How Antibiotics Kill Bacteria

What are Bacteria and Viruses

Bacteria are prokaryotic organisms that are composed of only one cell. This means that they do not have specialized organelles or a cell nucleus with a membrane. Bacteria can be found everywhere around us, including in and on our bodies, and although we like to think of bacteria as always wanting to come after us and harm our bodies, many types of bacteria are actually not harmful. For example, there are many types of bacteria in our intestines that are able to boost our digestive system. For the harmful bacteria however, they cause infections and illnesses like strep throat. Antibiotics can be used to combat bacteria, although some bacteria of have developed resistance against types of antibiotics.

As for viruses, they are even smaller than bacteria. They replicate and use the organelle of the hosts that they infect to replicate, and can affect both eukaryotic and prokaryotic cells. They can cause illnesses through their invasion. Antibiotics don't work on viruses because viruses insert their genetic information into a cell they invade to reproduce, antibiotics have nothing to target in viruses, as they have almost nothing besides some genetic material.

What are Antibiotics?

Antibiotics are antimicrobial drugs that fight infections caused by bacteria. They can fight infections by killing bacteria through targeting aspects of cells that only bacteria can have or prevent them from reproducing, leading to the bacteria just slowly dying off, being unable to reproduce. Unfortunately, antibiotics cannot target viruses, because viruses are mostly made up of genetic material, which antibiotics could not target. There are certain side effects from antibiotics however, as they can harm beneficial bacteria as well as the infectious types, causing you bodily harm if the consumer uses too many antibiotics.

Types of Common Antibiotics Include: Penicilins, Quinolones, Macrolides and Cephalosporins.

Macrolides affect ribosomes, which build proteins for the cells. They target certain parts of bacteria ribosomes that eukaryotic cells do not have. Macrolides only block bacterial ribosomes, but since eukaryotic cells don't have the part that allows macrolides to bind with and inhibit bacteria ribosomes, the human cells are usually left alone. However, macrolides also can kill benificial bacteria too. Macrolides are most effective against respiratory and skin infections.


Quinolones include antibiotics like ciprofloxacin and levofloxacin. They are used to treat infections like bronchitis and pneumonia. Quinolones are able to damage the bacteria's DNA, so when they attempt to replicate and reproduce, they cannot, as they have no DNA. This causes the bacteria to slowly die off.

Bacterial cells have a cell wall, while human cells only have a liquidlike cell membrane. Penicilin is able to target this difference, and the penicilin molecules interfere with part of the synthesis of the bacteria cell wall. It inhibits the synthesis of peptidoglycan, which prevents the bacteria from building and modifying the cell wall. This causes the bacteria to burst because of pressure from osmosis.

Antibiotic Resistance
Antibiotic resistance occurs when a certain bacteria has a mutation in its DNA. When new organelle are synthesized from the DNA, the new antibiotic molecules can not bind and inhib the organelle's function. Because of this, the bacteria is able to survive, when it's fellow bacteria all perish from the antibiotic. It is then able to reproduce, and the resistant bacteria can slowly spread, until the entire type of that bacteria has become resistant to that antibiotic.

More Information

List of Antibiotics
Penicilin Uses
Antibiotic Resistance

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