Krebs Cycle

The Krebs cycle (citric acid cycle) is the canonical concrete instantiation of the Life Loop Class — an eight-step closed orbit in metabolite-concentration space that preserves cellular distinction, regenerates oxaloacetate, and exhibits both a nontrivial source winding (energy carrier production) and a nontrivial closure winding (catalytic scaffold recycling).

Categorical invariant. Krebs cycle = (D, γ_Krebs, h_Krebs) ∈ Loop_L with w_γ ≠ 0 and w_η ≠ 0 — a distinguished representative of the Life Loop Class projecting nontrivially onto both Loop_src and Loop_rec.

Primary registry anchor: VI.P11

Supporting items: VI.D10, VI.D13, VI.D14, VI.T05, VI.T09

1. I.K0 — Universe Postulate
2. VI.D15 — Life Sector
3. VI.D10 — Life Loop Class — closed orbit definition
4. VI.T05 — Metabolic Fiber Theorem — source/closure winding decomposition
5. VI.P11 — Krebs cycle satisfies Loop_L with both windings nonzero

Biomarker: Citrate, isocitrate, α-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, oxaloacetate concentrations; cycle flux measured via ¹³C-isotopomer flux analysis; per-acetyl-CoA yield 3 NADH + 1 FADH₂ + 1 GTP + 2 CO₂.

Measurable range: Mitochondrial matrix flux ~0.5-2 μmol·min⁻¹·mg⁻¹ protein in cardiac/hepatic tissue; cycle period ~10-30 s per turn at physiological [substrate]; OAA regeneration verified by closure of the homotopy class h_Krebs.

Observation method: ¹³C-MFA (Metabolic Flux Analysis) with [1,2-¹³C]glucose tracers; LC-MS quantification of TCA intermediates; Seahorse oxygen-consumption coupled to NADH/FADH₂ throughput; isotopomer enrichment of OAA confirms closure.

Calibration anchor: LG-Y02-kinetic-pseudoscalar-channel

Anchor chain:

1. VI.L18 chirality channel
2. stereospecificity of all eight TCA enzymes (e.g. aconitase preserves L-isocitrate)
3. D-sugar / L-amino-acid handedness inherited at every metabolite step

Manuscript reference: manuscript-sources/book-06/part03/ch19-metabolism.tex

Status: Planned

Related glossary entries

• LG-P01-metabolism Metabolism
• LG-E01-atp ATP/ADP Oscillation
• LG-Y02-kinetic-pseudoscalar-channel Kinetic Pseudoscalar Channel

Referenced by

• LG-P03-glycolysis Glycolysis
• LG-P05-respiration Cellular Respiration