Cell Biology Laboratory #3 Enzymes：细胞生物学实验室# 3酶.docVIP

Cell Biology Laboratory #3 Enzymes Many chemical reactions in biology are not able to proceed on their own. Instead, they need a catalyst in order for the reaction to proceed normally. In biology there are certain proteins that play an important role as catalysts. We call these proteins enzymes. In many cases in Biology, enzymes act to break down really large molecules into their smaller components. For an example of how an enzyme functions in biology, let’s take a brief look at digestion. A large portion of the nutrients in a potato is starch, which is made by combining many molecules of glucose to form a chain. Our cells use glucose as a source of energy, however, in order to obtain the glucose, the starch must be broken down. However, the starch is a stable compound and does not break down naturally. This requires the work of enzymes. The enzyme that breaks down starch is amylase and is found in amylase. The amylase enzyme will catalyze the breakdown of the starch, resulting in free glucose molecules, which our cells can use. Since the enzyme is a catalyst, it is not consumed in the reaction. In other words, the enzyme that was present at the start of the reaction, is the enzyme, we retain at the end of the reaction. How Enzymes Catalyze Chemical Reactions As stated previously, and enzyme is a certain type of protein that catalyzes chemical reactions, such that these reactions can occur, when they otherwise would not. Again, consider the reaction: Starch ( Glucose This reaction is catalyzed by amylase. The initial reactant is the starch. When we are dealing with reaction requiring enzymes, we call the initial reactant, the substrate. The enzyme binds the substrate in specific place called the active site. This is where the chemical reaction will take place. Once the reaction has taken place, we are left with product. In the example explained above, this is the glucose. Therefore, to review: Starch