Question

E. coli cells transport xylose across the cell membrane via a symport system that uses the free energy of a proton gradient. The intracellular pH is higher than the extracellular pH. (a) Is xylose moving up or down its concentration gradient? Into or out of the cell? (b) Draw a diagram of the xylose transport system.

Short answer

1. The xylose is moving up to its concentration gradient-into the cell.
2. The diagram of the xylose transport system is as follows:

Step-by-step solution

Introduction

Gram-negative bacteria are those like E. coli. Several active transport mechanisms are involved in the transportation of sugars in gram negative bacteria. The pentose phosphate pathway is used to metabolise the xylose, which is used as a carbon source.

In the solution (a), Xylose is moving up to its concentration gradient

The pH of the E. coli cell intracellular environment is greater than the pH of the external environment. This means that outside the cell wall, the proton concentration is higher than within the cell. E. coli requires xylose, which travels up the concentration gradient.

In the solution (b), Pictorial representation of xylose transport system

Along with xylose, the protons move down to their concentration gradient into the cell by a symport system.

Conclusion

As a result, the xylose is ascending the concentration gradient. A symport system transports protons into the cell according to their concentration gradient.