Infection & ResponseDefinitions

Key Definitions

Part of Antibiotics and Drug Resistance · GCSE GCSE Biology revision

This definitions covers Key Definitions within Antibiotics and Drug Resistance for GCSE Biology. Antibiotic function, bacterial resistance evolution, responsible use, global health impact It is section 13 of 18 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.

Topic position

Section 13 of 18

Practice

23 questions

Recall

12 flashcards

Key Definitions

Antibiotic: A chemical substance that kills bacteria (bactericidal) or inhibits their growth (bacteriostatic). Examples include penicillin, amoxicillin, and tetracycline. Antibiotics are ineffective against viruses.

Antibiotic resistance: The ability of a bacterium to survive exposure to an antibiotic that would normally kill it or inhibit its growth. Results from natural selection favouring bacteria with resistance-conferring mutations.

Natural selection: The process by which organisms with advantageous heritable traits survive and reproduce at higher rates than those without, leading to changes in allele frequency in the population over time.

Mutation: A random, spontaneous change in the DNA sequence of an organism. In bacteria, rare mutations can confer antibiotic resistance (e.g., producing an enzyme that destroys the antibiotic).

MRSA (Methicillin-Resistant Staphylococcus aureus): A strain of Staphylococcus bacteria that has developed resistance to methicillin and many other antibiotics. A major cause of difficult-to-treat hospital infections.

Selection pressure: An environmental factor (such as an antibiotic) that affects the survival and reproduction of organisms with different traits, driving natural selection.

Zone of inhibition: A clear area around an antibiotic disc on an agar plate where bacteria cannot grow because the antibiotic has diffused into the agar and killed or inhibited them. Larger zones indicate more effective antibiotics.

Plasmid: A small circular piece of DNA found in bacteria, separate from the main chromosome, that can carry resistance genes. Plasmids can be transferred between bacteria (horizontal gene transfer), spreading resistance rapidly.

Double-blind trial: A clinical trial in which neither the patient nor the doctor knows who receives the real drug or the placebo, eliminating bias from both sides.

Placebo: A dummy treatment that looks and feels identical to the real drug but contains no active ingredient. Used as a control in clinical trials to separate the true effect of the drug from the placebo effect (improvement due to believing you are being treated).

Pre-clinical testing: The stage of drug development that takes place before human trials, including testing on cells and tissues (in vitro) and on animals (in vivo), to check for safety and toxicity.

Clinical trial: A staged series of tests on human volunteers and patients (Phase 1, 2, and 3) carried out to determine the safety and effectiveness of a new drug before it can be approved for use.

Keep building this topic

Read this section alongside the surrounding pages in Antibiotics and Drug Resistance. That gives you the full topic sequence instead of a single isolated revision point.

How It Works: Natural Selection Driving Antibiotic Resistance Common Misconceptions From Miracle Cure to Modern Crisis Key Facts About Antibiotics

Practice Questions for Antibiotics and Drug Resistance

What do antibiotics kill or stop growing?

A. Viruses
B. Bacteria
C. Fungi
D. All pathogens

1 markfoundation

Explain how antibiotic resistance develops in bacteria through natural selection. (3 marks)

3 marksstandard

Quick Recall Flashcards

Why do antibiotics NOT work against viruses?

Antibiotics target bacterial cell walls and bacterial processes. Viruses do not have cell walls and use the host cell's own machinery to reproduce. There is nothing for the antibiotic to target in a virus.

What are antibiotics and what do they target?

Antibiotics are chemicals that kill bacteria or stop them from growing. They target structures that bacteria have but human cells do not, such as cell walls. Examples: penicillin, amoxicillin, streptomycin.

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How It Works: Natural Selection Driving Antibiotic Resistance

Common Misconceptions