Glycolysis

• What is the main outcome of glycolysis?

  Convert glucose to pyruvate
• Why is glucose metabolism important?

  It maintains energy levels in the body
• What are the two mechanisms for glucose entry into cells?

  Facilitated diffusion and Na+-dependent co-transport
• How does glucose enter most cell types?

  By facilitated diffusion mediated by GLUT proteins
• What is the role of hexokinase in glucose metabolism?

  Phosphorylates glucose to glucose-6-phosphate
• What happens to glucose once it enters the cell?

  It is phosphorylated to glucose-6-phosphate
• How do hexokinase and glucokinase differ in function?

  Hexokinase has a low Km; glucokinase has a high Km
• What is the significance of glucokinase in the pancreas?

  It helps β-cells sense rising glucose levels
• What is the end product of glycolysis?

  Pyruvate
• What is the role of phosphofructokinase 1 (PFK1) in glycolysis?

  It is the rate-limiting step of glycolysis
• How is PFK1 regulated?

  Inhibited by ATP and activated by fructose-2,6-bisphosphate
• What happens to pyruvate under anaerobic conditions?

  It is converted to lactate
• What is the main difference between aerobic and anaerobic metabolism?

  Aerobic metabolism produces CO2 and H2O
• What are the steps of glycolysis?

  1. Glucose is phosphorylated to glucose-6-phosphate
  2. Conversion of glucose-6-phosphate to fructose-6-phosphate
  3. Phosphorylation to fructose-1,6-bisphosphate
  4. Cleavage into two 3-C molecules
  5. Conversion of 3-C molecules to pyruvate
• What are the alternative metabolic uses of pyruvate?

  • Converted to acetyl-CoA for TCA cycle
  • Converted to lactate under anaerobic conditions
  • Used in gluconeogenesis
  • Precursor for amino acid synthesis
• What are the regulatory mechanisms of glycolysis?

  • Allosteric regulation by ATP and fructose-2,6-bisphosphate
  • Hormonal regulation by insulin and glucagon
  • Feedback inhibition by glucose-6-phosphate
• What are the consequences of lactic acid accumulation?

  • Muscle cramps during vigorous exercise
  • Lactic acidosis in circulatory collapse
  • Potentially fatal conditions if untreated
• How does aerobic metabolism differ from anaerobic metabolism in terms of efficiency?

  • Aerobic metabolism is more efficient
  • Allows complete oxidation to CO2 and H2O
  • Anaerobic metabolism results in less ATP production
• What enzyme is involved in the control of blood glucose concentration?

  Phosphofructokinase 1
• What accumulates under anaerobic conditions?

  Lactic acid
• What promotes anaerobic glycolysis?

  Lack of oxygen
• What is the result of anaerobic glycolysis?

  Lactic acid synthesis from pyruvate
• What happens to ATP synthesis during anaerobic conditions?

  It decreases
• What condition can lactic acid accumulation lead to?

  Lactic acidosis
• What can cause elevated plasma levels of lactic acid?

  Circulatory collapse and shock
• What does MI stand for?

  Myocardial infarction
• What does PE stand for?

  Pulmonary embolism
• How much ATP is produced from anaerobic glycolysis?

  2 ATP
• What enzyme converts pyruvate to lactate?

  Lactate dehydrogenase
• What does the conversion of pyruvate to lactate consume?

  NADH
• Why is aerobic metabolism more efficient than anaerobic metabolism?

  It allows complete oxidation of fuel molecules
• What are the end products of aerobic metabolism of glucose?

  CO2 and H2O
• What is the ATP yield from aerobic metabolism compared to anaerobic metabolism?

  Much higher
• What are the two ways ATP is produced?

  • Directly: substrate-level phosphorylation
  • Indirectly: oxidative phosphorylation
• What is the reaction that generates ATP from NADH?

  NADH + H+ → 3 ATP
• What is the reaction that generates ATP from FADH2?

  FADH2 → 2 ATP
• What are the metabolic pathways for glucose in anaerobic and aerobic metabolism?

  • Anaerobic: Glucose → Glycolysis → Pyruvate → Lactate
  • Aerobic: Glucose → Glycolysis → Pyruvate → TCA Cycle & Oxidative Phosphorylation → CO2 + H2O
• What is the conversion of pyruvate to Acetyl-CoA catalyzed by?

  Pyruvate Dehydrogenase complex
• What can Acetyl-CoA enter after its formation?

  The TCA Cycle
• What is the metabolic fate of pyruvate in anaerobic conditions?

  Conversion to lactate