What are the four parts of a cell that EVERY cell

has? (Look waaay back to cell theory)

A. Plasma membranes form a boundary between

the inside and the outside environment

1. It is made by a two-layer structure called the

phospholipid bilayer

2. A phospholipid has 2 basic parts:

a. A head that “loves” water (hydrophilic)

b. A tail that “hates” water (hydrophobic)

3. The “head” is a polar molecule (attracted to water

molecules), the “tail” is non-polar (avoids water)

4. Membranes have “heads” on outside and “tails” on

inside so only the heads interact with water

The cell membrane is “semi-permeable”,

which means that it regulates the passage

of materials into and out of the cell

5. Other molecules are embedded within the membrane

a. Proteins form channels through membrane for transportation

b. Cholesterol molecules strengthen cell membrane

c. Carbohydrates attached to proteins act like “identification tags”

On a blank page

Draw a Cell membrane that spans horizontally

across the center of one page,

In this membrane Label the parts of the

phospholipid bilayer (Including charges)

Include An example of each molecule shown

above

Draw 5 water molecules on each side of the

membrane

We will be using this diagram for Cell transport

What are the major parts of a cell membrane?

What does selectively permeable mean?

Cells maintain a balance between

themselves and their environment

This balance is called equilibrium

Molecules are in constant motion.

As they move, they tend to go to areas that are

less crowded or “concentrated”.

Molecules always move from an area of high

concentration to an area of low concentration

Diffusion.swf

Two examples of diffusion & passive

transport (no energy required)

1. Perfume / scent around a room

2. Food coloring in water

Small Uncharged molecules, O2 CO2

Can move directly through Lipid bilayer

In diffusion and osmosis, the molecules move

“downhill” or with the concentration gradient.

Notice how no energy is required to move in

passive transport

High Concentration

Low Concentration

Isotonic Environment

The concentration of molecules is equal inside

and outside of the cell

Water enters and leaves equally

Hypotonic Environment

The concentration of molecules is lower outside of the

cell

More water enters than leaves

“hypo-” means “below” or “under”

What are some other words that start with “hypo-”?

Hypodermic, hypothermia, hypoallergenic, hypoxia,

hypoglycemic

Hypertonic Environment

The concentration of molecules is higher outside of the

cell

More water leaves than enters

“hyper-” means “above” or “higher”

What are some other words that start with “hyper-”?

Hyperactive, hyperextend, hypertension, hyperbaric, hyperbole,

hyperglycemic, hypersensitive, hypersonic, hyperventilate

Hypotonic?

Hypertonic?

Isotonic?

In facilitated diffusion, molecules are too big to

fit through the membrane directly

The molecules will instead pass through special

protein “channels” or “carrier proteins” in the

cell just for these molecules

Like diffusion, it does not require energy

Carrier Protein.swf

Water actually has a difficult time crossing the cell

membrane

Instead, it uses facilitated diffusion to cross the

membrane through protein channels called

“aquaporins”

Aquaporin.mpg

• When molecules move across a cell membrane

it is called diffusion

• When water moves across a cell membrane, it is

called osmosis

Osmosis.swf

Purpose to observe how salt water affects the

structure of a plant cell through the loss of water

due to osmosis

Hypothesize: What will happen to the Elodea

cells when they are exposed to salt water?

Procedure Grab a leaf of elodea out of the beaker, Make a

wet mount slide with H2O and observe at all

objectives

Draw the FOV for the 400x total magnification

and Label the Cell wall, Vacuole and

Chloroplasts in your Notebook

Clean your slide and prepare another wet mount

slide this time using Salt water, wait 10

minutes then Observe at all objectives and

Draw at 400x magnification.

Describe the differences you see between the

fresh water mount and the salt water mount.

Explain how the process of osmosis can be

attributed to the differences you see.

Why didn’t the cell wall keep the cell from

changing it’s water content?

Want to keep cookies fresh longer?

Describe the three cellular environments

What type of environment are these cells

exposed to?

Sometimes molecules

the cell needs are too

big to diffuse into or out

of the cell

The cell must use

energy to move these

molecules into or out of

the cell

When the cell must use

energy, it is called

active transport

High Concentration

Low Concentration

Active Transport moves molecules from an area of

LOW concentration to an area of HIGH

concentration

In other words, they are moving AGAINST the

concentration gradient

Notice how energy is required in active transport

• There are 4 types of active transport, all of which require energy

1. Endocytosis– Cell brings in material

2. Pinocytosis– Cell “drinking”

3. Phagocytosis– Cell “eating”

4. Exocytosis– Cell releases waste

• Each of these involves bringing materials into the cell except for exocytosis.

In molecular transport, small

molecules are carried or

“pumped” across the cell

membrane

In bulk transport, large

molecules or even solid

clumps of material can be

moved across the membrane

Phagocytosis.swf Active Transport & Facilitated Diffusion.swf