An overview of the fundamental concepts in biochemistry, including the structure and function of biomolecules such as proteins, carbohydrates, lipids, and nucleic acids.
Introduction to Biochemical Principles
Course‑level overview – suitable for first‑year undergraduates or anyone new to biochemistry.
1. What Is Biochemistry?
| Aspect |
Description |
| Definition |
The study of the chemical processes and substances that occur within living organisms. |
| Scope |
Includes metabolism, enzyme catalysis, signal transduction, genetic information flow, and the structure–function relationship of biomolecules. |
| Goal |
Explain how molecular-level events give rise to cellular and organismal physiology. |
2. Major Classes of Biomolecules
| Class |
Key Examples |
Primary Functions |
| Carbohydrates |
Glucose, glycogen, cellulose |
Energy storage & supply; structural components; recognition molecules. |
| Lipids |
Fatty acids, phospholipids, sterols |
Membrane formation, energy storage, signaling molecules. |
| Proteins |
Enzymes, antibodies, receptors, structural proteins |
Catalysis, transport, signaling, structural support, regulation. |
| Nucleic Acids |
DNA, RNA |
Genetic information storage, transmission, and expression. |
| Small Metabolites |
ATP, NAD⁺, coenzymes |
Energy carriers, redox reactions, co‑factor roles. |
3. Fundamental Concepts
3.1. Structure ↔ Function
- Primary structure → amino‑acid sequence (proteins) or nucleotide sequence (nucleic acids).
- Secondary structure → α‑helices, β‑sheets (proteins); double helix (DNA).
- Tertiary & Quaternary structure → 3‑D folding, subunit assembly → determines catalytic sites, binding pockets.
- Conformation changes often regulate activity (e.g., allosteric enzymes).
3.2. Thermodynamics in Biochemistry
| Term |
Meaning in Biological Context |
| ΔG (Gibbs free energy) |
Determines spontaneity of a reaction; ΔG < 0 → favorable. |
| ΔG°′ (standard free energy) |
Free energy change under standard biochemical conditions (pH 7.0, 1 M concentrations). |
| Coupled reactions |
Unfavorable reactions (positive ΔG) are driven by favorable ones (e.g., ATP hydrolysis). |
| Equilibrium constant (K_eq) |
Relates to ΔG°′: ΔG°′ = –RT ln K_eq. |
3.3. Enzyme Kinetics
- Michaelis–Menten equation: ( v = \frac{V_{\max}[S]}{K_m + [S]} )
- Vmax: maximal velocity (all enzyme active sites saturated).
- Km: substrate concentration at ½ Vmax (inverse measure of affinity).
- Lineweaver‑Burk plot (double‑reciprocal) useful for visualizing kinetic parameters.
- Inhibition types: competitive, non‑competitive, uncompetitive, mixed; each alters Km and/or Vmax differently.
3.4. Metabolic Pathways
- Catabolism → breakdown of molecules → release of energy (e.g., glycolysis, β‑oxidation).
- Anabolism → synthesis of complex molecules → consumes energy (e.g., fatty‑acid synthesis, nucleotide biosynthesis).
- Regulation: allosteric effectors, cov