Lect23.ChannelsPumps - LECTURE 23: Membrane Pumps,...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
LECTURE 23: Membrane Pumps, Cotransporters and Channels Reading: Berg, Tymoczko & Stryer: Chapter 13 Lipid membranes are barriers to diffusion of aqueous-soluble molecules PUMPS move molecules uphill AGAINST their concentration gradients Pumping is rendered energetically favorable by ACTIVE TRANSPORT: The coupling to an expenditure of energy, such as hydrolysis of ATP COTRANSPORTERS couple the passage of molecule A across a membrane to the passage Of molecule B across membrane in same or opposite direction Transport of molecule A uphill AGAINST its gradient is made energetically favorable By coupling to molecule B transport down its gradient CHANNELS allow passage of molecules downhill from high-to-low concentration Process is energetically favorable, and is called PASSIVE TRANSPORT or FACILITATED DIFFUSION PUMPS CHANNELS Na + - K + ATPase Gastric H + - K + ATPase Glucose Transporters Voltage-Gated Ion Channels Ligand-Gated Ion Channels COTRANSPORTERS Lactose Permease Na + - Ca + Exchanger
Background image of page 1

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

View Full DocumentRight Arrow Icon
Biological Functions of Pumps Increase concentration of an ion to enable a biochemical process (e.g., gastric proton ATPase lowers pH to favor food-digesting proteases) Decrease concentration of an ion to prevent a biochemical process (e.g. muscle sarcolemmal Ca+ - ATPase pumps calcium out of muscle cytoplasm to allow for muscle relaxation) Generate molecule concentration gradients that serve as energy reservoirs for subsequent physiological processes The free energy stored in a concentration gradient is quantifiable: G = 2.3RT log 10 (c out /c in ) When the pumped molecule is charged, both concentration gradient and voltage across the membrane determine the stored free energy G = 2.3RT log 10 (c out /c in ) + ZF V
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 17

Lect23.ChannelsPumps - LECTURE 23: Membrane Pumps,...

This preview shows document pages 1 - 3. Sign up to view the full document.

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