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Biology 2121 Independent Notes – Cell Transport
I. Passive vs. Active Transport
(1). Some things to remember:
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Passive transport
o No energy required
o Movement from high to lower concentration areas
o Examples include simple diffusion; osmosis and facilitated diffusion
o Facilitated diffusion requires a protein carrier or channel
Active transport
o Energy in the form of ATP is required
o Movement from low to high areas of concentration
o Examples are:
 1. Primary active transport
 Phosphorylation occurs (from ATP hydrolysis)- to transport protein allowing it
to change shape
 Na+K+ pump is an example (page 76)
 2. Secondary active transport
 Single ATP pump or primary pump can drive this type of active transport
 As sodium is moved across its concentration gradient, energy is stored in the
ion gradient
 As Na flows back across, energy released allowing for the movement of other
particles
 For example on page 77 glucose is dragged along with sodium
Vesicular Transport
o Movement of very large particles, macromolecules and large amounts of fluid
o Substances move via vesicles (pinched off parts of the membrane (78-79)
o Examples are:
 1. Endocytosis
 Substance taken in and the membrane folds around it (‘coated pit’); clathrin is
the protein coating on the face of the vesicle – cytoplasm side; inside fuses with
a endosome which may fuse with a lysosome; recycled to the plasma membrane,
or released on the opposite side via exocytosis
 Examples: lymphocytes (phagocytosis) destroy bacteria and other microscopic
pathogens
 2. Exocytosis
 Anything produced by the cell (hormone, NT, wastes) to be secreted
 Transmembrane proteins called V-Snares dock with plasma membrane
SNARES and form the vescicle