(5) c. An E. coli cell has a cytoplasmic pH of 7.2-7.8. This pH value is a resul

Question

(5) c. An E. coli cell has a cytoplasmic pH of 7.2-7.8. This pH value is a result of both active and passive mechanisms required for the ability of E. coli to colonize the human gastrointestinal tract that contains niches of pH ranging from 4.5 to 9. A passive mechanism for maintaining this pH relies on what is termed the buffering capacity of the cell.

(5) d. The no. of moles of RNH4+ in the extracellular liquid (i.e. above the cells) = 10-6 mol

The volume of liquid above the cells (i.e. extracellular liquid) = 10 mL = 10/1000 L = 10-2 L (since 1 L = 1000 mL)

(Note: 1 M = 1 mol/L)

Therefore, the concentration of RNH4+ in the extracellular liquid = 10-6 mol / 10-2 L = 10-4 M

(5) e. The no. of moles of RNH4+ in the cells) = 10-5 mol

The volume of liquid in the cells = 1 mL = 1/1000 L = 10-3 L

Therefore, the concentration of RNH4+ in the extracellular liquid = 10-5 mol / 10-3 L = 10-2 M

Explanation / Answer

eain es .t catai auaie to stimate the intermal pli in a cell ing centrifugation, we can measure the final volume of cells from the f the following procedure is to estimate the internal pi in a cell. volume of packed cells, and we can measure the volume of extracellalar liou r from the volume of liquid above the cells. The final volume of cells is I ml volume of liquid above the cells is 10 ml. At pH's which are well below total amount of RNH in the liquid above the cells is 10-6 moles amount of RNHs' in the cells if 10-5 moles. Answer (5) c. Why does the pH have to be well below 9 for in less than 50 word. this method to work? (5)d. What is the concentration of RNHs in the extracellular liquid (5)e. What is the concentration of RNH4 in the cells'?

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