Highlights Enzymes II

1. Enzymes work by lowering activation energies of reactions. They do NOT alter the energies of the molecules in the reactions. They change the energy necessary for the reaction to occur. Consequently substrates and products are at the same energies in both enzymatic and non-enzymative reactions.

2. Important classes of enzymes include amylases(break down carbohydrates), pectinases (break down pectins), and proteases (break down proteins).

3. It is advantageous to immobilize enzymes. This allows one to pass solutions of substrate over the immobilized enzymes and capture product without having to purify the enzyme away from the product. If handled carefully, immobilized enzymes can be used for extended periods of time.

4. One example of an immobilized enzyme is to enclose it in a membrane. Systems like this can employ more than one enzyme so that two interdependent enzymatic reactions can occur. In the example given in class, one reaction produced NADH, which was necessary for the other enzymatic reaction to occur.

Recombinant DNA

1. The discovery of the structure of DNA in 1953 was one of the most important scientific discoveries of the 20th century. Though James Watson and Frances Crick were credited with the discovery, a third person, Rosalind Franklin discovered one of the central pieces of data necessary for the structural determination.

2. Rosalind Franklin's data was given to Watson and Crick at a scientific meeting in England that Linus Pauling was unable to attend due to politics over his visa.

3. DNA has a double helical structure with adenines (A) paired with thymine (T) and guanine (G) paired with cytosine (C).

4. DNA has two grooves in it - a major one that is wide and a minor one that is narrow.

5. In the determination of the structure of DNA, one piece of information is often ignored. Erwin Chargoff made the observation that the amount of C in a DNA equaled the amount of G and the amount of A equaled the amount of T. Watson and Crick used this information to determine that base pairs existed.

6. DNA is replicated prior to cell division. Replication of DNA requires an enzyme called a DNA polymerase and it is shaped something like a hand.

7. The polymerase chain reaction (PCR) is a technique that uses the principles of DNA replication to make millions of copies of a desired sequence in hours. Part of the PCR process involves boiling the solution. A special DNA polymerase isolated from Thermus aquaticus (a bacterium that lives in boiling water environments) is used. It does not get invactived by the boiling and simplifies (and speeds) the process.