why are reduced cysteine residues more likely to be found on the cytoplasmic sid - (May/05/2007 )

AS i have read many different journals, many membrane proteins contain several cysteine residues which are located in regions exposed to cytoplasmic side and it said that the reduced status of these cysteine residues is essential for the stability of the proteins.

I want to ask
1. Why are reduced cysteine residues more likely to be found on the cytoplasmic side but not the extracellular side of membrane protein?

2. How can the reduced cysteine residues have the stability function?

THanks

cytoplasmic side pH favours reduction, also much more likely to pick up H+ from the surrounding environment

Stability - reduced form is SH (as opposed to S-), and so is less reactive.