Group Translocation - Online Tutor, Practice Problems & Exam Prep

Group translocation is a unique transport mechanism exclusive to bacteria, where a molecule is chemically modified as it enters the cell. This process typically involves the addition of a phosphate group from a high-energy molecule, allowing the modified molecule to be transported down its concentration gradient. For example, in the E. coli phosphotransferase system, glucose is converted to glucose 6-phosphate during transport. This modification maintains a higher concentration of glucose outside the cell, facilitating continuous uptake. Group translocation is often categorized as a form of active transport due to the energy requirement for modification.

Group Translocation

In this video, we're going to begin our introduction to group translocation. Group translocation is a special type of transport across the membrane where a molecule is chemically modified as it enters the cell. Typically, group translocation results in the addition of a phosphate group from a high-energy molecule to the molecule that's entering the cell. The modification to the entering molecule allows it to always be transported down its concentration gradient, from high to low. Group translocation is a transport process exclusive to bacteria; only bacteria perform group translocation.

Let's take a look at this image below, which shows an example of the E. coli phosphotransferase system (PTS system). This system transfers glucose into the cell and converts it into glucose-6-phosphate as the glucose is being transported into the cell. Notice that glucose is represented by green hexagons. Here we have our biological membrane, and within the membrane, there is a transporter. As glucose enters the cell, it is chemically modified. The high-energy molecule, labeled as such, has a phosphate group on it. This phosphate group is transported over to glucose specifically on glucose's sixth carbon, forming glucose-6-phosphate. As glucose enters the cell, it is chemically modified to become glucose-6-phosphate. This modification means that the glucose outside the cell remains in a higher concentration compared to the inside. Because glucose is different from glucose-6-phosphate, they will have different chemical gradients. As glucose enters the cell and is chemically modified, the concentration of plain glucose will always be lower inside the cell and higher outside, allowing the cell to continuously uptake glucose.

Group translocation is a type of membrane transport where a molecule is modified as it enters the cell. Scientists sometimes categorize group translocation as a special or alternative type of active transport because a high-energy molecule is needed to chemically modify the molecule entering. This concludes our brief introduction to group translocation. We'll be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.

During group translocation, which statement is true?

• A. No energy is required.
• B. Substrate is being modified.
• C. Channel is an integral membrane protein.
• D. Both b and c.

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.

Here’s what students ask on this topic:

What is group translocation in bacteria?

Group translocation is a unique transport mechanism exclusive to bacteria, where a molecule is chemically modified as it enters the cell. This process typically involves the addition of a phosphate group from a high-energy molecule, allowing the modified molecule to be transported down its concentration gradient. For example, in the E. coli phosphotransferase system, glucose is converted to glucose 6-phosphate during transport. This modification maintains a higher concentration of glucose outside the cell, facilitating continuous uptake. Group translocation is often categorized as a form of active transport due to the energy requirement for modification.

How does the phosphotransferase system (PTS) work in E. coli?

The phosphotransferase system (PTS) in E. coli is a classic example of group translocation. In this system, glucose is transported into the cell and simultaneously phosphorylated to form glucose 6-phosphate. This process involves a high-energy molecule that donates a phosphate group to glucose as it enters the cell. The phosphorylation occurs specifically at the 6th carbon of glucose. This chemical modification ensures that the concentration of unmodified glucose remains higher outside the cell, allowing for continuous glucose uptake. The PTS system is energy-dependent, making it a specialized form of active transport.

Why is group translocation considered a form of active transport?

Group translocation is considered a form of active transport because it requires energy to chemically modify the molecule being transported. In this process, a high-energy molecule, such as phosphoenolpyruvate (PEP), donates a phosphate group to the molecule entering the cell. This energy-dependent modification allows the molecule to be transported down its concentration gradient. Despite the molecule moving from high to low concentration, the energy required for its chemical modification classifies group translocation as active transport.

What is the role of glucose 6-phosphate in group translocation?

In group translocation, specifically in the E. coli phosphotransferase system, glucose 6-phosphate plays a crucial role. As glucose enters the cell, it is phosphorylated to form glucose 6-phosphate. This chemical modification ensures that the concentration of unmodified glucose remains higher outside the cell, facilitating continuous glucose uptake. The formation of glucose 6-phosphate also prevents glucose from diffusing back out of the cell, effectively trapping it inside for metabolic processes. This modification is essential for maintaining the concentration gradient and efficient glucose transport.

What types of molecules are typically involved in group translocation?

Group translocation typically involves small molecules such as sugars, including glucose, mannose, and fructose. These molecules are chemically modified as they are transported into the bacterial cell. For example, in the E. coli phosphotransferase system, glucose is phosphorylated to form glucose 6-phosphate. The modification usually involves the addition of a phosphate group from a high-energy molecule like phosphoenolpyruvate (PEP). This process ensures that the concentration gradient is maintained, allowing for continuous uptake of these essential nutrients.