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movement of mass substances across a membrane
What substances can freely diffuse across a membrane?
What substances can cross a membrane via facilitated diffusion?
A substance moving DOWN its concentration gradient
Def: active transport (primary)
Movement of a substance against its concentration gradient.
Energy required in the form of ATP.
Def: active transport (secondary)
Movement of one substance against its gradient, coupled with movement of another substance down its gradient.
Def: electrochemical potential
Symbolized by (C)
A difference in either electric potential or concentration of a substance across a membrane.
What is flux rate dependent on?
Determined by electrochemical potential (deltaC) and Membrane potential (P)
(P) is a function of what?
Molecular size and membrane partition coefficient, i.e., membrane solubility
What is the partition coefficient (beta)?
the ratio of the [ ] of the substance in the membrane, to [ ] in the aqueous solution in contact with the membrane.
When the C(outside) = C(inside), the partition coefficient (beta) = what?
Beta = 1