Biochemistry — B.Pharmacy 2nd Semester
Biochemistry is the study of chemical processes within and relating to living organisms. For pharmacy students, it provides foundational knowledge of metabolic pathways, enzyme mechanisms, and the molecular basis of disease — all essential for understanding drug action.
Unit 1: Biomolecules — Carbohydrates
Classification
- Monosaccharides: Glucose, fructose, galactose (C₆H₁₂O₆)
- Disaccharides: Sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose)
- Polysaccharides: Starch, glycogen, cellulose (polymers of glucose)
Functions
Energy source (4 kcal/g), structural components (cellulose in plants, chitin), cell recognition (glycoproteins), and precursors for biosynthesis.
Unit 2: Proteins and Amino Acids
Amino Acid Structure
All amino acids have a central α-carbon bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a variable R group. Twenty standard amino acids are encoded by the genetic code.
Protein Structure Levels
- Primary structure: Linear sequence of amino acids linked by peptide bonds
- Secondary structure: Local folding — α-helix and β-pleated sheet (hydrogen bonds)
- Tertiary structure: Overall 3D shape (hydrophobic interactions, disulfide bonds, ionic bonds)
- Quaternary structure: Arrangement of multiple polypeptide subunits (e.g., hemoglobin has 4 subunits)
Unit 3: Enzymes
Enzymes are biological catalysts that increase reaction rates by lowering activation energy. Most enzymes are proteins (except ribozymes — RNA enzymes).
Enzyme Classification (EC Numbers)
- EC 1 — Oxidoreductases: Catalyze oxidation-reduction reactions (dehydrogenases, oxidases)
- EC 2 — Transferases: Transfer functional groups (kinases, transaminases)
- EC 3 — Hydrolases: Catalyze hydrolysis reactions (lipases, proteases, phosphatases)
- EC 4 — Lyases: Cleave bonds without hydrolysis or oxidation (decarboxylases, aldolases)
- EC 5 — Isomerases: Catalyze isomerization reactions (racemases, epimerases)
- EC 6 — Ligases: Join molecules using ATP (synthetases, carboxylases)
Michaelis-Menten Kinetics
Describes enzyme kinetics: v = Vmax[S] / (Km + [S]), where Km is the substrate concentration at half-maximum velocity. Low Km = high affinity. The Lineweaver-Burk plot (1/v vs 1/[S]) linearizes this equation.
Unit 4: Metabolism
Glycolysis
10-step pathway converting glucose to 2 pyruvate molecules in the cytoplasm. Net yield: 2 ATP + 2 NADH per glucose. Key regulatory enzymes: hexokinase, PFK-1, pyruvate kinase.
Krebs Cycle (TCA Cycle)
Occurs in the mitochondrial matrix. Acetyl-CoA is oxidized to CO₂, generating 3 NADH, 1 FADH₂, and 1 GTP per turn. Two turns per glucose molecule.
Electron Transport Chain & Oxidative Phosphorylation
NADH and FADH₂ donate electrons to the ETC (inner mitochondrial membrane). Energy from electron transfer drives proton pumping, creating a gradient used by ATP synthase. Total yield: ~30-32 ATP per glucose molecule.
Unit 5: Nucleic Acids
DNA Structure
Double helix with antiparallel strands connected by complementary base pairing: Adenine-Thymine (2 hydrogen bonds) and Guanine-Cytosine (3 hydrogen bonds). Sugar: deoxyribose.
RNA Types
- mRNA: Carries genetic information from DNA to ribosomes
- tRNA: Transfers amino acids to the ribosome during translation
- rRNA: Structural and catalytic component of ribosomes
Important Exam Questions
- Classify carbohydrates with examples
- Describe the four levels of protein structure
- Explain Michaelis-Menten enzyme kinetics
- Write the steps of glycolysis with enzymes and products
- Describe the structure of DNA (Watson-Crick model)
- Classify enzymes with examples