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^^ just to add on, Lavelle was saying how transplatin is only able to form one bond in DNA (which is weak, so it can't stop cell division), whereas cis platin is able to form 2 bonds in the DNA, causing for the DNA to be interfered with enough to the point of stopping cell division & ultimately, cell death
Cisplatin, unlike transplatin, can bond to the same piece of DNA with two bonds to block DNA replication. This lack of replication can kill cancerous cells. The structure of transplatin makes it so that it can only bond at one site on DNA, which is not strong enough to stop DNA replication.
Cisplatin binds the two strands of the cell's DNA (genetic material) together, and it can't be replicated. If the strands are permanently binded together then DNA helicase won't be able to split the strands and DNA polymerase wouldn't be able to add complementary nucleotides to the lagging and leading DNA strands. So if the cell can't synthesize any more DNA then it won't be able to progress through the cell cycle and divide.
The Cl atoms on the clisplatin molecule bind to the exposed N on two nearby (but not necessarily next to each other) guanine nucleotides, forming a coordination compound with the DNA molecule. The bound cisplatin blocks DNA replication machinery, preventing the DNA from replicating and ultimately stopping cell division.
Cisplatin works by attaching itself to DNA in a way that prohibits its function. It bonds to the guanine and adenine bases so the water molecules originally bound to the platinum fall off, and coordinate covalent bonds to the platinum are formed using a lone pair on the nitrogen atom of two guanines next to each other on the helix. This disrupts the helix and prevents the DNA from replicating.
If you memorize why cisplatin is able to stop DNA replication, and by extension cell division, you should also be able to apply this information to the final. I feel like in the context of the final, the application and memorization of this information is more or less synonymous.
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