Biochemistry · MU Sofia

19. Glycolysis…

Covers glycolysis as the first stage of glucose breakdown, its importance as a near-universal anaerobic route to ATP, and the ten enzyme-catalysed steps from glucose to pyruvate, shown in a step-by-step list with enzymes and cofactors. It then compares energy yield in aerobic and anaerobic conditions, tissue differences in glycolytic activity, and the fate of NADH, lactate and pyruvate, with the malate-aspartate and glycerophosphate shuttles. It closes with the Pasteur effect, links to the citric acid cycle, lactic acidosis, pyruvate kinase deficiency, and a short multiple-choice quiz with answers.

Inside: 14 sections · 6 labelled pictures · 10 flashcards · 4 min

Topic 19 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 14 sections, about 579 words (4 min of reading), with 10 flashcards.

In this note

  1. Introduction
  2. Glycolysis: Importance, Chemical Reactions, and Energy Balance
  3. GLYCOLYSIS
  4. Chemical Reactions of Glycolysis
  5. Energy Balance in Anaerobic and Aerobic Conditions
  6. Tissue Specificity of Glycolysis
  7. Metabolic Fate of NADH+H+, Lactate, and Pyruvate
  8. Relations between Glycolysis and Respiratory Chains
  9. Pasteur Effect
  10. Links with the Citric Acid Cycle
  11. Lactic Acidosis
  12. Hemolytic Anemia due to Pyruvate Kinase Deficiency
  13. MCQs ☺
  14. Answers

Glycolysis: Importance, Chemical Reactions, and Energy Balance

Importance of Glycolysis

  • Fundamental Pathway: Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism.
  • Universal Pathway: Present in nearly all organisms, reflecting its evolutionary importance.
  • Anaerobic Energy Production: Allows cells to produce ATP without oxygen, crucial in anaerobic conditions.

GLYCOLYSIS

  • glucose
  1. 1 HEXOKINASE ATP → ADP
  • glucose 6-phosphate
  1. 2 PHOSPHOGLUCOISOMRASE
  • fructose 6-phosphate
  1. 3 PHOSPHOFRUCTOKINASE ATP → ADP
  • fructose 1,6-bisphosphate
  1. 4 ALDOLASE
  • glyceraldehyde 3-phosphate (G3P) ↔ dehydroxyacetone phosphate (DHAP)
  1. 5 ISOMERASE
  2. 6 TRIOSE PHOSPHATE DEHYDROGENASE 2 NAD⁺ → 2 NADH + 2 H⁺
  • 1,3-bisphosphoglycerate
  1. 7 PHOSPHOGLYCEROKINASE 2 ADP → 2 ATP
  • 3-phosphoglycerate
  1. 8 PHOSPHOGLYCEROMUTASE
  • 2-phosphoglycerate
  1. 9 ENOLASE → 2 H₂O
  • phosphoenolpyruvate (PEP)
  1. 10 PYRUVATE KINASE 2 ADP → 2 ATP
  • pyruvate

Chemical Reactions of Glycolysis

  • Ten Enzyme-Catalyzed Steps: Converts glucose to pyruvate, generating ATP and NADH.

Key Steps:

  • Phosphorylation of glucose to glucose-6-phosphate (Hexokinase).
  • Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate (Phosphofructokinase).
  • Cleavage of fructose-1,6-bisphosphate into two three-carbon molecules, and subsequent conversion to pyruvate.

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