Cell Transport

BiologyUnit 4 Notes #4

(Section 3.5)

Required for cells to allow nutrients in and get wastes out through the semi-permeable (cell) membrane

Two Main Types Passive Transport

DiffusionOsmosisFacilitated Diffusion

Active TransportEndocytosisExocytosis

Passive Transport

Passive transport: Cell spends no energy (ATP) to move molecules from high

concentrations to low concentrations (concentration gradient)

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

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

The woman inhales a breath of oxygen

The oxygen spreads into the woman’s 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!

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

A – Oxygen diffuses into your cellsB – Your heart pumps oxygen-rich blood around your bodyC – Oxygen moves into your lungsD – Oxygen gas is inhaledE – Oxygen diffuses from your lungs into your blood

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

A – Your heart pumps CO2-rich blood towards your lungsB – CO2 waste is created by every cellC – CO2 is pushed out of your lungs and out of your mouthD – CO2 diffuses from your blood into your lungsE – CO2 diffuses from your cells into your blood

Facilitated Diffusion

The molecules get help passing through the cell membrane (they are “facilitated” in their entrance)

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

Osmosis

Defined: Diffusion of water from a high to low concentration

So, water will flow through a semipermeable membrane from area of lots of water to areas of lots of solute

Distilled water(no solutes in water)

Cell(High solutes)

Cell

Osmosis

Defined: Diffusion of water from a high to low concentration

Salt water(high solutes)

Cell(low solutes)

Cell

Osmosis

Shriveled cell normal cell swollen cell

Review

1) 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) Which chemical is involved in osmosis?5) Examine the picture. If the dots are

solutes, where is the high solute concentration?

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

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

Active Transport

Defined: Molecules move from a LOW to a HIGH concentration Against the concentration gradient

ATP energy needed to fight diffusion ATP = Adenosine Triphosphate

Endocytosis

Endocytosis: Process in which the plasma membrane takes in substances Also uses carrier proteins 1) Phagocytosis: when a cell engulfs a solid

particle 2) Pinocytosis: when a cell engulfs a liquid

particle

Exocytosis

Defined: Process when substances are expelled from the cell Proteins, nutrients, and waste exit by exocytosis Packaged by Golgi body into vesicles

Vesicles carry & release objects through the plasma membrane

Active Transport

Review1) How are active and passive transport

different?2) Which molecule powers active transport?3) How are endo- and exocytosis similar?

Different?4) Which cell part controls active transport?5) The end.