Question

lets consider part one of the uniport reaction. assume the atp coupling works by having an intermediate step in which atp transfers one phosphate to the transporter. 1 atp + proton pump 2 adp + proton - pump - p 2 adp + proton - pump + p pump is phosphorylated adp pump dephosphorylated for each of the two steps in the reaction, is the δg positive or negative and why? indicate the free energy state of components shown with bar graphs. what energy is available to directly drive transport of protons? lots free energy some a little transporter + atp transporter - p + adp transporter + adp + pi

Explanation:

Step1: Analyze first - step reaction

The first - step reaction is ATP + proton pump → ADP+ proton pump - P. ATP hydrolysis is an exergonic reaction. The free - energy change ($\Delta G$) for ATP hydrolysis is negative because ATP has high potential energy due to its phosphate bonds, and when it donates a phosphate to the proton pump, energy is released.

Step2: Analyze second - step reaction

The second - step reaction is proton pump - P → proton pump+Pi. The de - phosphorylation of the proton pump is also an exergonic reaction. The phosphorylated proton pump is in a high - energy state, and when it loses the phosphate group, energy is released, so $\Delta G$ is negative.

Step3: Determine energy for proton transport

The energy available to directly drive the transport of protons is the free energy released from the de - phosphorylation of the proton pump (the second step). This energy can be used to change the conformation of the proton pump and move protons against their concentration gradient.

Answer:

1. For the first step (ATP + proton pump → ADP + proton pump - P), $\Delta G$ is negative because ATP hydrolysis is exergonic. For the second step (proton pump - P → proton pump+Pi), $\Delta G$ is negative because de - phosphorylation of the proton pump is exergonic.
2. In the bar graph: Transporter + ATP has high free energy, Transporter - P+ADP has intermediate free energy, and Transporter + ADP + Pi has low free energy.
3. The energy available to directly drive transport of protons is the free energy released during the de - phosphorylation of the proton pump (second step).