2.2 Active Transport

Recap

Active Transport

Requires carrier proteins

Solute moves across a membrane

against its concentration gradient

(low high)

Requires energy

(adenosine triphosphate - ATP)

Active Transport

Primary active transport direct use of ATP

Secondary active transport indirect use of ATP

Primary Active Transport

Direct use of ATP

Carrier proteins act as ion pumps

Example: Sodium-potassium pump in a nerve cell

Sodium-

potassium

ion pump

Secondary Active Transport

Indirect use of ATP

Ion pump moves ions against its concentration gradient

charge builds up on one side

concentration gradient + electric potential

Creates an electrochemical gradient

Drives the transport of molecules or ions

Hydrogen-sucrose pump

Membrane-Assisted Transport

For large macromolecules

Requires energy

A cell forms vesicles to surround incoming or outgoing material

2 forms:

I. Endocytosis – moves materials into the cell

II. Exocytosis – moves materials out of the cell

I. Endocytosis

Cell membrane folds in and pinches off to form a vesicle

3 types:

1. Phagocytosis

2. Pinocytosis

3. Receptor-mediated endocytosis

1. Phagocytosis

aka cell-eating

Cell takes in discrete particles (eg. Organism,

fragment of organic matter)

2. Pinocytosis

aka cell-drinking

Cell takes in a liquid and the small particles

dissolved or suspended in it

3. Receptor-mediated endocytosis

Receptor proteins in cell membrane bind to specific molecules outside the cell

Cell membrane folds in to create vesicle coated with clathrin

II. Exocytosis

For large molecules or waste to leave a cell

Vesicles then become part of the cell membrane

Function:

Plant cell - to construct cell wall

Animal cell – to secrete hormones, neurotransmitters and digestive enzymes

Cell Transport

Passive Transport Active Transport

Diffusion Osmosis Facilitated

Diffusion

Channel

Proteins

Endocytosis/

Exocytosis

Carrier

Proteins

Primary Secondary

Cellular Transport: A Summary