A.  Daily Blog

10/13/2010 (submitted 10/18/2010)

Class started in quite a professional manner and atmosphere, literally. Most of the guys were dressed in suits because of International Suit-up Day, and they would take it seriously, haha. Any how, we talked about energy today. The two main types of energies are potential and kinetic. Kinetic energy is the energy of motion. Potential energy is based on structure and position. Heat is the total kinetic energy and temperature is the average kinetic energy, both due to molecular motion. The Laws of Thermodynamics came back in to question. The first law states that energy is never created or destroyed, it just changes forms, and the second law states that entropy is constantly increasing spontaneously. The eventual result of entropy is heat. We as humans contradict this law of energy. Heat for humans is dead energy, it can perform no function. The human body is highly dependent on its gradients and its predominant non-spontaneous organization. It absorbs energy to maintain organization. And like Dr.Weber said, we would just be a a bunch of useless atoms, if entropy were to be true for us. Quite a contrast to what we are now, isn't it? 

There are two types of energy reactions, endergonic and exergonic. Exergonic energy exchange is spontaneous and releases energy. Delta-G (energy available for work) lower than 0 means that products have less free energy that reactants. Delta-G higher that 0 means that products have more free energy than reactants, meaning they absorbed energy. This is called a endergonic reaction, and it is non-spontaneous. Change in free energy of a reaction determines its spontaneity. 

10/15/2010 (submitted 10/18/2010)

Today we focused on enzymes and how vital they are in body functions. Enzymes are complex proteins that aid reactions, not provide energy for them. Typically, for reactions to occur, a high amount of energy is required to start the process. Because the human body must maintain a optimal temperature at all times, they cannot afford to absorb that much heat. Heat absorbtion would raise body temperatures, denature proteins, and start to kill body cells and prevent them from functioning. To avoid this, the body uses enzymes, which simply bring the reactants close together in a defined area and strain the bonds, lowering the amount of energy required to kick start the process. Now the transition state is achieved faster with a much smaller amount of energy. Smart-thinking! Basic enzyme structure contains an active site, where the reaction occurs. Substrates, or reactants, are what bind to the active sites.

When enzyme activity is graphed, many factors are recorded. V-max is the velocity of a reaction near maximal rate. V-max occurs when the graph reaches a plateau. All enzymes are completely saturated with substrate, thus increasing the substrate concentration does not affect reaction rate. K-m is the measure of substrate concentration at which the reaction reaches half its V-max. K-m more appropriately is the measure of the affinity a substrate has to its activation site. For example, if two enzymes are being tested for the same substrate, the enzyme that reaches K-m with a smaller amount of concentration or reaches V-max first, is the preferred enzyme because those enzymes bind more readily with the substrate. Now, along with enzymes come inhibitors. inhibitors bind to a site on the enzyme to stop it from carrying out further reactions in order to stop over production. The first type of inhibitor is competitive. In this, a small molecule binds directly to the active site, reducing a substrates affinity. It takes a much longer time for the enzyme to reach V-max. With non-competitive inhibitors, a molecule binds at an alternate site on the enzyme, changing its shape, structure, and function. With non-competitive inhibitors, the enzyme never reaches its potential V-max, and the reaction plateaus earlier than it would. 

B.  Useful Materials

1. Enzyme Function and Inhibition - This video gives a quick overview of enzymes with and without inhibitors. It also shows the type of inhibitors that exist and how they affect reactions.

2. This image shows the V-max of three different situations. Without an inhibitor, V-max is achieved almost right away. With a competitive inhibitor (attaches to active site), the V-max is achieved but at a slower rate. With a noncompetitive inhibitor (attaches to allosteric site), the shape of a enzyme is changed and the enzymes potential V-max is never achieved. 

3. The image shows the activation energy of a reaction with and without the use of enzymes. Without an enzyme, the peak is much higher because it takes a lot of energy to bring molecules together and break bonds. Reaction with a enzyme has a much smaller peak. This is because enzymes bring the reactants closer together and strain their bonds. This allows for a smaller investment of energy and the reaction reaches in transition state much faster. This particular reaction is exergonic because the reactants have more energy than the products.

4. Photosystems and Global Effects of Oxygenic Photosynthesis - The world follows the second law of thermodynamics, of constant spontaneous entropy. Organisms, however contradict this law. In plants, Oxygenic photosynthesis is the largest producer of oxygen and organic matter. It is a principle step in sustaining life, thus is high organized. One process of this, Photosystem II, has the capability of creating highly positive redox reactions (endergonic), keeping the reaction organized.This step contradicts the law. Another step, Photosystem I, generates the most negative redox reactions (exergonic) and account for most of the organism entropy. This step follows the law of thermodynamics.

According to my understanding, I guess the body can not always contradict the law because its needs to to switch between spontaneous and non-spontaneous reaction in order to maintain its processes and gradients for reactions. If we completely contradicted the law, we just keep on becoming more and more organized, and every single process in the body would be endergonic, making our body very unstable (maybe reactive?).