BIOL 112 Lecture Notes - Fall 2018 Lecture 8 - Active transport, Electrochemical gradient, Membrane transport
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Friday, September 21, 2018
Lipid
Membrane transport
Membrane transport
1. passive transport
•movement of molecules down a concentration gradient that does not require
energy input
•molecules move in both direction but there is net movement of molecules
a. simple diffusion: molecules diffuse directly through the lipid bilayer
b. facilitated diffusion: diffusion of molecules through a protein transporter
-channel mediated
-carrier mediated
2. active transport
•movement of molecules against a concentration gradient using energy
•molecules move in one direction
•antiporter: transport protein that moves 2 molecules in different directions
•symporter: transport protein that moves 2 molecules in the same direction
a. primary active transport: uses ATP directly to move molecules against
concentration gradient. ex: sodium-potassium pump
b. secondary active transport: does not use ATP as energy source; uses
electrochemical gradient. ex: proton pump
Sodium-potassium pump
•concentration of Na+ is higher outside the cell than inside
•concentration of K+ is high inside the cell than outside
•antiporter has 3 binding sites for Na+ and 2 binding sites for K+
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