Biochemistry 1 - Carbohydrate metabolism I

• Glycolysis

  • 2 ATP in and 4 ATP out = net gain of 2 ATP
  • Hexokinase and phosphofructokinase both use ATP ( 2 ATP in) in energy investment stage
  • Phosphoglycerate kinase and Pyruvate kinase each produce 1 ATP molecule and this happens twice to produce 2 molecules of pyruvate, so energy generation produces 4 ATP
  • Red blood cell glucose metabolism is entirely anaerobic
• NAD+ recovery

  Aerobic conditions

  • Pyruvate is imported into the mitochondria
  • Converted to Acetyl CoA for TCA cycle
  • Electron transport activated
  • NADH oxidised to NAD+ by the electron transport chain

  Anaerobic conditions

  • NADH not oxidised by the electron transport chain
  • NADH builds-up
  • Pyruvate reduced by NADH to lactate by lactate dehydrogenase(LDH)
  • NAD+ used for glycolysis - Common in muscle cells
• The Cori cycle

  1. Glycolysis in the muscles converts Glucose to lactate(Anaerobic)
  2. Lactate is transported to the liver through the blood
  3. Gluconeogenesis in the liver reforms glucose from lactate
  4. Glucose is transported back to the muscles through the blood
• Lactic Acidosis

  • lactic acid (lactate) build up in the bloodstream
  • symptoms (Nausea, vomiting weakness)
  • Caused by decreased lactate clearance or increase formation or decrease O2 delivery to tissue
• Pentose shunt

  • Oxidative Phase Dependent on the availability of NADP+Nonoxidative PhaseDependent on the availability of substratesExamples
• Pentose Shunt

  • Oxidative PhaseDependent on the availability of NADP+Nonoxidative PhaseDependent on the availability of substratesExamples