A Level Biology Practice Exam 2026 - Free A Level Biology Practice Questions and Study Guide

Selective toxicity is a crucial concept in the field of pharmacology and microbiology, particularly in the development and use of antimicrobial agents. It refers specifically to the ability of a drug or treatment to target and disrupt the processes of a pathogen, such as bacteria, viruses, or parasites, while having minimal or no effect on the host's own cells. This targeting is fundamental for the effectiveness of antibiotics, chemotherapy, and other therapeutic agents, as it allows for the elimination of harmful organisms without causing significant harm to the patient.

For instance, many antibiotics function by exploiting differences between prokaryotic (bacterial) and eukaryotic (human) cells, such as differences in cell wall composition or metabolic pathways. This selectivity allows for effective treatment of infections while preserving the integrity and function of human tissues.

The other options do not accurately capture the essence of selective toxicity. Increasing the growth rate of host cells or describing a general property of organisms to resist infections does not relate to the targeting of pathogens in a therapeutic context. Similarly, a selection process by which host cells eliminate pathogens does not reflect the targeted action of drugs, but rather immune responses which are a different biological process. Thus, the first option encapsulates the meaning of selective toxicity brilliantly.