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Chapter 6 Blog: An Introduction to Energy, Enzymes, and Metabolism (Marvi)

Page history last edited by Marvi Cruz 13 years, 6 months ago


A.  Daily Blog



In today's lecture, the class went over energy--the ability to promote change or do work. Of course, there are different types of energy: kinetic and potential. Kinetic energy is associated with movement; heat is the total of kinetic energy due to molecular motion while temperature is the average kinetic movement due to molecular motion.  Potential energy is due to the structure or location--for example, chemical bonds have potential energy within its molecular bonds. The types of molecules that have energy include ATP and fats stored in C-H bonds.


Again, we went over the Laws of Thermodynamics: the first how energy is transformed but never destroyed; the second was how disorder must be kept in the universe (or, rather, transformation of energy increases disorder). To relate this to my other studies, I related the laws to how the world is. Assume that energy is a certain culture--for the sake of the relating them to the laws, say the American culture during the 1920s. During this era, change was beginning to occur and transform the American culture from Victorian to more modern. For some Nativists, they believed that the transformation was causing disorder and didn't want it to happen because they didn't want "their" American culture to be destroyed. However, the American culture was not destroyed but instead changed and tweaked, still causing disorder amongst the Nativists. So, it is much like how energy is transformed, never destroyed, and keeps a consistent amount of disorder.


However, humans, themselves, find a way to counteract the second law of thermodynamics, for if we didn't, we wouldn't be anything but atoms (and, in all honesty, I would find that a tad more tolerable than a struggling human life). Energy, though, allows to decrease entropy and maintain a highly ordered system. Entropy, by the way, is a measure of disorder that cannot be harnessed in work. The example that Dr. Weber used that I found understandable was how in a bank account, there is five hundred dollars but only four hundred dollars can be spent.


Near the end of class, we started to discuss endergonic and exergonic reactions. In an endergonic reaction, there is a positive free energy change, not spontaneous and requires an addition of free energy. In an exergonic reaction, however, there is negative free energy (or rather, energy releasing reaction) that is spontaneous.



The discussion kicked off with the topic of enzymes and ribosomes. Enzymes, as learned in lab, lower activation energy but does not turn delta-G from negative to positive.  There are two types of ways to overcome activation energy: large amounts of heat or using enzymes to lower activation energy (therefore a small amount of heat can push reactants to a transition state).


Features of enzymes include an active site, where a reaction takes place and a substrate, a reactant that binds to an active site. An enzyme-substrate complex is whenever reactions are bound to an active site. Next, we talked about enzyme reaction. A saturation is when there is a plateau when nearly all active sites are occupied by a substrate. When my group and I were discussing a few questions, I enjoyed the example Yianni and Philip gave me. If there was a person carrying cans to one place, they could only carry two cans (one for each hand) and that's the rate they go at.


Then, we talked about competitive inhibition as well as noncompetitive inhibition. In competitive inhibition, molecules bind to an active site and ruins the chance for a substrate to bind but can eventually reach its saturation. Noncompetitive inhibition would be much better, on the other hand. This is because the noncompetitive inhibition makes sure that the V-max is never reached by inhibiting an allosteric site and changes the shape.


B.  Useful Materials


Mouse that Shook the World: (10/18/10) So, one of my worst animal related nightmares has come to past: mice become superior to humans. This article talks about a mouse that was injected with an enzyme, PEPCK-C, when it was an embryo. From experiments, it was shown that it can eat twice as much as an ordinary mouse and be less than half the weight of it, run 20 meters per minute for five hours without stopping, breeds three times as much and lives longer than an ordinary mouse.  When I read this article and realized that it was because of this enzyme, I couldn't help but that, "Dang, it's the new Mighty Mouse."



(10/18/10) In this video, it briefly describes the process of enzymes which we discussed in class. The video itself, though brief, is quite the overview of what was talked about in class. For example, it discusses how substrates bind to enzymes on the active site. Then, it mentions that the enzyme changes shape so it can make it so that the substrate (or substrates) are in a better position to undergo a reaction and therefore make a product. When the the product is complete, the enzyme releases the substrate.


Herbicide Atrazine : (10/18/10) In this PubMed article, it discusses the effects and toxicity of the herbicide atrazine on lipid peroxidation and antioxidant enzyme in the freshwater fish, Channa punctatus. Exposed for fifteen days to sublethal concentrations of herbicide, oxidative stress in the liver was evidence that the levels of lipid peroxidation increased. Because the antioxidants responded positively to the concentration amounts of herbicide, it suggests that the use of the antioxidants as potential biomakers of toxicity.


Comments (1)

Derek Weber said

at 3:21 am on Oct 26, 2010

Great job on this chapter Marvi.

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