electrochemical gradients

what is the average distance of water molecules

2.8A

• short distance before bumping into one another

why do ions spread out

• constant thermal agitation

• proportional to area of interface and conc gradient

• dependent on dimensions molecules move in (3d is fastest, less chance of bumping)

example of movement for each dimension

• 1D - movement of transcription factors

• 2D - movement in a membrane, catalysts, signalling molecules

• 3D - movement in lipids (cytosol, extracellular fluid)

advantage of signalling molecules and catalysts havin 2d surface

• molecules have more chance of interacting

electrophoretic movement

• movement of ions under the influence of electric field

• additive or subtractive from diffusion

electrochemical gradient

• total gradient = gradient caused by diffusion - gradient caused by electrophoretic movement

ohms law

V = IR

what is rate of movement of ions determined by

• size of electrochemical gradient

• nature of ion - size, charge

• number of open ion channels

• properties of ion channel

current

flow of ions

voltage/potential difference

gradient between to compartments