Updated by Amy Medlock (Fall 2017). Carbohydrate Metabolism I End of Module Assignment Honor Statement: This assignment adheres to the standards of UGA’s Culture of Honesty policy. The answers to these questions are my own words and all external sources (besides your textbook, group, professor and PLAs) have been cited. (You do not need to use proper citation formatting, just copy and paste the link.) The breakdown and building of carbohydrates by an organism (e.g., human) involves a series of chemical reactions called metabolic pathways. The directionality of each reaction in a pathway depends on the free energy and relative concentrations of reactants and products available. The observable “flux” of a pathway is the net result of forward and reverse processes. Enzymes control rates of forward and reverse reactions in a pathway, and their activity is highly regulated. Enzyme-mediated regulatory mechanisms allow pathways to be sensitive and responsive to the needs of the organism. In metabolic pathways, a favorable process is often used to drive a less favorable process. 1. Identify components of the insulin signaling pathway and explain how the pathway results in a change in blood glucose levels. 2. Summarize the answers to the following questions for any given reaction in glycolysis: a. What is the G for the reaction under typical physiological conditions? b. Is the reaction readily reversible under typical physiological conditions? c. What enzyme catalyzes the reaction and what type of reaction is occurring? d. Is the enzyme regulated; if so, how? 3. Apply your knowledge of the reactions in glycolysis to answer the questions above about a chemical reaction that is new to you (i.e., that we’ve not considered in class). 4. Explain how coupling facilitates thermodynamically unfavorable reactions. For example, how do ATP hydrolysis, oxidation, and decarboxylation drive less favorable reactions? 5. Understand the role of the thioester intermediate in the redox reaction in glycolysis. 6. Describe substrate-level phosphorylation and explain why 1,3-bisphosphoglycerate and phosphoenolpyruvate are substrates for substrate-level phosphorylation. 7. Given the pathways of glycolysis and gluconeogenesis, identify which reactions are most energetically favorable in one pathway under typical physiological conditions, and thus must be bypassed in the opposing pathway. 8. Given the pathways of glycolysis and gluconeogenesis, identify regulatory steps, regulatory molecules, and whether the molecules are activators or inhibitors, especially molecules such as AMP, ATP, acetyl-CoA, citrate, and fructose-2,6-bisphosphate. 9. Describe how insulin and glucagon regulate glucose metabolism in the liver, including how glucagon signals the liver to phosphorylate PFK2-FBPase2. In Module 1 and 2, you learned about Insulin and the Insulin Degrading Enzyme. Let’s look at some other aspects of the Insulin Signaling Pathway. Insulin binds to the insulin receptor (1); Receptor is activated, causing a conformation change known as dimerization (the coming together of two insulin receptors). Receptor adds a phosphate to amino acids (tyrosines) on the tail of the other insulin receptor in the pair (2). Signal transduction proteins interact with phosphate group (3). Interaction of the phosphate groups with all of the different signaling proteins occurs simultaneously, but each pathway will be discussed individually. Signaling proteins and pathways will cause the short-term and long-term changes in response to the increased glucose in the blood stream. One major short-term change is the fusion of vesicles containing glucose transporter (GLUT4) to the cell membrane (4). Once these transporters are part of the cell surface, glucose is transported into the cell (5). Introduction to Biochemistry and Molecular Biology End of module assignment BCMB 3100E Summer 2022 Take-Home Point Learning Objectives Introduction: Insulin Signaling and Type I DiabetesLong-term cellular changes are caused by changes in gene transcription that result in specific proteins being made or not made. These pathways utilize many different signaling patterns, such as the direct activation of a transcription factor (T.F.) (6), the release of second messenger (7), and the activation of a kinase cascade (8). All of these signaling pathways can result in the activation of transcription factors and their movement to the nucleus to activate transcription (9). Image credit: Kristy J. Wilson A 12-year-old girl is brought to the ER by her parents because she is vomiting and very drowsy. History revealed that within the last 2 weeks following a fever and “cold-like” symptoms, she experienced increased urination and thirst. Upon examination in the ER she is dehydrated with cold, dry skin. She is breathing in a deep and labored manner (Kussmaul respiration) and her breath has a fruity odor. Blood glucose levels are 792 mg/dL (normal 70 to 110 mg/dL). Based on this girl’s personal history andsymptoms you suspect that she has Type I diabetes mellitus which results from a lack of insulin and is suffering from ketoacidosis. 1. How did this patient’s lack of insulin result in an elevated blood glucose level? Be specific as to what aspect(s) of the insulin signaling pathway shown above are directly involved. The patient’s lack of insulin resulted in an elevated blood glucose level because insulin is required to ultimately facilitate glucose transport from the blood into the cell. Specifically, insulin binds to the insulin receptor on the cell membrane causing a conformational change bringing together two insulin receptors (i.e. dimerization), The activated receptor then allows phosphorylation of tyrosine amino acids on the tail end of the other insulin receptor. Various signal transduction proteins interact with the phosphate group leading to short term and long term changes in response to the elevated blood glucose. One specific change is allowing vesicles containing glucose transporter (GLUT4) to fuse to the cell membrane. Once the glucose transporter fuses to the cell membrane it allows glucose to be transported from the blood to inside the cell where it can be broken down. Without insulin, these steps do not occur and blood glucose levels rise. 2. The insulin signaling pathway affects the regulation of glycolysis. View the table below, which details all ten