Lect 03 F10 - 1 Molecular structure of a K channel From...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 Molecular structure of a K + channel. From Doyle et al. (1998). Science 280: 69-77 Ion Transport through Cell Membranes Some permeability » small nonpolar molecules O 2 (32 daltons molecular mass) CO 2 (44 daltons) » uncharged polar molecules (small) H 2 O (18 daltons) ethanol (46 daltons) glycerol (92 daltons) Virtually impermeable x large uncharged polar molecules x ions and charged molecules (whatever size) (10 9 more permeable to water than to ions) Lipid bilayer are highly impermeable to charged molecules, even if they are small. 2 The movement of ions and small polar molecules across cell membranes is mediated by transport proteins that form aqueous channels. Transport proteins are highly speciFc for particular molecules. The distribution of transporters is a primary determinant of the solute composition of membrane- bounded compartment. Energetics of ion transport. 1) Like other molecules, ions diffuse down their concentration gradient, from high concentration to low concentration. 2) Ions are also charged, and the sum of different ion concentrations on either side of a membrane results in a membrane potential. The transport of ions across a membrane is therefore also inFuenced by their electric charge. 3) The net movement of an ion across the membrane is determined by it’s Electrochemical Gradient = Ion Concentration Gradient + Electric Potential 3 Representative electrochemical gradients of four important ions OUTSIDE INSIDE 145 mM 5-15 mM + + + + + + + + + + + +- - - - - - - - - - - - + + + + + + + + + + + +- - - - - - - - - - - - Na + Ca ++ Cl- K + 10-4 mM 5-15 mM 140 mM 1-2 mM 110 mM 5 mM Strong tendency for both Na + and Ca ++ to inFux into cells down their steep electrochemical gradients....
View Full Document

{[ snackBarMessage ]}

Page1 / 11

Lect 03 F10 - 1 Molecular structure of a K channel From...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online