Cell Transport

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(High to Low)

Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out.

http://bio.winona.edu/berg/Free.htm

Simple Diffusion Animation

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2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane

Transport Proteins are specific – they “select” only certain molecules to cross the membrane

Transports larger or charged molecules

Facilitated diffusion (Channel Protein)

Diffusion (Lipid Bilayer)

Passive Transport: 2. Facilitated Diffusion

Carrier Protein

A

B

http://bio.winona.edu/berg/Free.htm

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High Concentration

Low Concentration

Cell Membrane

Glucose

molecules

Protein

channel

Passive Transport: 2. Facilitated Diffusion

Go to Section:

Transport Protein

Through a 

Cellular Transport From a-

High

Low

Channel Proteins animations

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3.Osmosis: diffusion of water through a selectively permeable membrane

Water moves from high to low concentrations

Water moves freely through pores.

Solute (green) to large to move across.

Osmosis animation

Passive Transport: 3. Osmosis

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Active Transport

cell uses energy

actively moves molecules to where they are needed

Movement from an area of low concentration to an area of high concentration

(Low  High)

Three Types:

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Types of Active Transport

1. Protein Pumps -transport proteins that require energy to do work

Example: Sodium / Potassium Pumps are important in nerve responses.

Sodium Potassium Pumps (Active Transport using proteins)

Protein changes shape to move molecules: this requires energy!

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Types of Active Transport

2. Endocytosis: taking bulky material into a cell

Uses energy

Cell membrane in-folds around food particle

“cell eating”

forms food vacuole & digests food

This is how white blood cells eat bacteria!

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Types of Active Transport

3. Exocytosis: Forces material out of cell in bulk

membrane surrounding the material fuses with cell membrane

Cell changes shape – requires energy

EX: Hormones or wastes released from cell

Endocytosis & Exocytosis animations