Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Antibiotics are chemical substances, such as penicillin, produced by microorganisms that kill or inhibit the growth of bacteria (). They do not work against viruses.
Antibiotic Resistance is an example of natural selection. It occurs when a population of bacteria is exposed to an antibiotic, and individuals with a specific genetic mutation survive and reproduce.
The process of resistance follows the path: . A random mutation in the bacterial provides a survival advantage.
Bacteria can share resistance genes through Horizontal Gene Transfer, often involving the exchange of (small, circular molecules) between different bacterial cells.
Selection Pressure: The overuse of antibiotics in medicine and agriculture increases the 'selection pressure,' allowing resistant strains like () to become dominant.
Incomplete courses of antibiotics contribute to resistance because the weaker bacteria are killed first, leaving the more resistant ones to multiply: .
📐Formulae
💡Examples
Problem 1:
A scientist is testing the effectiveness of an antibiotic. On an agar plate, the 'Zone of Inhibition' (the clear area where bacteria cannot grow) has a radius of . Calculate the area of this zone using .
Solution:
Using the formula for the area of a circle:
Explanation:
The Area of Inhibition represents the efficacy of the antibiotic; a larger area () generally indicates that the bacteria are more sensitive (less resistant) to the drug.
Problem 2:
If a single resistant bacterium () survives a dose of antibiotic and divides every minutes, how many resistant bacteria will be present after hours?
Solution:
First, calculate the number of generations (): Now, use the growth formula:
Explanation:
Because bacteria reproduce through binary fission, the population grows exponentially (). In just hours, a single survivor can produce resistant offspring.