📂 Master Index: Metabolism & Bioenergetics
I. Foundations of Bioenergetics
● Thermodynamics: Gibbs Free Energy ($\Delta G$), Exergonic vs. Endergonic
reactions.
● Energy Coupling: How ATP hydrolysis drives unfavorable reactions.
● Redox Carriers: The roles of NAD+, FAD, and NADPH.
II. Carbohydrate Metabolism (The Central Hub)
● Glycolysis: Rate-limiting step (PFK-1), the "Big Three" irreversible enzymes.
● Gluconeogenesis: The bypass enzymes and the role of Fructose-1,6-bisphosphatase.
● Glycogen Dynamics: Glycogenolysis vs. Glycogenesis; The role of Glycogen
Phosphorylase.
● The HMP Shunt: Oxidative vs. Non-oxidative phases; G6PD and NADPH production.
III. Mitochondrial Pathways
● The PDH Complex: The five essential cofactors ($B_1, B_2, B_3, B_5$, Lipoic Acid).
● The Citric Acid Cycle (TCA): Yield per Acetyl-CoA and rate-limiting Isocitrate
Dehydrogenase.
● Oxidative Phosphorylation: The Electron Transport Chain (Complexes I-V).
● ETC Pharmacology: Inhibitors (Cyanide/CO) vs. Uncouplers (DNP/Aspirin).
IV. Lipid & Protein Metabolism
● Beta-Oxidation: The Carnitine Shuttle and MCAD deficiency.
● Fatty Acid Synthesis: Acetyl-CoA Carboxylase and Malonyl-CoA regulation.
● Ketogenesis: The "Alternative Fuel" logic and why the liver can't use them
(Thiophorase).
● The Urea Cycle: Detoxifying ammonia and the "Krebs Bicycle" link to TCA.
V. Clinical Correlations & Pathology
● Glycogen Storage Diseases (GSD): Von Gierke (I), Pompe (II), Cori (III), McArdle (V).
● Metabolic Shifts: The Ethanol Redox Shift (high NADH) and the Warburg Effect
(Cancer).
● Amino Acid Disorders: PKU, Hartnup Disease, and Albinism.
● Inborn Errors: Maple Syrup Urine Disease and Organic Acidemias.
VI. Hormonal & Tissue Integration
● The Insulin/Glucagon Ratio: Phosphorylation (PKA) vs. Dephosphorylation (PP1).
● Organ Preferences: Brain (Glucose/Ketones) vs. Heart (Fatty Acids) vs. RBCs
(Glucose only).
● Nucleotide Metabolism: Purine/Pyrimidine synthesis and the Lesch-Nyhan salvage
defect.
, ● 1-Carbon Metabolism: The Folate/B12 Trap and Megaloblastic Anemia.
VII. Visual Study Aids (Generated Blueprints)
1. Overview: Catabolism vs. Anabolism.
2. Regulation: PFK-1 and the F-2,6-BP "Master Switch."
3. Complex Cycles: The Krebs Bicycle (Urea + TCA).
4. Clinical: Alcohol Metabolism Shunts and Redox states.
5. Molecular: The Folate Trap and Nucleotide Salvage.
6. Specialization: Tissue-specific fuel preferences and Cancer metabolism.
,"food equals fuel" idea and look at it as a massive, interconnected web of redox reactions and
signal transduction.
Here is the breakdown of Bioenergetics, Catabolism, and Anabolism, scaled from foundational
concepts to high-yield clinical correlations.
1. Bioenergetics: The Thermodynamics of Life
Bioenergetics predicts whether a reaction will occur based on energy changes, not speed
(which is controlled by enzymes).
● Gibbs Free Energy ($\Delta G$): This determines spontaneity.
○ Exergonic ($-\Delta G$): Spontaneous reactions that release energy.
○ Endergonic ($+\Delta G$): Non-spontaneous reactions that require energy
input.
, ● Energy Coupling: The body drives endergonic reactions (like building muscle) by
"coupling" them to the exergonic hydrolysis of ATP.
● Redox Potentials ($E_0$): Metabolism is essentially the movement of electrons from
food (glucose/fats) to oxygen. The "Electron Motive Force" is what ultimately builds the
ATP gradient.
2. Catabolism: The Breakdown (Energy Harvest)
Catabolism occurs in three stages: hydrolysis of macromolecules, conversion to Acetyl-CoA,
and finally, oxidation to $CO_2$ and $H_2O$.
A. Glycolysis (Cytosol)
The conversion of 1 Glucose to 2 Pyruvate.
● Key Regulatory Steps: 1. Hexokinase/Glucokinase: (First trap).
2. Phosphofructokinase-1 (PFK-1): The rate-limiting step, inhibited by ATP and Citrate,
activated by AMP and Fructose-2,6-bisphosphate.
3. Pyruvate Kinase.
● Clinical Pearl: In RBCs (which lack mitochondria), glycolysis is the only source of ATP.
A deficiency in Pyruvate Kinase leads to Hemolytic Anemia.
+1
B. The Citric Acid Cycle / Krebs (Mitochondrial Matrix)
Acetyl-CoA joins Oxaloacetate to form Citrate.
● Yield per turn: 3 NADH, 1 $FADH_2$, 1 GTP, and 2 $CO_2$.
● Rate-limiting enzyme: Isocitrate Dehydrogenase.
● Advanced Note: The cycle is amphibolic, meaning it provides intermediates for both
catabolism and anabolism (e.g., Succinyl-CoA is used for Heme synthesis).
3. Oxidative Phosphorylation: The ATP Factory
This takes place in the inner mitochondrial membrane (IMM) and consists of the Electron
Transport Chain (ETC) and Chemiosmosis.
The Electron Transport Chain
Electrons from NADH and $FADH_2$ are passed through four complexes:
1. Complex I (NADH Dehydrogenase): Pumps protons ($H^+$).
2. Complex II (Succinate Dehydrogenase): Does NOT pump protons.
3. Complex III (Cytochrome bc1): Pumps protons.
4. Complex IV (Cytochrome c Oxidase): Transfers electrons to $O_2$ (the final
acceptor) to form $H_2O$. Pumps protons.
I. Foundations of Bioenergetics
● Thermodynamics: Gibbs Free Energy ($\Delta G$), Exergonic vs. Endergonic
reactions.
● Energy Coupling: How ATP hydrolysis drives unfavorable reactions.
● Redox Carriers: The roles of NAD+, FAD, and NADPH.
II. Carbohydrate Metabolism (The Central Hub)
● Glycolysis: Rate-limiting step (PFK-1), the "Big Three" irreversible enzymes.
● Gluconeogenesis: The bypass enzymes and the role of Fructose-1,6-bisphosphatase.
● Glycogen Dynamics: Glycogenolysis vs. Glycogenesis; The role of Glycogen
Phosphorylase.
● The HMP Shunt: Oxidative vs. Non-oxidative phases; G6PD and NADPH production.
III. Mitochondrial Pathways
● The PDH Complex: The five essential cofactors ($B_1, B_2, B_3, B_5$, Lipoic Acid).
● The Citric Acid Cycle (TCA): Yield per Acetyl-CoA and rate-limiting Isocitrate
Dehydrogenase.
● Oxidative Phosphorylation: The Electron Transport Chain (Complexes I-V).
● ETC Pharmacology: Inhibitors (Cyanide/CO) vs. Uncouplers (DNP/Aspirin).
IV. Lipid & Protein Metabolism
● Beta-Oxidation: The Carnitine Shuttle and MCAD deficiency.
● Fatty Acid Synthesis: Acetyl-CoA Carboxylase and Malonyl-CoA regulation.
● Ketogenesis: The "Alternative Fuel" logic and why the liver can't use them
(Thiophorase).
● The Urea Cycle: Detoxifying ammonia and the "Krebs Bicycle" link to TCA.
V. Clinical Correlations & Pathology
● Glycogen Storage Diseases (GSD): Von Gierke (I), Pompe (II), Cori (III), McArdle (V).
● Metabolic Shifts: The Ethanol Redox Shift (high NADH) and the Warburg Effect
(Cancer).
● Amino Acid Disorders: PKU, Hartnup Disease, and Albinism.
● Inborn Errors: Maple Syrup Urine Disease and Organic Acidemias.
VI. Hormonal & Tissue Integration
● The Insulin/Glucagon Ratio: Phosphorylation (PKA) vs. Dephosphorylation (PP1).
● Organ Preferences: Brain (Glucose/Ketones) vs. Heart (Fatty Acids) vs. RBCs
(Glucose only).
● Nucleotide Metabolism: Purine/Pyrimidine synthesis and the Lesch-Nyhan salvage
defect.
, ● 1-Carbon Metabolism: The Folate/B12 Trap and Megaloblastic Anemia.
VII. Visual Study Aids (Generated Blueprints)
1. Overview: Catabolism vs. Anabolism.
2. Regulation: PFK-1 and the F-2,6-BP "Master Switch."
3. Complex Cycles: The Krebs Bicycle (Urea + TCA).
4. Clinical: Alcohol Metabolism Shunts and Redox states.
5. Molecular: The Folate Trap and Nucleotide Salvage.
6. Specialization: Tissue-specific fuel preferences and Cancer metabolism.
,"food equals fuel" idea and look at it as a massive, interconnected web of redox reactions and
signal transduction.
Here is the breakdown of Bioenergetics, Catabolism, and Anabolism, scaled from foundational
concepts to high-yield clinical correlations.
1. Bioenergetics: The Thermodynamics of Life
Bioenergetics predicts whether a reaction will occur based on energy changes, not speed
(which is controlled by enzymes).
● Gibbs Free Energy ($\Delta G$): This determines spontaneity.
○ Exergonic ($-\Delta G$): Spontaneous reactions that release energy.
○ Endergonic ($+\Delta G$): Non-spontaneous reactions that require energy
input.
, ● Energy Coupling: The body drives endergonic reactions (like building muscle) by
"coupling" them to the exergonic hydrolysis of ATP.
● Redox Potentials ($E_0$): Metabolism is essentially the movement of electrons from
food (glucose/fats) to oxygen. The "Electron Motive Force" is what ultimately builds the
ATP gradient.
2. Catabolism: The Breakdown (Energy Harvest)
Catabolism occurs in three stages: hydrolysis of macromolecules, conversion to Acetyl-CoA,
and finally, oxidation to $CO_2$ and $H_2O$.
A. Glycolysis (Cytosol)
The conversion of 1 Glucose to 2 Pyruvate.
● Key Regulatory Steps: 1. Hexokinase/Glucokinase: (First trap).
2. Phosphofructokinase-1 (PFK-1): The rate-limiting step, inhibited by ATP and Citrate,
activated by AMP and Fructose-2,6-bisphosphate.
3. Pyruvate Kinase.
● Clinical Pearl: In RBCs (which lack mitochondria), glycolysis is the only source of ATP.
A deficiency in Pyruvate Kinase leads to Hemolytic Anemia.
+1
B. The Citric Acid Cycle / Krebs (Mitochondrial Matrix)
Acetyl-CoA joins Oxaloacetate to form Citrate.
● Yield per turn: 3 NADH, 1 $FADH_2$, 1 GTP, and 2 $CO_2$.
● Rate-limiting enzyme: Isocitrate Dehydrogenase.
● Advanced Note: The cycle is amphibolic, meaning it provides intermediates for both
catabolism and anabolism (e.g., Succinyl-CoA is used for Heme synthesis).
3. Oxidative Phosphorylation: The ATP Factory
This takes place in the inner mitochondrial membrane (IMM) and consists of the Electron
Transport Chain (ETC) and Chemiosmosis.
The Electron Transport Chain
Electrons from NADH and $FADH_2$ are passed through four complexes:
1. Complex I (NADH Dehydrogenase): Pumps protons ($H^+$).
2. Complex II (Succinate Dehydrogenase): Does NOT pump protons.
3. Complex III (Cytochrome bc1): Pumps protons.
4. Complex IV (Cytochrome c Oxidase): Transfers electrons to $O_2$ (the final
acceptor) to form $H_2O$. Pumps protons.
