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Name: Sheree
Status: Other
Grade:  Other
Location: NH
Country: United States
Date: September 2005

Why Do antibiotics kill bacteria and not US?

Antibiotics ideally are designed to attack something in the cellular machinery that bacteria have the humans do not. For instance, penicillin interrupts the building of the bacterial cell wall and human cells do not have cell walls. Unfortunately, many antibiotics can be somewhat difficult to take because they end up affecting something in our body like the good bacteria in our intestine. This is just one of the reasons to use antibiotics judiciously.


Great question! Usually, they are directed against a structure of process that bacteria or fungi have that we don't. For example, bacteria have a characteristic cell wall that humans don't have (humans don't have cell walls at all!). Penicillin disrupts cell wall synthesis and causes bacterial cells to burst.


Penecillin, for example, inhibits cell wall synthesis in gram negative bacteria, but since humans don't have a cell wall in is harmless to us, unless you are allergic to it. Streptomycin and its' derivatives bind to bacterial ribosomes and inhibit protein synthesis, but since streptomycin doesn't bind to human ribosomes, again it is harmless to us.

Ron Baker, Ph.D.

Vitamin C (ascorbic acid) is an example of a water soluble anti-oxidant. It reacts with free radicals like atomic oxygen thus stopping the free raical with reacting with DNA and proteins which could damamge your cells. An example of a fat soluble anti-oxidant is Vitamin E. By definition, it is insoluble in water.

Ron Baker, Ph.D.

Antibiotics target differences between bacterial cells and our cells. For example, a bacterial cell may have a protein with a slightly different shape than the same protein in our cells. If an antibiotic binds specifically to a unique "bump" that is found on the bacterial protein, but not found on the human version, then it may kill the bacterial cell by inactivating the protein. Our protein, which does not have the same shape, will not be bound by the antibiotic, and hence, not affected. It's all about exploiting minor differences between bacterial cells and human cells. Paul Mahoney, PhD

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