Cellular Transport

Energy-less Transport

1) Diffusion – movement of substances from a higher concentration to lower concentration– The unequal distribution of particles is called

a concentration gradient– GOAL: EQUAL CONCENTRATION ON BOTH

SIDES– Osmosis: movement of water

Types of SolutionsInside Cell Outside Cell Movement

Isotonic Solution Concentration inside and outside of the cell is equal

Movement of material inside and outside of the cell is equal

Hypotonic Solution

More dissolved substances in the cell

More water outside the cell

Movement of water inside the cell (cell swells)

Hypertonic Solution

More water inside the cell

More dissolved substances outside the cell

Movement of water outside of the cell (cell shrinks)

Hypertonic Solution

Hypotonic Solution

Isotonic Solution

Energy-less Transport Con’t.

2) Passive Transport – movement of particles across the cell membrane

a) Proteins – special proteins (transport proteins) help larger substances move through the membrane

- Channel Proteins – aqueous channel that allows soluble material to pass into and out

of the cell - called facilitated diffusion - driven by the concentration gradient - transport sugars and amino acids

Active and Passive Transport

Active Transport

• Requires energy

• Materials move against a concentration gradient

• Acts against diffusion

• Includes use of transport proteins

• Includes exocytosis and endocytosis

How does active transport work?

1. A carrier protein binds with a particle of the substance to be carried across the membrane

1. Moves the substance across based on charge and concentration (electrochemical gradient)

2. When bonding has occurred, the chemical energy changes the shape of the carrier protein so that the particle is released into the cell

3. Once released, the carrier protein regains its original shape

Active Transport

Gated Channels

• Involved in active transport

• Form a “gate” over certain pores.

• They are stimulated to open by a “ligand”, allowing substances to pass through.

Endo- and Exo- cytosis

• Endo – in• Cell surrounds and

takes in material from the environment

• Creates a vacuole– Vacuole is called a

coated vesicle

• Exo – out• Expulsion or excretion

of wastes, secretion of hormones

Endocytosis

Exocytosis