Which of the following statements is TRUE about the E. coli phosphotransferase system (PTS)?

• A. The PTS does not require an input of energy from the cell.
• B. Substrate being transported is phosphorylated during transport from a high-energy molecule.
• C. The PTS requires energy in the form of an ion gradient.
• D. The PTS requires energy in the form of ATP.

Answer: (B)

Verified step by step guidance

1. Understand the role of the phosphotransferase system (PTS) in E. coli, which is a method used by bacteria to transport sugars across the cell membrane while simultaneously phosphorylating them.
2. Recognize that the PTS system involves a series of proteins and enzymes that transfer a phosphate group from a high-energy molecule, such as phosphoenolpyruvate (PEP), to the sugar being transported.
3. Identify that the phosphorylation of the substrate (sugar) occurs during its transport across the cell membrane, which is a key feature of the PTS system.
4. Clarify that the energy required for this process comes from the high-energy molecule PEP, not from ATP or an ion gradient, distinguishing it from other transport systems.
5. Conclude that the true statement about the E. coli PTS is that the substrate being transported is phosphorylated during transport from a high-energy molecule, specifically PEP.