In pages 74-75 in Chapter 4, Moalem describes free radicals and how they disrupt cellular chemistry which results in cell death and how the G6PD protein is a regulator of free radicals, especially in red blood cells. This relates to Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties by showing the interactions between free radicals and G6PD.
Research a free radical (e.g. superoxide anion, hydroxyl radical, hydrogen peroxide, etc.) and explain how the free radical attacks and mutates a cell's DNA. Also, explain how the G6PD protein defends a cell from a certain free radical. References to cells and DNA are recommended.
(Name: Will Han email: wihan4@students.d125.org)
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ReplyDeleteA hydroxyl radical is a free radical that comes from the decomposition of hydroperoxides. Hydroxyl radicals are highly reactive, since hydroxyl radicals have unpaired electrons. According to an article in “Mutation Research/Fundamental Molecular Mechanisms of Mutagenesis”, hydroxyl radicals can cause DNA to have modified purine and pyrimidine bases. Hydroxyl radicals can also damage DNA by DNA-protein cross-links and abasic sites. DNA-protein cross-links can block DNA replication from occurring. If the crosslink is not repaired, the cell could die. An abasic site is a location in DNA that has neither a purine nor pyrimidine base. According to a journal article from PNAS, hydroxyl radicals can also damage DNA by breaking the DNA strand which can be initiated when the hydroxyl radical abstracts a deoxyribose hydrogen atom.
ReplyDeleteHydroxyl radicals can damage DNA in a variety of ways from crosslinks to physically breaking the DNA strand. The damage to DNA caused by hydroxyl radicals has bad consequences for the cell. For example, since hydroxyl radicals can cause modified purine and pyrimidine bases, the genes of the DNA can’t be expressed properly. A modified DNA base can result in a missense mutation in which the protein expressed by the mutated gene is different from the protein expressed by the normal gene. If a cell produces different proteins than what the cell needs to produce, then the cell will not function properly resulting in the organism not functioning properly either. Hydroxyl radicals can also disrupt DNA replication through DNA-protein cross-links as well as abasic sites. Abasic sites on DNA are known to have negative effects on DNA polymerase. DNA polymerase is the protein that replicates DNA each time a cell divides. Without DNA polymerase working normally, DNA replication will not work normally resulting in complications when the cells divide.
With the many ways that free radicals can damage DNA, there are proteins in the body that help get rid of free radicals. One such protein is called G6PD. According to Dr. Moalem on page 74, G6PD is like a “bouncer in the red blood cell bar: when it’s on the job, it throws out the free radicals so they can’t start trouble”. G6PD protein essentially maintains cellular integrity through getting rid of free radicals and preventing free radicals, like hydroxyl radical, from mutating the DNA and disrupting gene expression. The way free radicals interact with cells relates to Big Idea 3 which states “Living systems store, retrieve, transmit, and respond to information essential to life processes” as cells respond to free radicals through making the protein G6PD to stop free radicals from damaging the DNA and disrupting gene expression.
(Laura Gu, laugu4@students.d125.org)