Antibiotics (Cambridge (CIE) AS Biology): Flashcards
Exam code: 9700
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- FrontPenicillin
Define antibiotic.
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Cards in this collection (16)
Define antibiotic.
An antibiotic is a chemical, made by microorganisms, that kills or inhibits the growth of bacteria.
How does penicillin act on bacteria?
It prevents the synthesis of cross-links in the bacterial cell wall.
The weakened wall cannot withstand the pressure as water enters by osmosis, so the cell bursts (lysis).
Why does penicillin only affect actively growing bacteria?
Penicillin stops new cell wall material from forming.
Only dividing cells are building new wall, so cells that are not growing are unaffected.
Why do antibiotics not affect viruses?
Viruses have no cell wall, ribosomes or metabolic machinery of their own — they use the host cell's.
Antibiotics target bacterial structures and processes that viruses do not have.
Penicillin works by weakening the bacterial cell , causing the cell to burst.
Penicillin works by weakening the bacterial cell wall, causing the cell to burst.
True or False?
Antibiotics can be used to treat HIV.
False.
HIV is a virus, and antibiotics only work against bacteria.
Define antibiotic resistance.
Antibiotic resistance is when bacteria are able to survive exposure to an antibiotic that would normally kill them.
How does antibiotic resistance arise in a population of bacteria?
A random mutation gives some bacteria a resistance allele.
When the antibiotic is used, resistant bacteria survive and reproduce (natural selection), so the resistant type becomes more common.
How can resistance genes spread between bacteria?
By the transfer of plasmids carrying the resistance gene (conjugation), so resistance can pass even between different species of bacteria.
Antibiotic resistance first arises by a random in bacterial DNA.
Antibiotic resistance first arises by a random mutation in bacterial DNA.
True or False?
Using antibiotics creates the mutations that make bacteria resistant.
False.
Mutations occur randomly. The antibiotic does not cause them — it selects for bacteria that are already resistant.
What are the main consequences of antibiotic resistance?
Infections become harder or impossible to treat.
Illnesses last longer and spread more, causing more deaths, higher healthcare costs, and making routine surgery riskier.
What steps can doctors and patients take to reduce antibiotic resistance?
Only prescribe antibiotics when necessary (not for viral infections).
Always finish the full course, and use the correct, specific antibiotic.
Besides careful prescribing, what steps reduce the spread of resistance?
Good hygiene and isolating infected patients in hospitals.
Reducing antibiotic use in agriculture, and rotating the types of antibiotic used.
To reduce resistance, patients should always complete the full of antibiotics.
To reduce resistance, patients should always complete the full course of antibiotics.
True or False?
Antibiotics should be prescribed for a cold or flu.
False.
Colds and flu are caused by viruses, so antibiotics have no effect. Prescribing them only encourages resistance.
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