Biochemistry — 30-Min Notes

1. Carbohydrate Metabolism

• Glycolysis: glucose → pyruvate; key enzymes: hexokinase, phosphofructokinase, pyruvate kinase.

• Gluconeogenesis: pyruvate → glucose; bypasses irreversible glycolysis steps; key enzymes: pyruvate carboxylase, PEP carboxykinase.

• High-yield: Glycogen storage diseases → type I (von Gierke), type II (Pompe), type III (Cori)

• Tip: Insulin ↑ glucose uptake; glucagon ↑ gluconeogenesis and glycogenolysis

• PPP (pentose phosphate pathway) → generates NADPH for fatty acid synthesis and ribose-5-phosphate for nucleotides

2. Lipid Metabolism

• β-oxidation: fatty acids → acetyl-CoA in mitochondria; generates NADH and FADH2 for ATP.

• Ketone bodies: acetoacetate, β-hydroxybutyrate, acetone; produced in liver during fasting or diabetes.

• High-yield: Essential fatty acids → linoleic (ω-6), linolenic (ω-3); deficiency → dermatitis, poor wound healing

• Cholesterol metabolism: HMG-CoA reductase → rate-limiting enzyme; statins inhibit this enzyme

• Tip: Lipoproteins → chylomicrons, VLDL, LDL, HDL; transport triglycerides and cholesterol

3. Protein & Amino Acid Metabolism

• Transamination: amino group transferred to α-ketoglutarate → glutamate; key enzyme: aminotransferases.

• Urea cycle → liver converts ammonia → urea; key enzymes: carbamoyl phosphate synthetase, ornithine transcarbamylase.

• High-yield: Phenylketonuria → deficiency of phenylalanine hydroxylase → mental retardation if untreated

• Tip: Essential amino acids → PVT TIM HALL (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine)

• Glutathione → antioxidant; requires NADPH from PPP for regeneration

4. Enzymes & Coenzymes

• Enzymes → biological catalysts; follow Michaelis-Menten kinetics.

• Coenzymes: NAD+, NADP+, FAD, CoA; derived from vitamins B1, B2, B3, B5.

• High-yield: Km → substrate concentration at ½ Vmax; Vmax → maximum velocity

• Tip: Competitive inhibitor ↑ Km, same Vmax; Non-competitive ↓ Vmax, same Km

• Enzyme deficiency → clinical disorders: G6PD deficiency → hemolytic anemia

5. Nucleic Acids & Molecular Biology

• DNA replication → semi-conservative; enzymes: DNA polymerase, helicase, ligase, primase.

• Transcription → RNA synthesis; translation → protein synthesis; genetic code is universal.

• High-yield: Mutation types → point mutation (silent, missense, nonsense), frameshift; key in genetic diseases

• Tip: PCR amplifies DNA; restriction enzymes cut DNA at specific sequences

• mRNA, tRNA, rRNA → essential for protein synthesis; rRNA forms ribosome structure

6. Vitamins & Minerals

• Water-soluble: B-complex, C; Fat-soluble: A, D, E, K.

• High-yield: Vitamin deficiencies → B1 (Beriberi), B12 (pernicious anemia), C (scurvy), D (rickets)

• Calcium, phosphate → bone mineralization; magnesium → cofactor for enzymes

• Tip: Iron → hemoglobin synthesis; deficiency → microcytic anemia

• Trace elements: Zn, Cu, Se, I → enzymatic function and thyroid hormone synthesis

7. High-Yield Repeated Points (NEET MDS)

• Glycogen storage diseases → type I, II, III

• Essential fatty acids → linoleic (ω-6), linolenic (ω-3)

• Phenylketonuria → mental retardation if untreated

• Coenzymes → NAD+, FAD, CoA; derived from B vitamins

• Enzyme kinetics → Km & Vmax; inhibitors

• Vitamin deficiencies → B1, B12, C, D

• PPP → NADPH generation → antioxidant defense