Wgu Est1 Task 4

Task 4
Christopher Mann
Student ID: 000458585
June 5, 2015

Enzymes are special proteins that carry out chemical reactions, also known as catalysts. Two important features that make all enzymes catalysts are their ability to bind to a substrate. A substrate is anything that needs to be changed into something else. The second important feature is that it works to lower the activation energy without being used or changed in the reaction (Hudon-Miller, 2012.
The breakdown of fructose in the liver starts off with two steps unique to fructose itself, prior to entering glycolysis. Fructose, a substrate, is broken down into the product, fructose-1-phophate, by the enzyme, fructokinase. The second step in
the breakdown of glucose is when the product, fructose-1-phosphate is converted by the enzyme, aldolase B, into the two products, DHAP and glyceraldehyde. These two products are now capable of entering the glycolysis pathway (Hudon-Miller, 2012).

During fructose metabolism, fructose is transported into the liver cell and phosphorylated into fructokinase using ATP, which adds a phosphate to the substrate.
Fructose-1-phosphate, or F-1-P, is the specific substrate acted on by the enzyme, aldolase B. Aldolase B takes F-1-P and makes the products, DHAP and Glyceraldehyde. These products are immediates in glycolysis to make fatty acids or ATP or it can go through gluconeogenesis to make glycogen (Sanders,
2013).
Hereditary fructose intolerance, or HFI, is when there is deficiency in the enzyme, aldolase B.
Aldolase B, can no longer take its substrate, F-1-P, and turn it into the products, DHAP and Glyceraldehyde. During HFI, fructose is still being phosphorylated by fructokinase, leading to a build up of F-1-P, and will no longer being used for glycolysis or gluconeogenesis. The continued use of phosphorous leads to the depletion of the free phosphate pool in the cells. The electron transport chain requires phosphate to make ATP. With the low amounts of free phosphate available, ATP production slows. Essentially, fructose is no longer being used as energy by the liver cells. Liver cells are now low on energy leading to liver damage and eventually liver failure. Fructose-1-phosphate produces the symptoms of HFI. It normally acts a signal in high blood sugar instructing the glucokinase to stay in the cytoplasm, so it does not go into the nucleus. When blood sugar is low, and F-1-P builds up, it signals the glucokinse to stay in the cytoplasm leading to a glycogenolysis and gluconeogenesis slowing down. When low blood sugar occurs, the liver cannot release glucose into the blood to help stabilize it, this is known as hypoglycemia. Many symptoms that are involved with hereditary fructose intolerance have to do with hypoglycemia, such as shakiness, headaches, and irritability, in addition to phosphate related liver issues (Sanders,
2013).
Hypothetically, if the Cori cycle were to occur and remain within a single muscle cell there would be two ATP molecules produced by turning glucose into lactate and six ATP molecules to turn lactate back into glucose with a net loss of four ATP per cycle. If the glucose were resynthesized at the cost of ATP and GTP hydrolysis, it would form a futile cycle, until cell death (Concepts in Biochemistry, n.d.).

The citric acid cycle acts as a factory line of workers, each having a specific role. If there was a hypothetical defect or break in the cycle, and citrate synthase, for example, was not working, the cycles product, citrate, and the side-product, CoA, would not be made. If citrate is not made, the next enzyme, aconitase, would be unable to do its job and the next enzyme cannot do its job, and the Citric Acid cycle would not continue. If CoA isn’t made, then another Acetyl-CoA cannot also be made. Due to this defect, the citric acid cycle stops and is unable to produce the appropriate amounts of GTP, NADH, and FADH2. The electron transport chain now has no access to the NADH and FADH2 due to the defect and is unable to create ATP (Hudon-Miller, 2012.)
The coenzyme Q10 or CoQ10 is located in the mitochondria and is a part of the electron transport chain. There are four complexes in the electron transport chain. CoQ10 accepts electrons from complex 1 and complex 2 and transfers them to complex 3. CoQ10 is how electrons get transferred from NADH and FADH2 to complex 3 via complexes 1 and 2. Every time electrons are getting transferred from each complex, it gives off energy. This energy allows complexes 1, 3, and 4 to pump hydrogen ions into the intermembrane space. ATP synthase allows the hydrogen ions in a careful and controlled way back into the matrix. The cell is able to harness the increased amount of energy from the hydrogen ions to take ADP and phosphate and form ATP (Sanders, 2013).
Oxidative phosphorylation is the process in which ATP is made from ADP and phosphate that is propelled by oxidation inside the matrix of the mitochondria. ATP synthase is the primary role in oxidative phosphorylation because of its ability to make ATP from the movement of hydrogen ions down a concentration gradient called chemiosmosis. Phosphate and ADP will then bind with the enzyme, ATP synthase, creating the open channel. Protons quickly come rushing in releasing energy. That energy is now used to join the ADP and phosphate, leading to form ATP (Wolfe, 2000).
References

Concepts in Biochemistry - Interactive Animations. (n.d.). Retrieved June 5, 2015, from http://www.wiley.com/college/boyer/0470003790/animations/cori_cycle/cori_cyl e.htm
Hudon-Miller, S. (2012). Citric acid cycle. Retrieved from https://www.youtube.com/watch?v=Wt5nYED2GJs&feature=youtu.be
Hudon-Miller, S. (2012) Enzymes and fructose breakdown. Retrieved from htps://wgu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=c99ccc40-4cf5- 4e53-b8b1-ccbb100a65c2
Sanders, J. (2013). The centrality of the citric acid cycle. Retrieved from https://wgu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=5f56ada4-2229-4 f96-9770-21dc2738c98e
Sanders, J. (2013). Hereditary fructose intolerance. Retrieved from https://wgu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=4b4de18d-60f5- 4866-a77c-b673ce51aab6 Sanders, J. (2013). Role of aldolase b. Retrieved from https://wgu.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=ce81226c-d293- 4232-997e-fb2957530367
Shmoop Editorial Team. (2008, November 11). Enzymes in Detail - Shmoop Biology. Retrieved June 5, 2015, from http://www.shmoop.com/energy-flow- enzymes/enzymes.html
Wolfe, G. (2000). Thinkwell Biochemistry-section 4.4.2. Oxidative Phosphorylation. etrieved from http://wgu.thinkwell.com/students/getResources.cfm?levelFourID=5869690&leve ThreeID=1820596&levelTwoID=350662&mode=browse