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

Page history last edited by Erica Choi 13 years, 7 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




In this discussion we learned about the two ways to make ATP, through substrate-level phosphorylation(--->4 ATP) and chemiosmosis (H+ gradient is used to store energy-->28-32 ATP).  ATP, carbs, fats, proteins, bonds, and concentration gradients are used to store energy. Redox reactions are the movement of electrons to more electronegative atoms.  When this happens NADH is produced.  Cellular respiration makes ATP and NADH, it's a process that uses oxygen because oxygen takes electrons from the other molecules.  During Glucose metabolism, glucose goes through a three step process: glycolysis, acetyl CoA production, and the Citric Acid Cycle.  During glycolysis the first stage is the energy investment phase, the enzyme kinase transfers phosphates in order to instill a lot of energy in the molecule to make it unstable: hexokinase-transfers phosphates to the 6 sugar, isomerase-forms fructose 6-phosphate from glucose 6-phosphate, phsophocructokinase- describes substrate, or catalyzes the third step in glycolysis which is the most important regulation step.  The next step is cleavage, or the step that breaks the one molecule down into two molecules: glyceraldehyde 3 phosphate is formed which is very unstable, and 60% is lost as heat.  Then comes the oxidizing stage, and NAD+ forms NADH when G3P is oxidized, exergonic, to 1;3-BPG.  This creates heat, but NAD++2e-+H+ which is eventually reduced to NADH, the enzyme dehydronase which catalyzes redox reactions.  




Glycolysis yields two pyruvates, and there are two main routes.  If there is oxygen it goes to the mitochondria, and eventually it goes through acetyl CoA production and the citric acid cycle.  If there is no oxygen it can either go through the cytoplasm, where fermentation takes place, or mitochondria, where anaerobic respiration takes place.  We then discussed the citric acid cycle and how it starts off with oxaloacetate, and ends with oxaloacetate. At the end of teh cycle it yields 6 NADH, 2 ATPs, 2 FADH2, and 2 CO2.   




In the beginning of class we reviewed the steps of glycolysis, we then moved on to the process of oxidative phosphorylation.  In the process NADH is oxidized to NAD+, and the hydrogen ion then attaches to O2 and reduces to become H2O.  This process occurs via the electron transport chain so that not too much of the energy is lost as heat. The electron transport chain is in the matrix of the mitochondria, and the cristae allows for more surface area therefore more places where ATP can be produced. It is an exergonic process where NADH transfers its electrons to NADH dehydrogenase, and then the active transport of H+ occurs while the electrons are passed down the chain to cytochrome b-c, to cytochrome oxidase, to O2, and eventually H2O is formed at the end of the electron transport chain.  H+ ions are pumped to the intermembrane space to create a concentration gradient via active transport, this is used to store energy.  ATP is made from this when ATP synthase turns and transfers H+ ions stored as energy in the H+ gradient, into ATP via facilitated diffusion from the intermembrane space to the matrix.  Towards the end of class we began to discuss the roles of uncoupled proteins and how they decrease ATP production by tricking the body into using catabolic conditions, and this is when fat is used as energy. 




We started off the class reviewing what would happen if oxygen became limiting: the electron transport chain would have nothing to accept the electrons at the end, there would be an increase in NADH and a decrease in NAD+, the citric acid cycle, pyruvate oxidation, and glycolysis production would all go down and glucose, fats, and proteins would all be in abundance, while the ATP level decreases.  The oxidant is incompletely reduced in ETC in O2-species.  Exposure to oxidant may cause damage to your cells.  Gang Green is a disease in which there is a lack of O2, and this can be killed by exposing the area to pure O2 because this would kill the cells causing gang green since they don't need O2.  Fermentation is when NADH donates to pyruvate instead of oxygen to form lactic acid and ethanol.  Although no energy is produced, it forms heat which just releases energy in NADH.  Lactic acid build up causes fatigue and soreness because it can't deliver oxygen fast enough to the cells.  Organisms that don't use O2 form energy by using Anaerobic respiration.  This process uses other acceptors like nitrate reductase instead of cytochrome, and it actually produces a better yield. 

B.  Useful Materials


  This animation helps demonstrate, or provide a visual, of what happens during glycolysis. It introduces glucose getting oxidized to glyceraldhyde phosphate as it briefly gives an overview of the whole cycle. 
  This video breaks down the citric acid cycle: pyruvate is broken down to Acetyl CoA which then enters the cycle, which attaches to oxaloacetate.  Citrate is formed, and a series of carboxylations and transformations take place that are not specified in this video, but can be found in our textbook.  ATP is produced via substrate-level phosphorylation.  The oxaloacetate is then regenerated and the cycle starts again.  This process yields 2 ATP, 6 NADH, and 2 FADH2 when 2 pyruvates are used.   
Cancer Cells and glycolysis!  Cancer cells mostly use glycolysis and produce energy in the form of ATP via oxidative phosphorylation in aerobic glycolysis.   According to this article, it seems like cancer cells have not always used glycolysis because it says that it is likely that mitochondrial damage to the electron transport chain and the increased production of reactive oxygen-using species as a result could be the reason why.  This team studied transcription factor Ets-1 in the regulation of mitochondrial function and metabolism.  It was shown numerous times using a certain vector in the ovarian cancer cell line, and microarray analysis of the effects of Ets-1 show that it regulates key enzymes involed in glycolysis, associated feeder pathways, fatty acid metabolism, and antioxidant defense.  It also has an effect on the regulation of the citric acid cycle, electron transport chain, and mitochondrial proteins.  This means that when Ets-1 is over expresed, that it could cause decreased oxygen use.  It can also cause an increase of sensitivity to glycolytic inhibitors, or growth inhibition in an environment that does that contain much glucose.  



Comments (2)

Derek Weber said

at 3:19 am on Oct 26, 2010

No 10/20 and 10/22 updates.

Derek Weber said

at 2:19 am on Nov 23, 2010

Great job on the summary of the journal article. You can make the table wider by right clicking an selecting properties. You can make it % width of the page.

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