Part V: Metabolism
Energy & Metabolic Pathways
Metabolism encompasses the entire network of chemical reactions that sustain life. Central to bioenergetics is the coupling of exergonic reactions to ATP synthesis. This part traces the major catabolic pathways: glycolysis converts glucose to pyruvate, the citric acid cycle oxidizes acetyl-CoA to CO₂, and oxidative phosphorylation harnesses the electron transport chain to generate the bulk of cellular ATP. Lipid metabolism provides an alternative high-energy fuel through β-oxidation and ketogenesis.
30–32
ATP per Glucose
−30.5 kJ/mol
ΔG°' ATP Hydrolysis
~40%
Metabolic Efficiency
Lecture Companions: Bioenergetics Foundations
Three undergraduate lectures that set up the thermodynamic and redox vocabulary used by every metabolic pathway in this part.
9A. Standard States & Metabolism (general)
9B. Redox Reactions
9C. Thermodynamic Coupling & Activation Steps
Topics in This Part
15. Thermodynamics of Life
Free energy, ATP as energy currency, coupled reactions, and the thermodynamic basis of metabolism
16. Glycolysis
The 10-step pathway from glucose to pyruvate, substrate-level phosphorylation, and regulation by PFK-1
17. The Citric Acid Cycle
Acetyl-CoA oxidation, the 8-step cycle, NADH and FADH₂ production, and anaplerotic reactions
18. Electron Transport & ATP Synthesis
Complexes I–IV, the proton motive force, chemiosmotic theory, ATP synthase rotary mechanism, and uncoupling
19. Lipid Metabolism
β-oxidation of fatty acids, ketogenesis, fatty acid synthesis, and regulation of lipid metabolism