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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
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
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