Tutor profile: Zvi C.
Subject: Organic Chemistry
What is the difference between an Sn1 reaction and an Sn2 reaction?
Sn1 and Sn2 reactions are two different types of nucleophilic substitution reactions, which is a reaction in which one molecular (nucleophile) forms a bond with another molecule (electrophile) and causes it to unbond with on of its functional groups (leaving group). In an Sn1 reaction, the electrophile loses its leaving group before the nucleophile forms a bond with it. In an Sn2 reaction, there is a simultaneous bonding of the nucleophile and unbinding of the leaving group from the electrophile. The likelihood of an Sn1 or Sn2 nucleophilic substitution depends on the chemical characteristics of the reactants, for example the stability of the electrophile after it loses its leaving group (carbocation). If the carbocation is very stable, then an Sn1 reaction will be favored. If not, the Sn2 reaction will be favored.
Subject: Biomedical Science
What is cancer?
Cancer is the uncontrolled division of cells within our bodies. When we are healthy, our cells listen to our body's direction and have appropriately timed and controlled cell division. However, cells can accumulate mutations in their DNA, which cause the cells to stop listening to our body's directions. Mutations can be caused by environmental agents such as tobacco smoke, radiation and the sun. Eventually the tumor (a ball of cells dividing) can invade into the blood and spread throughout the body, a process called metastasis. In fact, most cancer deaths are due to the tumors that were spread from the initial organ with cancer.
What does an enzyme do?
An enzyme is a type of protein that speeds up certain chemical reactions inside the cell, a process call catalysis. These reactions can range from breaking up a glucose molecule, to attaching phosphates to other proteins. Enzymes are composed of strings of amino acids.
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