Running Head: UNIT 2 – CELL
BIOLOGY
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Cell Biology: How Antibiotics Stop Bacteria Without Harming Human Cells
Amanda L. Wood
American Intercontinental University
UNIT 2 – CELL BIOLOGY
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Cell Biology: How Antibiotics Stop Bacteria Without Harming Human Cells
To better understand how antibiotics work to treat bacteria without harming human cells,
we first need to understand what bacteria is, and what antibiotics are. According to
https://biologydictionary.net/bacteria/, bacteria are single-celled microorganisms with
prokaryotic cells, which are single cells that do not have organelles or a true nucleus and are less
complex than eukaryotic cells. Bacteria with a capital B refers to the domain Bacteria, one of the
three domains of life. The other two domains of life are Archaea, members of which are also
single-celled organisms with prokaryotic cells, and Eukaryota. Bacteria are extremely numerous,
and the total biomass of bacteria on Earth is more than all plants and animals combined.
Antibiotics are described as a type of agent that can kill or stop the growth of
microorganisms, often administered to treat bacterial infections. This is also referred to as an
antimicrobial agent. Human cells do not have cell walls as they are eukaryotic and contain a
nucleus while bacteria do not. Bacteria and human cells also differentiate regarding their
structure as well. There are a wide range of antibiotics that treat bacterial infections, but we will
only discuss penicillin, tetracycline, chloramphenicol, sulfonamides, and vancomycin here. How
do these antibiotics treat bacterial infections without harming human cells?
Penicillin’s are a group of antibacterial drugs that attack a wide range of bacteria
(Newman, 2019). Drugs in this class work by blocking or bursting bacterial cell walls. No
harm comes to the human host because penicillin does not inhibit any biochemical process that
goes on within us.
Tetracyclines are antimicrobials that target bacteria by blocking protein synthesis
and it is used often used in veterinary medicine. Both bacteria and humans carry out protein
synthesis on structures called ribosomes. Tetracycline can cross the membranes of bacteria and
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accumulate in high concentrations in the cytoplasm. Tetracycline then binds to a single site on
the ribosome--the 30S (smaller) ribosomal subunit--and blocks a key RNA interaction, which
shuts off the lengthening protein chain. In human cells, however, tetracycline does not
accumulate in enough concentrations to stop protein synthesis (Mobley, 2018).
Rarely used now due to serious and fatal reactions, Chloramphenicol diffuses
through the bacterial cell wall and reversibly binds to the bacterial 50S ribosomal subunit. The
binding interferes with peptidyl transferase activity, thereby prevents transfer of amino acids to
the growing peptide chains and blocks peptide bond formation. As a result, bacterial protein
synthesis is blocked and impede bacterial cell proliferation.
Sulfonamides are antibiotics that target and inhibit folic acid synthesis. Human
cells do not synthesize folate, therefore sulfa drugs do not harm them.
Vancomycin is an antibiotic that blocks the construction of bacterial cell walls,
which eukaryotic cells do not have. Therefore, they are also not harmful to human cells.
Bacterial infections and Viral infections are different because bacteria are a living
organism, but a virus is not. A virus cannot even function without first taking over a host cell
because it has no cell structure. Bacteria make up a large domain of prokaryotic organisms while
viruses are smaller and can only replicate inside other living cells. Viruses do not consist of
ribosomes where protein synthesis takes place, while bacteria do have ribosomes. The structure
of bacteria and viruses also differentiate in their structures. Bacteria structures consist of freefloating DNA and RNA which are in the cytoplasm. Virus structures consist of DNA and RNA
which is coated in a protein.
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So since we know that antibiotics work by either stopping the growth of bacterial cells or
killing them, it would make sense that these medications would not be beneficial in treating viral
infections because viruses are not living and there is no cure for them, as they are all considered
harmful. Vaccines can help prevent the spread of viruses and slow the reproduction of them, but
it cannot stop viruses completely since they replicated and are extremely more abundant than
bacteria (Aryal, 2015).
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References
National Center for Biotechnology Information. PubChem Database. Chloramphenicol,
CID=5959, https://pubchem.ncbi.nlm.nih.gov/compound/Chloramphenicol (accessed on Oct. 18,
2019)
Mobley, H. (2018). How do antibiotics kill bacterial cells but not human
cells? Retrieved from: https://www.scientificamerican.com/article/how-do-antibiotics-kill-b/
Aryal, S. (2015). Differences between bacteria and viruses. Retrieved from:
https://microbiologyinfo.com/differences-between-bacteria-and-viruses/
https://biologydictionary.net/bacteria