Final answer:
Polymyxin B binds to the lipid bilayer of the cytoplasmic membrane in gram-negative bacteria, disrupting both their outer and inner membranes and leading to bacterial cell death, but with potential side effects on the kidney and nervous system.
Step-by-step explanation:
The agent from the provided options that binds to the lipid bilayer of the cytoplasmic membrane allowing injurious chemicals to enter is Polymyxin B. Polymyxins are a type of lipophilic polypeptide antibiotic that target the bacterial membrane as their mode of action. They interact directly with the lipopolysaccharide component of the outer membrane of gram-negative bacteria, disrupting both their outer and inner membranes, leading to the death of bacterial cells. Unfortunately, due to their mechanism of action, these drugs can have serious side effects, including potential damage to cells in the kidney and nervous system.