Passive Transport

Passive Transport• Passive transport: Cell spends no energy (ATP) to move

molecules

Does this kayaker need to spend his energy in order to move?

Passive Transport• Passive transport: Cell expends no energy (ATP) to move

the molecules• Molecules move from a high to low concentration

– Down their concentration gradient

• Examples:o Diffusiono Osmosiso Facilitated diffusion

• Diffusion: Movement of molecules from an area of high to low concentration

• Movement continues until equilibrium is reached– Equilibrium: even balance of molecules

• This is how many molecules move into and out of cells

O2

O2

O2O2

O2

O2

O2

O2

O2

O2

O2

O2O2

O2

O2

O2O2

O2

O2

O2

O2

O2

Will oxygen mostly enter or exit this cell?

• Diffusion: Movement of molecules from an area of high to low concentration

• Movement continues until equilibrium is reached– Equilibrium: even balance of molecules

• This is how many molecules move into and out of cells

Diffusion Video Clip

The woman inhales a breath of oxygen

The oxygen spreads into the womans lungs

The oxygen fills the air sacs (alveoli) located in her lungs

Where is the HIGH oxygen concentration?

Where is the LOW oxygen concentration?

Due to diffusion, the oxygen will spread from her lungs… into her blood

The heart pumps this oxygen-rich blood around her body

Cell X needs oxygen just like all cells. But cell X is not in direct contact with the blood and oxygen. So how does cell X get oxygen?

Where is the HIGH oxygen concentration?

Cell X (and all other cells) gets oxygen through the process of diffusion!

Diffusion: movement of molecules from a high to low concentration

Where is the LOW oxygen concentration?

The reverse process is true w/ carbon dioxide. Over time, CO2 waste builds up in cells. Too much is fatal. It must be removed.

Where is the HIGH carbon dioxide concentration?

CO2 diffuses from the cells (high concentration) and into the blood stream (low concentration)

Where is the LOW carbon dioxide concentration?

The heart pumps the CO2 rich blood back to the lungs.

Where is the HIGH carbon dioxide concentration?

CO2 diffuses into the air sacs (alveoli)

The woman begins to exhale

The diaphragm muscle pushes the CO2 out of the lungs

CO2 is expelled… the process repeats with every breath!

Osmosis• Defined: Diffusion of

water from a high to low concentration

• High H2O concentration– Less solutes

(hypotonic solution)– Ex: Distilled water

Distilled water(no solutes in water)

Cell(High solutes)

Cell

Osmosis• Defined: Diffusion of

water from a high to low concentration

• High H2O concentration– Less solutes

(hypotonic solution)– Ex: Distilled water

• Low H2O concentration– More solutes

(hypertonic solution)– Ex: Salt water

Salt water(high solutes)

Cell(low solutes)

Cell

Isotonic- when the concentration ofsolutes is the same inside and outsidethe cell.

Many cells contain water channel proteins called aquaporins

Facilitated Diffusion

• Facilitate means “to help”• Defined: Larger molecules enter/exit with the help

of protein channels in the plasma membrane• No energy (ATP) used

Protein channel

glucose

glucose

Facilitated Diffusion

Review1) In which direction does diffusion occur?

2) Across which part of the cell does diffusion mostly occur?

3) Which molecule of energy is not required during passive transport?

4) True or False: More solutes creates less concentrated water.

5) Which chemical is involved in osmosis?

6) Examine the picture. If the dots are solutes, where is the high solute concentration?

7) Examine the picture. If the dots are water molecules, where is the low water concentration?

8) Examine the picture. If the dots are water molecules, which way will osmosis occur?

9) Examine the picture. If the dots are solute molecules, which way will osmosis occur?

Review10) Place the steps of oxygen flow in the correct order from start to finish.

A – Oxygen diffuses into your cells

B – Your heart pumps oxygen-rich blood around your body

C – Oxygen moves into your lungs

D – Oxygen gas is inhaled

E – Oxygen diffuses from your lungs into your blood

11) Place the steps of CO2 flow in the correct order from start to finish.

A – Your heart pumps CO2-rich blood towards your lungs

B – CO2 waste is created by every cell

C – CO2 is pushed out of your lungs and out of your mouth

D – CO2 diffuses from your blood into your lungs

E – CO2 diffuses from your cells into your blood