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Chapter 7 Blog: Cellular Respiration, Fermentation, and Secondary Metabolism (Siddarth)

Page history last edited by Siddarth Santhebennur 12 years, 11 months ago

In the first section of this page, you will write a daily summary of that day's class.  For example in  your chapter 2 blog, your first entry should be titled 9/3/10.  You should then write a one or two paragraph summary of that day's lecture, outlining the major points.  In the second section, you are required to add two items (link to a website, video, animation, student-created slide show, student-created PowerPoint presentation) and one journal article pertaining to a topic in this chapter.  A one-paragraph summary must accompany each item describing the main idea and how it applies to the lecture topic.  Please see the PBWorks help guide for assistance embedding video and other items directly in the page.  I will also produce a how-to video on using tables to wrap text around items and other useful tips.  Please see the syllabus for organization and grading details.

 

A.  Daily Blog

October 20,2010: Today we started Chapter 7 and cellular respiration. We started off by talking about the 2 different ways that we know of to make ATP in a cell which are: 1. Substrate Phosphorylation and 2. Chemiosmosis. Out of these two, Chemiosmosis produces more ATP (28-32) unlike Substrate Phosphorylation (4). We then brought back the Laws of Thermodynamics. We mainly focused on the 1st Law which states that energy can never be produced or destroyed, only transferred. So we then began list molecules that had energy stored within them. These molecules were ones that we had already heard of such as: Carbohydrates, Fats, Proteins and ATP. Energy can also be found in environments such as: gradients. In these gradients, there is potential energy that is being transferred when driven across the membrane. We then looked at glucose as an example of a substance that is used to get energy. If it went through a direct exergonic reaction, it would produce 686 kcal/mol which can't be used. This will end up becoming heat which is harmful for the cell's environment. This is were "steps" come in order to reduce the amount of heat given off. The steps that I am referring to is: Glycolysis, acetyl CoA, and Citric Acid Cycle. This is a 20 step process in order to prevent all that heat to be given off. We then moved onto what Energy Intermediates were. These are molecules that help in transfer of energy are generally temporary for uphill (endergonic) reactions. An example of an Energy Intermediate's are: ATP and NAD+. 

     We then started talking about the four different metabolic pathways that we use to transfer energy. These are: Glycolysis, Breakdown of Pyruvate to an acetyl group, Citric Acid Cycle and Oxidation Phosphorylation. This is when the real details started to come into play. We discussed the different steps of Glycolysis and how energy is being transferred across a molecule. To carry out this process, we need ENZYMES! There are specific enzymes needed at certain stages of glycolysis such as: hexokinase, isomerase, and phosphofructose kinase. When I saw the last one I was like...wow didn't see that coming. We used glucose as the molecule being broken down just as an example of what could happen to a molecule being broken down in these stages. We discussed how the first enzyme helped bring a phosphate from ATP to the glucose molecule to make it glucose-6-phosphate. (which is transferring energy since ATP is being inputed). Then the second enzyme helps slightly change the structure of the molecule to make it fructose-6-phosphate. Then the enzyme PFK is used to to form fructose-1,6-bisphosphate which is then ready for cleavage. During cleavage, the fructose-1,6-bisphosphate is broken down to 2 G3P (Glyceraldehyde 3 Phosphate). Towards the end of the class we briefly discussed how NAD+ acts as a intermediate in order to prevent heat loss. I learned a lot from this lecture...much more than I expected!

 

October 22, 2010: Today in class, we finished up the process of cellular respiration inside of cells. We picked up from where we discussed what the "Fate of Pyruvate" was going to be. So basically the 2 pyruvate molecules formed from glycolysis are then broken down in order to form an Acetyl group. This Acetyl group is attained by the removal of electrons thanks to the help of the enzyme dehydrogenase. This enzyme is going to be talked about a whole lot in this blog entry. Once broken down, CoA is attached to each pyruvate molecule. There are some products that are released during this process which is good, old-fashoined CO2. So the removal of the CO2 in this process is known as decarboxlyation, It kinda has the meaning in the word itself. CO2 is just a carboxyl group, so the removal of this carboxyl group results in decarboxylation. Then the citric acid kicks into play! During the citric acid cycle, we saw a repetition of the usage of the enzyme dehydrogenase as well as the enzyme synthase. The removal of electrons with dehydrogenase helped in the energy transferring to the energy intermediates: FADH and NADH. It also assists in the production of 2 more ATP molecules. So Dr. Weber took us step by step and pointed out how the same process was going on in the citric acid cycle. The only difference I noticed was the name of the enzyme which could possibly be the actions of the enzyme isomerase. The point that Dr. Weber got in our heads was that the citric acid cycle is nothing more than a repetition of steps. Isn't that neat? 

 

October 27, 2010: Today in class, we spent the first half hour going over what happened during glycolysis and the citric acid cycle. We talked about the energy intermediates used in this process as well as where the energy is transferred. We then started to discuss what the electron transport chain. This concept seemed to make a lot of sense especially when we started to talk about the errors that could occur. What I understood from this lecture was that the electron transport chain was where the main bulk of ATP is made during the process of cellular respiration. About 30-34 ATP molecules are formed just from the oxidation of NADH. I find it amazing how 1 molecule can create so many energy intermediates to store this energy. So with the release of an H+ ion and 2e-, these are passed onto other protein complexes that just happen to be transport proteins for H+ ions in the matrix which is an example of ACTIVE TRANSPORT. When there the electrons have finally reached the end of the chain, they are then released in order for an Oxygen molecule to attach to them and tun into H2O. When there is an influx amount of H+ ions on the outside of the inner membrane, a protein transporter known as ATP synthase. This brings in H+ ions from high to low concentrations which is an example of facilitated diffusion. Towards the end of class we talked about uncoupling proteins are and how they are related to weight loss, but could end up in death....we would not want that happening would we?

 

October 29, 2010: For the first half hour, we discussed what occurs to a cell during the absence of O2. We concluded that an enormous amount of NADH would get backed up and would not be able to oxidize glucose or any other molecules during the process of cellular respiration. We then started to discuss how glycolysis is favored in cancer cells rather than oxidative phosphorylation. Since the cancer cells do not have that much Oxygen and genetic and environmental factors come into play, cancer cells look upon glycolysis in order to get energy. We then started to get into the discussion of Fermentation and Anaerobic respiration. Fermentation does occur within our body, however Anaerobic generally occurs in other cells such as bacteria. Both of these share 1 thing in common. They have no oxygen presence during this process. They both have different final electron acceptors in their cycles and produce energy such as heat. Fermentation can be found to occur in our muscle cells as well as other cells in our body such as liver cells. 

 

B.  Useful Materials

 

 Useful Video  Description 

Cellular Respiration Overview Animation with Glycolysis, Krebs, and ETC

 


 
This is a nice video which goes over all the energy transfer that occur during the process of cellular respiration. It goes over it in detail of how NADH is formed as well as ATP and FADH. 

 


 

Useful Link   Website   Description
Cellular Respiration Animation  http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/oxidative/oxidativephosphorylation.html  This is a really cool link which is a walk through animation of Cellular Respiration. It comes with questions along the way to help quiz you on what you learned. 

 

 

 

Useful Article  Website  Description 

Choosing between glycolysis and oxidative phosphorylation: A tumor's dilemma?

 
http://www.ncbi.nlm.nih.gov/pubmed/20955683  This is a very interesting article that discusses on what kind of energy source is most efficient for the rapid growth of tumor cells. It discusses how tumor cells process so much energy and use it through oxidative phosphorylation. 

 

 

 

 

 

Comments (1)

Derek Weber said

at 3:02 am on Oct 26, 2010

Great job on your posts Siddarth!!!

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