**Title: Effect of Carrier Antibiotics on Lipid-Bilayer Membrane Conductance**Some antibiotics act as carriers that bind an ion on one side of a membrane, diffuse through the membrane, and release the ion on the other side. The graph below illustrates the conductance of a lipid-bilayer membrane containing a carrier antibiotic, as a function of temperature.**Graph Explanation:**- **Y-Axis (Vertical):** Conductance- **X-Axis (Horizontal):** Temperature (°C) ranging from 36°C to 40°C- **Graph Line:** A red curve shows a decrease in conductance as the temperature decreases from 40°C to 36°C.**Conclusion Question:**What can you conclude about the effect of a carrier antibiotic on the conductance of the lipid-bilayer membrane?**Options:**- ○ A carrier antibiotic decreases the conductance of a lipid bilayer, regardless of temperature.- ○ A carrier antibiotic can shuttle ions across a membrane only when the lipid bilayer is quite rigid.- ○ A carrier antibiotic increases the conductance of a lipid bilayer, regardless of temperature.- ○ A carrier antibiotic can shuttle ions across a membrane only when the lipid bilayer is highly fluid.

The fluidity of lipid bilayer membranes increase with an increase in temperature. So, a decrease in temperature will lead to the lipid bilayer membrane becoming less fluid i.e. more rigid.The carrier antibiotic in question has the ability to bind to an ion on one side of a membrane and then diffuse through the lipid bilayer membrane and then release the ion on the other side of the membrane. From the graph, it is evident that the conductance is high at higher temperatures and conductance decreases as the temperature decreases. At higher temperatures, the lipid bilayer membrane is highly fluid while the membrane becomes more rigid as the temperature decreases. Diffusing through a highly flyid membrane is easier compared to diffusing through a rigid membrane.Conductance by the carrier antibiotic through the lipid bilayer membrane is dependent on temperature and conductance increases as temperature increases. So, options 1 and 3 are incorrect.The carrier antibiotic shuttles the ions through the membrane when the membrane is highly fluid (i.e. at higher temperatures). The conductance decreases as the membrane becomes more and more rigid. So, option 4 is correct while option 2 is incorrect.So, the correct option is, A carrier antibiotic can shuttle ions across a membrane only when the lipid bilayer is highly fluid.