Chapter 19, Problem 20CQ

Membranes ii living cells, including those in humans, are characterized by a separation of charge across the membrane. Effectively, the membranes are thus charged capacitors with important functions related to the potential difference across the membrane. Is energy required to separate these charges m living membranes and. if so. is its source the metabolization of food energy or some other source?

Figure 19.26 The semi permeable membrane of a cell has different concentrations of ions inside and out. Diffusion moves the K+ (potassium) and CI- (chloride) ions n the directions shown. until the Coulomb force halts further transfer. This results in a layer of positive charge on the outside, a layer of negative charge on the inside, and thus a voltage across the cell membrane. The membrane is normally impeftneabte to Na+ (sodium ions).