Fetch all the images of all the metabolic cycles in biochemistry and integrate into one in an order

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All 10 metabolic cycle images have been successfully retrieved. Here they are organized in the correct metabolic order - from fuel intake through energy extraction:

Integrated Metabolic Cycles of Biochemistry

The major metabolic cycles are interconnected in a logical flow: dietary fuels (glucose, fatty acids, amino acids) are broken down stepwise, with electrons ultimately passed to oxygen via the electron transport chain to generate ATP. Here they are presented in sequence.

1. Glycolysis - Glucose 6-Phosphate Branch Point

Glucose enters metabolism via phosphorylation to Glucose-6-Phosphate (G-6-P), the central hub that feeds into glycolysis, the pentose phosphate pathway, or glycogen synthesis.

Glucose-6-P as metabolic branch point - Basic Medical Biochemistry

Fig. 22.5 - Glucose 6-P metabolism and its branch pathways (Basic Medical Biochemistry, 6e)

2. Glycolysis - Two-Phase Pathway

Glycolysis converts glucose to 2 pyruvate in two phases: a preparative (energy-investing) phase and an ATP-generating phase.

Glycolysis two phases - Basic Medical Biochemistry

Fig. 22.4 - Phases of glycolysis: net yield is 2 ATP + 2 NADH + 2 pyruvate per glucose (Basic Medical Biochemistry, 6e)

3. Pentose Phosphate Pathway (Hexose Monophosphate Shunt)

The alternative oxidative route for Glucose-6-P, generating NADPH for reductive biosynthesis and antioxidant defense, and ribose-5-phosphate for nucleotide synthesis. It links to glutathione recycling in red blood cells.

Pentose phosphate pathway and glutathione cycle - Harper's Biochemistry

Fig. 20-3 - The pentose phosphate pathway driving the glutathione peroxidase reaction to protect erythrocytes from oxidative damage (Harper's Illustrated Biochemistry, 32e)

4. Citric Acid (Krebs) Cycle - Overview

Pyruvate from glycolysis is converted to Acetyl-CoA, which enters the TCA cycle. Two carbons enter as Acetyl-CoA; two leave as CO₂. Oxaloacetate is regenerated each turn.

TCA cycle overview - Harper's Biochemistry

Fig. 16-1 - The citric acid cycle: Acetyl-CoA + Oxaloacetate → Citrate → regenerates Oxaloacetate + 2 CO₂ (Harper's Illustrated Biochemistry, 32e)

5. Citric Acid (Krebs) Cycle - Linked to Respiratory Chain

The same cycle shown with its connection to the respiratory chain, illustrating how NADH and FADH₂ produced per turn feed oxidative phosphorylation to generate 9 ATP (+ 1 GTP) per acetyl-CoA.

TCA cycle with respiratory chain linkage - Harper's Biochemistry

Fig. 16-2 - TCA cycle feeding the respiratory chain for ATP synthesis via oxidative phosphorylation (Harper's Illustrated Biochemistry, 32e)

6. Citric Acid (Krebs) Cycle - Full Enzymatic Detail

The complete cycle showing all intermediates, enzymes (citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate thiokinase, succinate dehydrogenase, fumarase, malate dehydrogenase), and inhibition sites (fluoroacetate, malonate, arsenite).

TCA cycle full detail with enzymes - Harper's Biochemistry

Fig. 16-3 - The complete Krebs cycle with all enzymes, cofactors, and inhibition sites labeled (Harper's Illustrated Biochemistry, 32e)

7. Fatty Acid Beta-Oxidation - Carnitine Shuttle (Entry Step)

Long-chain fatty acids cannot cross the inner mitochondrial membrane on their own. They are shuttled as acylcarnitine by CPT-I and CPT-II across both membranes before entering beta-oxidation in the matrix.

Carnitine shuttle for fatty acid transport - Lippincott Biochemistry

Fig. 16.16 - Carnitine shuttle: transport of long-chain fatty acyl-CoA into mitochondria for beta-oxidation (Lippincott Illustrated Reviews: Biochemistry, 8e)

8. Fatty Acid Beta-Oxidation - Energy Yield

Each cycle of beta-oxidation removes 2 carbons as acetyl-CoA, producing FADH₂ and NADH. Full oxidation of palmitate (16C) yields 129 net ATP, linking beta-oxidation to the TCA cycle and oxidative phosphorylation.

Beta-oxidation energy yield for palmitate - Lippincott Biochemistry

Fig. 16.18 - Beta-oxidation of palmitoyl-CoA: 7 FADH₂ (14 ATP) + 7 NADH (21 ATP) + 8 Acetyl-CoA via TCA (96 ATP) = 131 − 2 activation = 129 net ATP (Lippincott Illustrated Reviews: Biochemistry, 8e)

9. Urea Cycle - Nitrogen Disposal

Amino acid catabolism generates ammonia (toxic), which is detoxified in the liver via the urea cycle. Nitrogen enters as NH₄⁺ (→ carbamoyl phosphate) and aspartate; urea is released to urine. The cycle spans both mitochondria and cytosol. Fumarate produced links back to the TCA cycle.

Fig. 36.10 - Urea cycle showing 5 steps (CPSI → OTC → Argininosuccinate synthetase → Argininosuccinate lyase → Arginase), mitochondrial/cytosolic compartments, and fumarate production (Basic Medical Biochemistry, 6e)

10. Electron Transport Chain (Oxidative Phosphorylation)

The final common pathway. NADH and FADH₂ from all cycles above donate electrons through Complexes I-IV in the inner mitochondrial membrane, driving proton pumping and ATP synthesis. O₂ is the final electron acceptor, reduced to H₂O.

Electron transport chain - Lippincott Biochemistry

Fig. 6.8 - The mitochondrial electron transport chain (Complexes I-IV), CoQ, and cytochrome c, terminating in O₂ reduction to H₂O (Lippincott Illustrated Reviews: Biochemistry, 8e)

How the Cycles Connect

Pathway	Input	Output	Links to
Glycolysis	Glucose	2 Pyruvate, 2 NADH, 2 ATP	TCA cycle, Pentose phosphate pathway
Pentose Phosphate Pathway	Glucose-6-P	NADPH, Ribose-5-P	Nucleotide synthesis, antioxidant defense
TCA Cycle	Acetyl-CoA	3 NADH, 1 FADH₂, 1 GTP, 2 CO₂	Electron transport chain; Urea cycle (fumarate)
Beta-Oxidation	Fatty acyl-CoA	Acetyl-CoA, NADH, FADH₂	TCA cycle, ETC
Urea Cycle	NH₄⁺, Aspartate	Urea (excreted), Fumarate	TCA cycle (fumarate → malate)
Electron Transport Chain	NADH, FADH₂, O₂	H₂O, ATP (bulk)	Final output of all other cycles

All images sourced from Harper's Illustrated Biochemistry (32e), Lippincott Illustrated Reviews: Biochemistry (8e), and Basic Medical Biochemistry: A Clinical Approach (6e).

Also integrate protein and lipid metabolism cycles with this

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