Chapter 3 Cell Processes

Chapter 3

Cell Processes

Ch. 3-2 Moving Cellular

Materials

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Structure of the Cell Membrane

Cell Membrane

The cell membrane is made of 2 layers of phospholipids called the lipid bilayer.

Close that window!!!

There are many reasons we open and shut the windows in our house.

Do you want to let all of the bugs and leaves in?

A window screen provides the protection to keep unwanted things outside, but it also allows some things to pass into and out of the room like air, unpleasant odors, or smoke.

How does the cell membrane carry out similar functions to that of a window screen?

The cell membrane

A cell membrane, like a screen, will let some things through more easily than others.

Ex: Air gets through a screen, but insects are kept out.

A cell’s membrane is “selectively permeable”. In other words it allows some things to enter or leave the cell while keeping other things outside or inside of the cell.

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SolubilityMaterials

that are soluble in lipids can pass through the cell membrane easily.

What determines how particles move in and out of the cell?

Which way particles move depends on the

a) size of the molecule or particle,

B) the path taken through the membrane,

c) whether or not energy is used.

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Small molecules move through easily.e.g. O2, CO2, H2O (oxygen, carbon dioxide, water)

Semipermeable Membrane

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Molecules larger than water, (such as proteins), do not move through the membrane on their own.

Semipermeable Membrane

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Types of Transport Across Cell Membranes

Moving things “without energy”

The movement of substances through the cell membrane “without using energy” is called passive transport.

The cell membrane can move things into and out of the cell without using energy either by:

Simple diffusionOsmosisFacilitated diffusion

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DiffusionSimple Diffusion

Doesn’t require energy Moves from high to

low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.

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Simple Diffusion In other words Molecules move

from crowded to less crowded areas of concentration.

This can occur in solids, liquids, and gases.

Diffusion “in action”…..

You might smell perfume when you sit near or walk past someone wearing it. This is because the perfume molecules are randomly moving throughout the air .

The molecules are going from an area that is crowded (such as inside the bottle) to a less crowded area (such as the air itself).

There’s more space for the molecules to spread out and move in the air.

Diffusion stops once there is an equal number of molecules in both areas.

The molecules are in equilibrium.

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DIFFUSION

Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY

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Diffusion of Liquids

Diffusion through a Membrane

Cell membrane

Solute moves DOWN concentration gradient (HIGH to LOW)

Let’s Take a Look!

Animation of How Diffusion Works

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OsmosisDiffusion of “water”

across a membraneMoves from HIGH

water potential (low solute) to LOW water potential (high solute)

Concentration = the amount of a substance in a given volume.

Diffusion across a membrane

semi-permeable membrane

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Diffusion of H2O Across A Membrane

High H2O potentialLow solute concentration

Low H2O potentialHigh solute concentration

Click on Picture for Animation

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Practice: Sample 1

CELL

10% NaCl90% H2O

20% NaCl80% H2O

What is the direction of water movement?

ENVIRONMENT

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Practice: sample 2

CELL

15% NaCl85% H2O

5% NaCl95% H2O

What is the direction of water movement?

ENVIRONMENT

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Practice 3….

CELL

10% NaCl90% H2O

10% NaCl90% H2O

What is the direction of water movement?The cell is at _______________.equilibrium

ENVIRONMENT

NO NET MOVEMENT

Practice 4

What is the direction of salt (NaCl) movement?

40% NaCl60% H2O

CELL

ENVIRONMENT

20% NaCl80% H2O

Practice 5

What is the direction of salt (NaCl) movement?

20% NaCl80% H2O

CELL

ENVIRONMENT

90% NaCl10% H2O

Wrapping it up...

1. What is the “fuel” for all cells? ________

2. Diffusion is the movement of particles from ________ areas of concentration to areas of __________ concentration.

3. Osmosis is a specialized type of diffusion that involves the movement of ___________.

Bellwork questions…..

A simple rule to remember is: salt sucksSalt is a solute. When it is concentrated inside or outside the cell, it will draw the water in its direction.

This is also why you get thirsty after eating something salty!

100% water0% salt

30% salt70% water

“Flower”

“container”

The addition of salt in the container lowers the concentration of water. The water concentration is higher in the cells of the flower.

What happens when you put salt on a snail?

They will shrivel up!!! Why? The bodies of snails and slugs contain much

water in them.  Due to the process of osmosis, in the scenario of salt and snails, the snails act as the area with high water concentration. On the other hand, the salt that you add to the snails has a low water concentration.

The snails really do not melt when we add salt.  They dry up because too much water in their bodies is sucked out of them and into the salt.  The poor snails shrivel up and die as a result.

BellworkDraw the illustration…

CELL

25% NaCl65% H2O

35% NaCl35% H2O

What is the direction of water movement?What is the direction of the salt (NaCl)?Explain your answer.

Molecules move from areas of high concentration to lower concentration

ENVIRONMENT

Into the cellOut of the cell

What do you think?

A fish that is accustomed to living in salt water is placed in fresh water. What do you predict might happen to the cells of the fish?

A. They might shrink up and cause the fish to die.B. They would become healthier because the water is so fresh.C. They might burst and cause the fish to die.

What do you think?

A fish that is accustomed to living in salt water is placed in fresh water. What do you predict might happen to the cells of the fish?

A. They might shrink up and cause the fish to die.B. They would become healthier because the water is so fresh.C. They might burst and cause the fish to die.

The process of osmosis would explain the net movement of water into a cell if the percentage of

A. water was 90% inside the cell and 95% outside the cell

B. water was 95% inside the cell and 90% outside the cell

C. protein was 30% inside the cell and 35% outside the cell

D. water and protein was equal inside and outside the cell

The process of osmosis would explain the net movement of water into a cell if the percentage of

A. water was 90% inside the cell and 95% outside the cell

B. water was 95% inside the cell and 90% outside the cell

C. protein was 30% inside the cell and 35% outside the cell

D. water and protein was equal inside and outside the cell

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Facilitated diffusion (passive

transport)Doesn’t require energyUses transport proteins to move material from high to low concentrationExamples: Glucose or amino acids (chain of proteins) moving from blood into a cell.

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Facilitated Diffusion

Molecules will randomly move through the pores of the cell membrane in protein channels.

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Facilitated DiffusionSome carrier

proteins do not extend through the membrane.

They bond and drag molecules through the lipid bilayer and release them on the opposite side.

Brainpop on “passive transport”

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passive transport

BellFUN

**Fred pours the salty water from his ice cream maker on the grass in his yard.

What will happen to the grass and why?

Finish your diffusion practice sheet so we can go over it.

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Active TransportRequires energy (or ATP)Moves materials from LOW to HIGH concentration. It goesAGAINST the concentration gradient

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Moving the “Big Stuff”Large molecules move materials into the

cell by endocytosis.

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Endocytosis

.

It takes in dissolved molecules as a vesicle. This is sometimes called “Cell drinking”.

Moving the “Big Stuff”

Large molecules are moved out of the cell by vesicles that fuse with the cell membrane through exocytosis.

Exocytosis-

moving large things out.

This is how many hormones are secreted and how nerve cells communicate with one another.

Brainpop on active transport

active transport

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Assignment: Create your own illustrations of passive

transport, active transport, endocytosis, and exocytosis. Color and label. Yes, you may use the book as a guide.

Bellwork

1. The arrows in the diagram represent the direction of movement of a certain type of molecule through the cell membrane of two different cells. The dots represent the relative concentrations of this molecule. Which processes are illustrated in the diagram?

Review Happy Science Day! Examine how the

particles in each example are moving and tell if the process is osmosis, equilibrium, simple diffusion, facilitated diffusion, or active transport.

1. 2.

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Examine how the particles in each example are moving and tell if the process is osmosis,

equilibrium, simple diffusion, facilitated diffusion, or active transport.

3. 4.

Examine how the particles in each example are moving and tell if the process is osmosis, equilibrium, simple

diffusion, facilitated diffusion, or active transport.

5.