Podcast
Questions and Answers
What is the primary function of lactate produced during the fermentation process of kimchi?
What is the primary function of lactate produced during the fermentation process of kimchi?
Which enzyme is NOT involved in the metabolism of hexoses?
Which enzyme is NOT involved in the metabolism of hexoses?
What are the primary locations of gluconeogenesis in the body?
What are the primary locations of gluconeogenesis in the body?
Which of the following statements about gluconeogenesis is correct?
Which of the following statements about gluconeogenesis is correct?
Signup and view all the answers
What happens to glucose levels in the body during fasting?
What happens to glucose levels in the body during fasting?
Signup and view all the answers
Which enzyme is involved in converting pyruvate to phosphoenolpyruvate?
Which enzyme is involved in converting pyruvate to phosphoenolpyruvate?
Signup and view all the answers
What is the impact of gluconeogenesis and glycolysis occurring simultaneously?
What is the impact of gluconeogenesis and glycolysis occurring simultaneously?
Signup and view all the answers
Which compound is crucial for regulating glycolysis?
Which compound is crucial for regulating glycolysis?
Signup and view all the answers
Which step of gluconeogenesis is specifically regulated at the fructose bisphosphatase step?
Which step of gluconeogenesis is specifically regulated at the fructose bisphosphatase step?
Signup and view all the answers
What type of reaction do phosphatases perform in gluconeogenesis?
What type of reaction do phosphatases perform in gluconeogenesis?
Signup and view all the answers
Which of the following is a result of alcoholic fermentation?
Which of the following is a result of alcoholic fermentation?
Signup and view all the answers
What is a physiological effect of alcohol consumption?
What is a physiological effect of alcohol consumption?
Signup and view all the answers
What byproduct can methanol cause if not treated with ethanol?
What byproduct can methanol cause if not treated with ethanol?
Signup and view all the answers
Study Notes
Week 8 - Synchronous Lecture: The Fate of Pyruvate and Gluconeogenesis
- Kimchi is a fermented food produced by microorganisms via anaerobic glycolysis. Lactate is a byproduct and acts as a preservative.
Metabolism of Other Hexoses
- Glucose, galactose, and fructose are metabolized differently, but all eventually lead to pyruvate.
- Specific enzymes are involved in processing each sugar; examples include hexokinase, galactokinase, fructokinase, and others.
- Different pathways exist for metabolism within muscle vs. liver cells.
Metabolism of Other Hexoses (More Detail)
- Galactose is converted to G6P through galactokinase then to Glucose-1-P.
- Fructose (muscle) uses hexokinase,
- Fructose (liver) uses fructokinase for breakdown.
Fructose and Obesity
- High-fructose corn syrup consumption has significantly increased in the U.S. in recent years.
- Research suggests a link between high fructose consumption and obesity.
- High-fructose corn syrup is prevalent in many processed foods.
- Fructose is metabolized differently than glucose and is more likely to be stored as fat.
- Bypassing PFK leads to glycerol-3-phosphate (liver) formation, a precursor to triglycerides.
Glycogen Metabolism
- Glycolysis converts glucose into pyruvate, releasing ATP.
- Gluconeogenesis produces glucose from non-carbohydrate sources when glucose levels are low.
- Glycogen is a storage form of glucose.
- Glycogenolysis is the breakdown of glycogen into glucose.
- Glycogenesis is the production of glycogen from glucose.
- Normal blood glucose levels are 80-110 mg/dL.
Gluconeogenesis
- Brain and red blood cells need glucose for fuel.
- Gluconeogenesis occurs primarily in the liver and to a lesser extent in the kidneys during fasting.
- It makes glucose from non-carbohydrate precursors.
- Gluconeogenesis does not simply reverse glycolysis, it requires alternative reactions.
Gluconeogenesis (Location)
- Enzymes for glycolysis and gluconeogenesis are located in the cytosol.
Gluconeogenesis (Problem)
- Some reactions of glycolysis are irreversible.
- Gluconeogenesis needs different reactions to bypass these irreversible steps.
Gluconeogenesis (Enzymes)
- Key enzymes important in gluconeogenesis include pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose bisphosphatase, and glucose-6-phosphatase. These enzymes catalyze reactions to circumvent the irreversible steps.
Glucose-6-Phosphatase and Fructose Bisphosphatase
- These are crucial enzymes in gluconeogenesis. Removal of phosphate groups is needed.
- They use hydrolysis to bypass irreversible steps in glycolysis.
Pyruvate to Phosphoenolpyruvate
- Pyruvate is converted to phosphoenolpyruvate through pyruvate carboxylase and phosphoenolpyruvate carboxykinase, a process requiring energy.
- Pyruvate can be made from lactate (homolactic fermentation) and breakdown of amino acids.
Glycolysis vs. Gluconeogenesis
- Glycolysis and gluconeogenesis are opposing processes.
- Simultaneous operation would be wasteful. Regulation is required to ensure pathways operate in a complementary fashion, rather than futile cycles.
- Glycolysis "ON" during sufficient glucose levels, gluconeogenesis would be "OFF." The Opposite is also true.
PDC (Pyruvate Dehydrogenase Complex) Control
- PDC activity is regulated in different ways. Product inhibition is one mechanism.
- Covalent modification, specifically phosphorylation, is another key regulatory step to control E1.
PDC Cofactors/Prosthetic Groups
- Several cofactors, such as thiamine pyrophosphate (TPP), lipoic acid, coenzyme A (CoA), FAD, and NAD+, are necessary for the PDC to function.
PDC Reactions
- The PDC catalyzes a series of reactions that convert pyruvate to acetyl-CoA, a preparatory step for the citric acid cycle; this produces CO2.
Lipoamide and Acetyl-CoA
- Lipoamide is a crucial cofactor in the PDC and it carries the acetyl group to Coenzyme A in the reaction
PDC Control (Summary)
- Levels of reaction products (like acetyl-CoA) and changes in the activity of individual enzymes within the complex control PDC activity.
- In the other hand, phosphorylation, and dephosphorylation of the E1 enzyme acts as a major switch to regulate the PDC.
Activity W8L1 & W8L2 Questions
- Metformin reduces phosphoenolpyruvate carboxykinase expression and thus likely decreases blood sugar levels.
- An increase in acetyl-CoA levels would increase PDC activity. An increase in calcium levels would lead to increased PDC activity.
Activity W8L3 Question
- Decreased activity of pyruvate carboxylase is least likely to decrease levels of cytosolic acetyl-CoA, because pyruvate carboxylase is required to make oxaloacetate from Pyruvate, which is required later during gluconeogenesis.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the metabolic pathways of different hexoses, including glucose, galactose, and fructose, and their conversion to pyruvate. It also discusses the implications of high-fructose corn syrup on obesity and the role of various enzymes in metabolism. Test your understanding of these crucial biochemistry concepts.
