Human Metabolism & Biochemistry

The Chemical Engine of Life — From Enzymes to Energy

Welcome to Human Metabolism

This course explores the intricate network of chemical reactions that sustain human life. From the thermodynamic principles governing biochemical transformations to the hormonal signals that orchestrate metabolic flux across organs, you will develop a rigorous understanding of how the human body extracts energy from nutrients, synthesizes essential biomolecules, and maintains metabolic homeostasis.

Approaching metabolism from a biochemistry perspective, we examine each pathway at the molecular level — tracing carbon atoms through enzymatic reactions, quantifying free energy changes, and understanding how allosteric regulation, covalent modification, and gene expression control metabolic output. Whether you are a student of biochemistry, medicine, or the life sciences, this course provides the foundation for understanding how metabolic dysfunction leads to disease.

6 PartsEnzyme KineticsMetabolic PathwaysClinical ConnectionsInteractive Simulations

What You'll Learn

Bioenergetics

• Gibbs free energy and spontaneity in biological systems
• ATP as the universal energy currency
• Coupled reactions and high-energy intermediates
• Redox potential and electron carriers (NAD+, FAD)

Enzyme Mechanisms

• Michaelis-Menten kinetics and steady-state analysis
• Competitive, uncompetitive, and mixed inhibition
• Allosteric enzymes and sigmoidal kinetics
• Coenzymes, cofactors, and prosthetic groups

Catabolic Pathways

• Glycolysis, pyruvate dehydrogenase, and the TCA cycle
• Fatty acid beta-oxidation and ketogenesis
• Amino acid catabolism and the urea cycle
• Electron transport chain and oxidative phosphorylation

Metabolic Regulation

• Hormonal control: insulin, glucagon, epinephrine, cortisol
• Fed versus fasted metabolic states
• Organ-specific metabolism (liver, muscle, brain, adipose)
• Metabolic disease: diabetes, obesity, inborn errors

Course Overview

Part I: Foundations of Metabolism

Thermodynamics of living systems, Gibbs free energy and reaction coupling, enzyme kinetics (Michaelis-Menten and beyond), metabolic regulation principles, coenzymes and cofactors.

Topics: free energy, enthalpy, entropy, ATP hydrolysis, enzyme catalysis, K_m, V_max, allosteric regulation

Part II: Carbohydrate Metabolism

Glycolysis and its regulation, gluconeogenesis, the pentose phosphate pathway, glycogen metabolism, and hormonal regulation by insulin and glucagon.

Topics: hexokinase, PFK-1, pyruvate kinase, Cori cycle, glycogen phosphorylase, G6PD

Part III: TCA Cycle & Oxidative Phosphorylation

The citric acid cycle as a metabolic hub, the electron transport chain complexes I-IV, chemiosmotic coupling, ATP synthase rotary mechanism, and reactive oxygen species.

Topics: citrate synthase, isocitrate dehydrogenase, Complex I-IV, proton motive force, P/O ratio, superoxide dismutase

Part IV: Lipid Metabolism

Fatty acid beta-oxidation and energy yield, de novo fatty acid synthesis, cholesterol biosynthesis and regulation, ketone body metabolism, and lipoprotein transport (chylomicrons, VLDL, LDL, HDL).

Topics: carnitine shuttle, acyl-CoA dehydrogenase, ACC, HMG-CoA reductase, statins, ketogenesis

Part V: Amino Acid & Nucleotide Metabolism

Transamination and oxidative deamination, the urea cycle and nitrogen balance, amino acid degradation pathways (glucogenic vs ketogenic), and purine and pyrimidine biosynthesis and salvage.

Topics: aminotransferases, glutamate dehydrogenase, carbamoyl phosphate synthetase, PRPP, dihydrofolate reductase

Part VI: Metabolic Integration & Regulation

Hormonal control of metabolic pathways, fed vs fasted states and the absorptive/postabsorptive transition, diabetes mellitus (type 1 and type 2), exercise metabolism, and organ-specific metabolic profiles.

Topics: insulin signaling, AMPK, mTOR, metabolic syndrome, starvation adaptation, liver-muscle-adipose crosstalk

Central Equations of Metabolism

Metabolic biochemistry rests on quantitative relationships between substrate concentrations, enzyme rates, and thermodynamic driving forces. These core equations appear throughout the course.

Gibbs Free Energy Change

The actual free energy change under cellular conditions determines whether a reaction proceeds spontaneously:

$$\Delta G = \Delta G^{\circ\prime} + RT \ln \frac{[\text{Products}]}{[\text{Reactants}]}$$

Where $\Delta G^{\circ\prime}$ is the standard free energy change at pH 7, R = 8.314 J/(mol K), and T is the absolute temperature. Reactions with $\Delta G < 0$ are thermodynamically favorable.

Michaelis-Menten Equation

The fundamental equation of enzyme kinetics relating reaction velocity to substrate concentration:

$$v = \frac{V_{\max}[S]}{K_m + [S]}$$

K_m is the substrate concentration at which the velocity is half of V_max. A low K_m indicates high substrate affinity. The catalytic efficiency is measured by k_cat/K_m.

Nernst Equation & Redox Potential

The free energy available from electron transfer in the electron transport chain depends on the difference in reduction potentials:

$$\Delta G^{\circ\prime} = -nF\Delta E^{\circ\prime}$$

Where n is the number of electrons transferred, F is Faraday's constant (96,485 C/mol), and $\Delta E^{\circ\prime}$ is the difference in standard reduction potentials. This drives proton pumping across the inner mitochondrial membrane.

Interactive Simulations

Explore metabolic pathways and enzyme kinetics through interactive simulation programs that let you manipulate substrate concentrations, enzyme parameters, and regulatory signals in real time.

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Simulation Programs

Enzyme kinetics simulators, metabolic flux calculators, ATP yield estimators, and pathway visualization tools — all with adjustable parameters and graphical output.

Major Metabolic Pathways at a Glance

Pathway	Location	Function	Key Enzyme
Glycolysis	Cytoplasm	Glucose to pyruvate	PFK-1
TCA Cycle	Mitochondrial matrix	Acetyl-CoA oxidation	Isocitrate DH
Oxidative Phosphorylation	Inner mito. membrane	ATP synthesis	ATP synthase
Beta-oxidation	Mitochondrial matrix	Fatty acid breakdown	Acyl-CoA DH
Gluconeogenesis	Cytoplasm / mito.	Glucose synthesis	PEPCK
Urea Cycle	Liver (mito. + cytoplasm)	Nitrogen disposal	CPS I
Pentose Phosphate	Cytoplasm	NADPH & ribose-5-P	G6PD

Prerequisites

Recommended Background

• General chemistry (reactions, equilibrium, thermodynamics)
• Organic chemistry (functional groups, reaction mechanisms)
• Basic cell biology (organelles, membranes)
• Introductory biochemistry (amino acids, proteins, nucleic acids)