Why Does the Structure of Gramicidin, Shown Below, Only Allow

Question

Why does the structure of gramicidin, shown below, only allow topical use as an antibiotic? 
A) synthesis of nucleic acid 
B) synthesis of cell wall 
C) beta lactam rings 
D) DNA synthesis 
E) It creates channels in cell membranes.

Accepted Answer

The structure of gramicidin allows it to create channels in cell membranes, which disrupts the integrity and functionality of the cell. This mechanism of action is only effective when gramicidin is applied topically, as the channels would not be specific to harmful bacteria and could potentially harm beneficial bacteria in the gut if taken orally. Gramicidin does not affect the synthesis of nucleic acid, cell wall, or beta lactam rings, nor does it inhibit DNA synthesis.