GLYCOLYSIS

• Glycolysis


  The process of oxidizing a molecule called glucose
• Glucose


  A six carbon monosaccharide (sugar) obtained from the diet
• Cell membrane


  Glucose cannot passively diffuse through, it requires specialized transporters called GLUT transporters
• GLUT transporters


  • GLUT1
  • GLUT2
  • GLUT3
  • GLUT4
• GLUT1


  Found in red blood cells, fetus, and blood-brain barrier
• GLUT2


  Found in kidney, liver, and pancreas
• GLUT3


  Found in placenta, neurons, and kidney
• GLUT4


  Insulin-dependent, found in muscle and adipose tissue
• Glucose entry into cell

  1. Transported by GLUT transporter

  2. Phosphorylated by hexokinase or glucokinase to glucose-6-phosphate
• Hexokinase


  Enzyme that phosphorylates glucose in most tissues
• Glucokinase


  Enzyme that phosphorylates glucose specifically in the liver
• Conversion of glucose-6-phosphate to fructose-6-phosphate


  Catalysed by phosphohexose isomerase
• Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate

  Catalysed by phosphofructokinase-1 (PFK-1), uses ATP
• Fructose-1,6-bisphosphate


  Six carbon sugar with two phosphate groups
• Cleavage of fructose-1,6-bisphosphate


  Catalysed by aldolase, produces dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GA3P)
• Conversion of DHAP to GA3P

  Catalysed by triose phosphate isomerase
• 1,3-bisphosphoglycerate


  Three carbon sugar with two phosphate groups
• Carbon


  • 1
  • 2
  • 3
• The phosphate is on the third carbon
• There are two phosphates
• 1,3-bisphosphoglycerate


  A three carbon glycerate molecule with phosphates on the 1st and 3rd carbons
• Glyceraldehyde 3-phosphate dehydrogenase


  An enzyme that catalyses a key step in glycolysis
• Glyceraldehyde 3-phosphate dehydrogenase catalysis

  1. Substrate binding

  2. NAD+ reduction to NADH

  3. Inorganic phosphate addition

  4. Product release
• 1. phosphoglycerate


  A three carbon molecule with a phosphate on the 3rd carbon
• Phosphoglycerate kinase


  An enzyme that catalyses the conversion of 3-phosphoglycerate to 2-phosphoglycerate, producing ATP
• 1. phosphoglycerate


  A three carbon molecule with a phosphate on the 2nd carbon
• Enolase


  An enzyme that catalyses the conversion of 2-phosphoglycerate to phosphoenolpyruvate
• Phosphoenolpyruvate (PEP)


  A three carbon molecule with a phosphate in an enol structure
• Pyruvate kinase


  An enzyme that catalyses the conversion of phosphoenolpyruvate to pyruvate, producing ATP
• Glycolysis produces 2 ATP, 2 NADH, and 2 pyruvate molecules
• Anaerobic conditions


  Conditions with little to no oxygen present
• Aerobic conditions


  Conditions with plentiful oxygen present
• Pyruvate conversion under anaerobic conditions

  1. NADH reduces pyruvate to lactate

  2. Catalysed by lactate dehydrogenase
• High lactate dehydrogenase levels can indicate conditions with limited oxygen supply, such as myocardial infarction or ischemia
• Glycolysis summary


  • Occurs in cytoplasm
  • Starts with glucose
  • Produces 2 ATP, 2 NADH, 2 pyruvate
  • Anaerobic process can produce lactate