Under anaerobic conditions in some bacteria such as E. coli , F1Fo-ATP synthase
ID: 147015 • Letter: U
Question
Under anaerobic conditions in some bacteria such as E. coli, F1Fo-ATP synthase operates in reverse and hydrolyzes MgATP to establish and maintain a pH gradient across the plasma membrane. The potential energy of the proton gradient then drives secondary transporters such as the “lactose permease”, a member of the major facilitator superfamily (MFS) of transporters. Lactose permease (LacY) exits in two conformations referred to as outward and inward facing. The outward facing conformation has high affinity for lactose and when protonated, the transporter will change to the inward facing conformation and release lactose and the proton into the cytoplasm.
(a) Assume a situation where the F-ATPase hydrolyzes MgATP (runs in reverse) to establish a pH of 5 in the periplasm, and that the pH in the cytoplasm is 7.2. Using the Nernst equation, calculate the associated membrane potential in mV? (Assume that there are no other ion gradients across the plasma membrane)
(b) What is the proton motive force (H+) of above pH gradient? Show your work!
Explanation / Answer
1)the equillibrium potential is a membrane potential where the net flow through any open channels is zero.in otherwords at Erev,the chemical and electrical forces arein balance.
nernst equation..sodium +60,mg/Na -88mV...
2)electron motive force occurs when the cell membrane becoms energized due to electron transport reactions by the electron carries embeded in it.
the energy expressed here as gibbs free energy ,PMF is a combination of 2gradients across the membrane the concentration gradient and electric potential gradient.
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