Active Transport

pp. 67 to 71

• We know that passive transport involves NO energy, but....

• As living beings, we NEED energy to sustain life processes. We eat food containing nutrients for energy, glucose being one of them. – Recall: glucose cannot be sustained inside body as it is

soluble, so it must be converted into glycogen to get energy “stores”

– This conversion MAKES energy in the form of adenosine triphosphate (ATP) = source of energy for cells

– ATP reacts with certain compounds to release energy to drive life processes

Active Transport – 3 Types

ActiveTransport

ActiveTransport

CellMembrane

CarrierProtein

CellMembrane

CarrierProtein

EndocytosisEndocytosis ExocytosisExocytosis

1. CM Carrier Protein

• Bit similar to facilitated diffusion, but… • Cell energy (ATP) is used to move substance

across CM against concentration gradient (low high)– Remember, simple diffusion is the movement of

substances using no energy to maintain equal concentrations on both sides (high low = equal)

1. Substance (eg. protein, vitamin, molecule) binds to carrier protein.

2. Carrier protein uses energy (ATP) to flip over & “pumps” (releases) substance to other side of the membrane.

3. Carrier protein flips back to get another substance. LOW CONCENTRATION

HIGH CONCENTRATION

DIFFUSION

Bulk Transport

• Diffusion and CM carrier proteins move small amounts of molecules, sometimes ONE molecule at a time. It works but may not be the most efficient.

• Cells need to move large amounts of materials (bulk) in or out of the cell, all at once = bulk transport

• Involves energy (ATP)• Two kinds of bulk transport: endocytosis and

exocytosis

2. Endocytosis

• A type of bulk transport that is used to bring large amounts of material INTO the cell.

• There are 2 kinds:– Phagocytotis: bulk transport of solids– Pinocytosis: bulk transport of liquids

Phagocytosis: (cell eating)• large particles, whole cells

or solids enter the cell • Pseudopods (sin:

pseudopodium) enclose food

• enter as a food vacuole

Pinocytosis: (cell drinking)• bulk transport of

dissolved solutes or fluids into the cell

• enter as a vesicle

Exocytosis• A type of bulk transport that is move large

amounts of material OUT of the cell.• Materials are encased in secretory vesicles (in

case of proteins, vesicles form at the end of the Golgi appartus and breaks off)

• The vesicle move towards CM. Vesicle fuses with CM and expels content to extracellular fluids.