Metabolic Pathways
Energy production, biosynthesis, and catabolism
Glycolysis
The breakdown of glucose into pyruvate, yielding ATP and NADH.
Citric Acid Cycle (Krebs Cycle)
Oxidizes acetyl-CoA to CO₂, generating GTP, NADH, and FADH₂.
Oxidative Phosphorylation
Electron transport chain coupled to ATP synthesis via chemiosmosis.
Pentose Phosphate Pathway
Generates NADPH and ribose-5-phosphate for biosynthesis.
β-Oxidation of Fatty Acids
Sequential removal of 2-carbon units from fatty acids as acetyl-CoA.
Photosynthesis – Light Reactions
Capture of light energy to produce ATP and NADPH, with O₂ as a byproduct.
Calvin Cycle (Light-Independent Reactions)
Fixes CO₂ into organic molecules using ATP and NADPH from light reactions.
Gluconeogenesis
Synthesis of glucose from non-carbohydrate precursors.
Glycogen Metabolism
Synthesis and degradation of glycogen for glucose storage and release.
Urea Cycle
Converts toxic ammonia to urea for excretion.
Amino Acid Catabolism
Degradation of amino acids to metabolic intermediates and ammonia.
Nucleotide Biosynthesis
De novo and salvage pathways for purine and pyrimidine nucleotide production.
Folate / One-Carbon Metabolism
Transfer of one-carbon units for nucleotide synthesis, methylation, and amino acid metabolism.
Heme Biosynthesis
Eight-step pathway producing heme from glycine and succinyl-CoA.
Ketogenesis
Hepatic production of ketone bodies from excess acetyl-CoA during fasting.
Fermentation (Anaerobic)
Regeneration of NAD⁺ from NADH under anaerobic conditions.
Glyoxylate Cycle
Net conversion of acetyl-CoA to oxaloacetate, bypassing CO₂ loss steps of TCA.
Nitrogen Fixation
Reduction of atmospheric N₂ to ammonia by nitrogenase.
CAM Photosynthesis
Temporal separation of CO₂ fixation (night) and Calvin cycle (day) to conserve water.
C4 Photosynthesis
Spatial separation of initial CO₂ fixation and Calvin cycle to concentrate CO₂.