The exchange surfaces of the organisms are the site for an exchange of substances or gases. These surfaces mostly lie within the body and protect the exchange tissues. The exchange surfaces of multicellular organisms are lined with epithelial tissues. These tissues have tightly packed cells with little or no intercellular spaces. The epithelial tissues serve to protect the exchange surfaces. Sometimes, these epithelial linings are modified to perform an additional function. The exchange surfaces are finely branched or folded to have a very large area. The digestive, respiratory, and excretory systems all have such exchange surfaces.
An alkylating agent adds an alkyl group to the DNA strand of a specific cell group highly prone to being cancerous. This action is exactly what Cisplatin does by disrupting DNA replication (mitosis) for cancerous cells by inserting itself into a DNA strand.
Covalent bonds are formed when two non metal atoms share an electron. The atoms either give up or gain an electron, due to the outer shell being unstable.
