Cell Transport

•Not in the book

•Use power point and printout to study

The cell membrane - functions

• controls the movement of substances in and out of cells.

• protects the cell from its surroundings

Structure of the Cell membrane:

-consists of a phospholipid bilayer with embedded proteins.

*What is Selective Permeability?

•Property of the cell membrane

•The membrane “chooses” which substances will enter in the cell and which ones will leave the cell.

*Why is it important for the cell?

•Selective permeability will let inneeded materials such as oxygen and food molecules

•Will allow waste materials to move out

•Will prevent harmful substances, virus or bacteria to enter the cell

Concentration Gradient

• When molecules move from an area where there are more molecules to an area where there are less molecules, we say that this movement follows the concentration gradient.

• No energy is needed in this process

• The cell will need energy when the molecules go against the concentration gradient

**Concentration Gradient and Cell transport

• When molecules move from an area where there are more molecules to an area where there are less molecules, we say that this movement follows the concentration gradient.

• No energy is needed in this process

• The cell will need energy when the molecules go against the concentration gradient

There are 2 major processes that the cell uses to move materials: Passive and ActiveRead the handout and make a chart including:

1) Passive Transport – explanation of passive transport and of the different types: Diffusion, Osmosis, Facilitated Diffusion

2) Active Transport – explanation of active transport

Passive transport Active transport

No energy needed, molecules follow the concentration gradient.

There are 3 types, depending on what is moving in or out of the cell:

• Diffusion

• Facilitated Diffusion

• Osmosis

In all, the materials cross the cell membrane

Needs energy because the molecules go against concentration gradient.There is only one type:

• Active Transport

The materials cross the cell membrane

Passive Transport :• Is movement of materials through a cell membrane without the use of cell energy

• it follows the concentration gradient until equilibrium.

•Equilibrium is reached when the amount of molecules moving to the inside and to the outside of the cell is the same.

•The molecules continue moving, maitaining the equilibrium.

The 3rd square shows equilibrium

1- Diffusion

•Movement of small molecules through a cell membrane.

•Ex: carbon dioxide and oxygen

•Follow concentration gradient , until equilibrium is reached.

•The collision between molecules increase their movement and the rate of diffusion

Diffusion

Observing Diffusion: Iodine-Starch experiment

• Steps:

Pour 50 ml of water in the plastic container

Pour the iodine in the plastic container

Pour 50 ml of water inside the plastic bag and add the cornstarch

Put the bag inside the container with the solution of water and iodine.

Wait 10 min and write down your observations.

Answer the following questions:

Work in pairs - Iodine Starch Experiment:The color inside the bag changes after a whileWrite your observations about the beaker

Hint: the molecules of iodine are small and the molecules of starch are big.

When both, iodine and starch mix, a color purple is produced.

1) Think about the definition of diffusion and try to explain what happened.

2) What could you compare the plastic bag to????

What is Facilitated Diffusion?

•Larger molecules or lipophobic molecules need help when passing through the cell membrane.

•Transport proteins will open channels for the molecules to move in or out of the cell.

•It does not go against the concentration gradient.

2- What is Facilitated Diffusion?

• It is diffusion for larger molecules or lipophobic molecules

•Larger molecules need help when passing through the cell membrane.

•Transport proteins will function as carriers or will open channels for the molecules to move in or out of the cell.

• It does not go against the concentration gradient.

3- Osmosis Why is it important?

•Osmosis is the diffusion of water molecules through a selective permeable membrane .

•Cells can’t survive without water, so all cells depend on osmosis.

Osmosis in Blood Cells

What is happening

to this cell and

why?

What is happening

to this cell and why?

**What happens if you put a cell in an area where the concentration of water molecules is higher outside the cell?

**What happens if you put a cell in an area where the concentration of water is lower outside the cell?

What happens if you put a cell in an area where the concentration of water molecules is higher outside the cell?

•The cell could burst

•What happens if you put a cell in an area where the concentration of water is lower outside the cell?

•The cell will shrink

Example of Osmosis in plant cells:Which one of the plants below was watered with salt water? Why?

Example of Osmosis in plant cells:Which one of the plants below was watered with salt water? Why?

A – plant watered with regular water

B – plant watered with salt water

More salt, less water molecules outside the cell, so

water will move to the outside

Cell Transport Experiment

• In this experiment we will observe one type of cell transport. We will immerse carrots in containers with water and different amounts of salts and analyse if the circumference of the carrots changed in 24 hours

• Materials per group: distilled water, carrot, salt, popsicle stick, , spoon, 2 plastic containers, beaker, scale, string, ruler and marker.

• (COPY)HINT: In order to understand what is happening to the carrots, you need to know that the salt will not cross the cell membrane.

Cell Transport Experiment

• Each group will prepare a container. Each container will have a different amount of salt.

• Label the container 0,50,100,150 depending of the amount of salt you will put in it.Measure 200 ml of water with the beaker and put it in the container.

• Weight the salt and put the salt in the water. Mix.

• Measure the circumference of the thicker part of carrot with string and ruler. Write it down on the notebook

• Tie the string around the thicker part of the carrot

• Put the carrot in the beaker, wait 48 hours to check the results

Answer in a separate sheet of paper to turn in with the whole report. Work in groups - all students complete a report

• Formulate a hypothesis for this experiment

• What is the control in this experiment?

• What are the independent and dependent variables?

• What are the constants?

• Is this a controlled experiment? Explain

• next

Answer: (consider all measurements in the class)Measure the carrots, record in the table and answer:

1.Did the results of the experiment support your hypothesis? Why?

2. In which liquid did the carrot cells lose water? How can you tell?

3. In which kind of water did the carrot cells gain water? How can you tell?

4. What is the type of Passive Transport involved in this experiment and why?

5. Explain in details what happened to the carrot that was in the syrup. What is the substance in the syrup that affected the carrot’s circumference? What happens to the water because of this substance?

6. How can you compare what happened to the carrot in the syrup to what happened with the carrot in the water with salt?

7. What was the purpose of tying the thread on each carrot?

8. Graph the final circumference of the carrot versus the amount of salt, do not include the syrup, but include also the initial measurement (line graph)

Copy the table 8/6: Circumference of the carrots according to the liquid of immersion after 72 hours

Average of the

initial circumf.

(cm)

Final measurements

(cm)

0 g. salt

Final

measurements

(cm)

50 g. salt

Final

measurements

(cm)

100 g. salt

Final

measurements

(cm)

150 g. salt

Group 0 g 50g 100g 150g Average

Initial circ. of carrot (cm)

Syrup Initial Measurements Final measurements

Active Transport

•3 types:

Active transport

Endocytosis

Exocytosis

1- Active Transport

• movement of materials through a cell membrane using cellular energy and the help of transport proteins– against the concentration gradient.

• Ex: any molecule that needs to enter the cell against the concentration gradient will need active transport

Active Transport

•Why is it important for the cell?

•Because will allow substances to enter in the cell even though these substances are already present in the cell.

•Ex: proteins, calcium, potassium and sodium

•Endocytosis

•Exocytosis

Different processes used by the cell to obtain and eliminate materials.

The materials will not cross the membrane.

It is a type of Active Transport because the cell needs energy for it to happen

Endocytosis:

• It is for VERY large molecules that can’t pass through the membrane

**Many unicellular organisms use

endocytosis to obtain food.

Exocytosis – opposite of endocytosis

- Method to eliminate

waste

- The vesicles thatnare

created by the Golgi

Bodies are removed

from the cell by

exocytosis

Image taken with an electron microscope

2- Endocytosis

3- Exocytosis

Copy the diagram and answer:What will happen to the particles in the diagrams A and C? Assume the particles are molecules of oxygen (small molecules) and that they will follow the concentration gradient.Explain why and explain what is the type of transport involved.

Copy the diagram and answer:Imagine that the particles are big molecules, and that they will follow the concentration gradient. In which direction they will move in A and in C and what is the name of the type of transport involved?

Copy the diagram below.Explain in which direction the molecules of water will move and why.What is the type of transport involved in this movement?

Fluid in the vein – outside the cell

Copy the diagram below and answer:The molecules of salt are big molecules.Imagine that the cell below need more than 4 molecules of salt to carry on basic cellular functions, so they need to enter inside the cell.Explain if the salt will be following the concentration gradient or not.What is the type of transport involved in this movement?

Outside of the cell Inside of the cell

What is the name of the cellular transport represented below? Explain

What is the name of the cellular transport represented below? Explain

What is the name of the cellular transport represented below? Explain

inside of the cell

What is the name of the cellular transport represented below? Explain

The red dots are oxygen molecules. Explain:1) in what direction DIFFUSION will occur in each one of the cases below? 2) are the molecules following the concentration gradient?3) do they need extra energy to move?

The red dots are water molecules. Explain:1) in what direction Osmosis will occur in each one of the cases below? 2) are the molecules following the concentration gradient?3) do they need extra energy to move?