9700 · 10.2
Antibiotics flashcards
Revision flashcards for Cambridge 9700 Antibiotics (syllabus 10.2). Flip, recall, then mark a real past-paper question.
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What is selective toxicity?
The principle that an antibiotic can harm or kill a pathogen (like bacteria) without causing significant damage to the host's cells. This is possible because antibiotics target structures or pathways unique to prokaryotes.
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How does penicillin work?
Penicillin inhibits the enzyme transpeptidase, which is essential for forming cross-links in the peptidoglycan cell wall of bacteria. This weakens the cell wall, leading to cell lysis and death, especially in growing bacteria.
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What is a plasmid?
A small, circular, double-stranded DNA molecule that is distinct from a cell's chromosomal DNA. Plasmids often carry non-essential genes, such as those for antibiotic resistance, and can be transferred between bacteria.
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What is horizontal gene transfer?
The movement of genetic material between organisms other than by vertical transmission (from parent to offspring). In bacteria, it occurs via conjugation, transformation, and transduction, rapidly spreading traits like antibiotic resistance.
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What does MRSA stand for?
Methicillin-resistant *Staphylococcus aureus*. It is a strain of bacteria that has developed resistance to multiple antibiotics, including methicillin and other beta-lactam antibiotics, making it difficult to treat.
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What is a β-lactamase?
An enzyme produced by some bacteria that provides resistance to β-lactam antibiotics like penicillins. It works by breaking the antibiotic's structure (the β-lactam ring), rendering it inactive.
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What is the role of natural selection in antibiotic resistance?
The presence of an antibiotic creates a selective pressure. Bacteria with a random mutation conferring resistance survive and reproduce, while susceptible bacteria are killed. Over time, the frequency of resistant bacteria in the population increases.
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What is an efflux pump in the context of antibiotic resistance?
A protein channel in the bacterial cell membrane that actively transports antibiotics out of the cell. This prevents the antibiotic from reaching a high enough concentration to be effective.