This means that the transport of cations into the cell will be favoured over the transport of anions which would increase this potential. The biggy is ATP hydrolysis, but this is sometimes indirect, as we'll see. G is for the hydrolysis of the ATP in this case, or the thermodynamically favoured reaction 4. Passive Transport let's start to look now at the different kinds of transport that occur in biological systems. The simplest kind of transport is called passive diffusion or passive transport.
Ions have high P values, whereas water has a rather low value.
It is not clear why the permeability to water is so high, since you would think that it would not be favourable for the polar water molecule to pass through the non-polar environment. Facilitated Transport clearly something else is at work here other than simple passive diffusion. The other kind of thermodynamically favoured transport, that does not involve coupling of any kind is facilitated transport or diffusion. The movement is still driven by a concentration difference exclusively, but it is helped by specific transporters. There are two types of these, pores and carriers facilitated transport through pores occurs when a specific pore molecule or complex of molecules allows passage of molecules or ions very specifically these pores are very specific, and only the molecule of choice passes.