAB TIME

Let’s explore some cells in different environments.

HYPOTONIC

•Water moves into cell from solution

•Cell expands (and may burst) = CYTOLYSIS

Solutions that have a LOWER amount of water inside the

cell than outside the cell.

.

MORE HYPOTONIC

SOLUTIONS

CYTOLYSIS: The swelling of a cell due to water moving into the

cell.

HYPERTONIC SOLUTIONS Solutions that have a HIGHER amount of water inside the

cell than outside the cell.

•Water moves out of the cell into the solution

•Cell shrinks - plasmolysis

MORE HYPERTONIC

SOLUTIONS

PLASMOLYSIS: The water loss due to water moving out of the

cell to a lower concentration. Cell will shrink.

ISOTONIC SOLUTION Solutions that have an equal amount of water inside the

cell and outside the cell.

EQUILIBRIUM: Equal amounts of water move in and out of cell.

Facilitated Diffusion

Only very very very small particles can get

through a cell membrane by diffusion. A cell has

another way of getting bigger ones inside.

Facilitated diffusion allows larger particles to

enter the membrane by diffusion. There are

_____________ _______________ within the cell

membrane that act as tunnels that let them in.

When a particle gets inside the cell through these

channels, it is called facilitated (helped) diffusion.

PROTEIN CHANNELS

PASSIVE TRANSPORT IN ACTION: Facilitated diffusion for

bigger particles

Molecules will randomly move through the opening in a process

called diffusion. This requires no energy, molecules move from an

area of high concentration to an area of low concentration.

REQUIRES NO ENERGY

Processes where something gets into

or out of the cell by a procedure which

uses ENERGY!

There are 3 types of active transport:

PUMPS If a particle needs to get into or out of the cell against the

concentration gradient, it will need to use ENEGY. This means

that the particles need to go from an area of LOW concentration to

an area of HIGH concentration.

THEY ARE MOVING AGAINST THE CONCENTRATION

GRADIENT!

Within the cell membrane are PROTEINS that have channels

which act as pumps.

Let’s take a look at a pump in action

PUMPS in action

Some proteins actively use energy from the ATPs in the cell to drag

molecules from area of low concentration to areas of high concentration

(working directly against diffusion) an example of this is the

sodium/potassium pump. Here the energy of a phosphate (shown in red)

is used to exchange sodium atoms for potassium atoms.

Large Particle Movement

Sometimes larger things need to enter or exit

the cell, but they cannot fit through a

protein channel. They will enter or exit by

endocytosis or exocytosis.

ENDOCYTOSIS: Cell surround an object and engulfs it within

the membrane and forms a vacuole.

The cell membrane can also engulf structures that are much too

large to fit through the pores in the membrane proteins this process

is known as endocytosis. In this process the membrane itself wraps

around the particle and pinches off a vesicle inside the cell. In this

animation an ameba engulfs a food particle.

EXOCYTOSIS The cell pushes a vacuole to its surface, the

vacuole opens and the object is expelled.

Large molecules that are manufactured in the cell are released through

the cell membrane.

EXAMPLES of ENDO:

EXAMPLES of EXO:

•Exocytosis (animation) click for movie link

White blood cells

Amoeba engulfing paramecium

Cells expelling waste

THE END