Transport Across Membranes

Comparing Passive and Active Transport

Active Transport

Cells and Osmosis

Examples of Passive Transport

Passive Transport

Transport Across Membranes

Passive Transport• Passive Transport: movement of molecules

across a membrane from an area of high concentration to an area of low concentration.

• Passive Transport does not require energy.• Three types:

– Diffusion– Osmosis– Facilitated Diffusion

Examples of Passive Transport

1) Diffusion: the movement of any particle from high to low concentration.

Glue this picture beneath your definition, Label the areas of high and low concentration, then shade them two different colors.

2) Osmosis: the movement of water from high to low concentration.

Glue this picture beneath your definition, Label the areas of high and low concentration in each picture, then shade them two different colors.

Examples of Passive Transport

3) Facilitated Diffusion: movement of large molecules from high to low through transport proteins.

Glue this picture beneath your definition, Label and shade the areas of high and low concentration, and the transport (carrier) proteins.

Examples of Passive Transport

Cells and Osmosis

Hypotonic—water moves into the cell High Low. Therefore cell swells.

Isotonic—water moves in and out of cell because there is no concentration difference. Therefore cell does not change.

Hypertonic—water moves out of cell High Low. Therefore cell shrivels.

Cells and Osmosis• In animal cells, hypotonic conditions can

lead to lysis, cells bursting.• In plant cells, hypotonic conditions provide

the water pressure needed to support the cell wall.

• In plant and animal cells, hypertonic conditions cause cells to shrivel (this is why plants wilt when not watered).

Active Transport• Active transport: movement of molecules from

an area of low concentration to an area of high concentration.

• Active transport uses membrane proteins that require energy (ATP).

Glue down the picture, then label and shade:- Areas of high & low concentration- Membrane proteins- ATP

Active Transport• Endocytosis: uses lots of energy to move

particles inside the cell. • Exocytosis: uses lots of energy to move

particles outside the cell.Endocytosis

Exocytosis

Uses energy

No energy required

Osmosis DiffusionSemi-

permeable membrane

With a gradient High Low Low High Movement

of particlesFacilitated diffusion

Exocytosis Membrane protein

Against a gradient

Endocytosis ATP

Comparing Active & Passive Transport

• In the top portion of the flap, draw a Venn diagram. Label one circle Active Transport and the other Passive Transport.

• Place the words from the chart below into the appropriate places on the Venn diagram.

Comparing Active & Passive Transport

High

Low

Active Transport

Low to High

Uses Energy

Passive Transport

High to Low

No Energy