Table of Contents ▼
1. Amino Acids & Proteins
Classification Mnemonics
- Simple: GA (Glycine, Alanine).
- Branched Chain: LIVe (Leucine, Isoleucine, Valine).
- Alcohol containing: Sero this is Alcohol (Serine, Threonine + Tyrosine).
- Aromatic (Smell): "Fan" in name + Tyrosine. (Tryptophan, Phenylalanine, Tyrosine).
Note: Tryptophan has maximum UV absorption. - Basic (+ve charge): His Last Urge (Histidine, Lysine, Arginine).
- Acidic (-ve charge): Aspartate, Glutamate.
- Essential: TV TILL 9 PMH (Histidine is essential).
- Semi-essential: Arginine.
- Ketogenic: Lucy (Leucine) & Lysine.
Clinical Disorders
- Phenylketonuria (PKU):
Deficiency: Phenylalanine Hydroxylase (Type 1).
Features: Mousy/Musty odor urine, Fair skin (low melanin), Mental retardation. - Tyrosinemia:
Type 1 (Hepatorenal): Fumarylacetoacetate hydrolase deficiency. Most severe.
Type 2 (Oculocutaneous): Tyrosine Transaminase deficiency. Palmoplantar keratosis.
Type 3: 4-HPP dioxygenase deficiency. - Alkaptonuria:
Deficiency: Homogentisate Oxidase.
Features: Black Urine on standing, Ochronosis (Joint pain + Pigmentation). - Maple Syrup Urine Disease (MSUD):
Deficiency: Branched Chain Alpha-Ketoacid Dehydrogenase.
Smell: Burnt sugar/Maple syrup.
Cystinuria: Defect in COLA transporter (Cystine, Ornithine, Lysine, Arginine).
Crystal: Hexagonal crystals in urine.
Proteins & Collagen
- Insulin: 51 Amino acids. Sequencing by Sanger (Sanger's reagent: FDNB).
Stabilizer: Zinc. Action enhancer: Chromium. - Collagen: Glycine (every 3rd AA) - Proline - Lysine.
Inside Fibroblast: Hydroxylation (Vit C dependent), Glycosylation, Triple helix.
Outside Fibroblast: Cross-linking (Lysyl Oxidase - Copper dependent).
2. Carbohydrate Metabolism
Glycolysis & Energetics
- Rate Limiting Enzyme: PFK-1 (Phosphofructokinase-1).
- Inhibitors:
- Fluoride: Inhibits Enolase (Used in glucose estimation vials).
- Iodoacetate: Inhibits G3PDH.
- Arsenite: Inhibits PDH complex.
- ATP Yield:
Aerobic: 7 ATP (or 5 ATP if Rapoport Leubering shunt).
Anaerobic (RBC): 2 ATP.
Rapoport Leubering Shunt: 0 ATP.
Glycogen Storage Diseases (GSD)
| Type | Name | Enzyme | Clinical Feature |
|---|---|---|---|
| Type 1 | Von Gierke | Glucose-6-Phosphatase | Severe Fasting Hypoglycemia, Hyperuricemia, Hyperlipidemia. |
| Type 2 | Pompe | Acid Maltase | Cardiomegaly (ECG changes), Muscle weakness. |
| Type 3 | Cori | Debranching enzyme | Liver biopsy: Branched glycogen accumulating. |
| Type 4 | Andersen | Branching enzyme | Liver biopsy: Unbranched glycogen. |
| Type 5 | McArdle | Muscle Phosphorylase | Exercise intolerance, Myoglobinuria (Dark urine after gym). |
Galactosemia vs Fructose Intolerance: "GAP FAB GUT"
- Galactosemia: GALT deficiency (Galactose-1-P Uridyl Transferase). Cataract (Oil Drop), Vomiting after breastfeed.
- Fructose Intolerance: Aldolase B deficiency. Symptoms after fruit/sucrose.
- Lactose Intolerance: Lactase deficiency. Diarrhea after milk.
3. Lipid Metabolism
Lipoprotein Disorders (Fredrickson)
- Type 1: Lipoprotein Lipase (LPL) deficiency. High Chylomicrons.
Feature: Pancreatitis, Eruptive Xanthoma. Creamy layer on plasma. - Type 2a: LDL Receptor defect (Familial Hypercholesterolemia). High LDL.
Feature: Tendon Xanthoma, Arcus juvenilis. - Type 3: Apo-E deficiency. High Remnants (IDL).
Feature: Palmar Xanthoma. - Type 4: VLDL overproduction. High Triglycerides.
Fatty Acid Oxidation
- Carnitine Shuttle: Transports Fatty Acids into Mitochondria for Beta-oxidation.
Rate Limiting Enzyme: CAT-1 (Carnitine Acyl Transferase I). - Zellweger Syndrome: Peroxisomal defect. Accumulation of Very Long Chain Fatty Acids (VLCFA).
- Refsum Disease: Defect in Alpha-oxidation (Phytanic acid oxidase). Avoid green leafy vegetables.
Ketone Bodies:
- Synthesized in Liver (Mitochondria).
- Rate Limiting Enzyme: HMG CoA Synthase.
- Primary: Acetoacetate. Most Abundant: Beta-Hydroxybutyrate.
- Not used by: Liver (lacks thiophorase) and RBC (lacks mitochondria).
4. Nucleic Acids & Molecular
Purine Metabolism
- Synthesis RLE: PRPP Glutamyl Amidotransferase.
- Lesch-Nyhan Syndrome: HGPRT deficiency (X-linked).
Features: Self-mutilation, Hyperuricemia (Gout), Orange crystals in diaper. - SCID: Adenosine Deaminase (ADA) deficiency.
DNA Repair Defects
- HNPCC (Lynch Syndrome): Mismatch Repair defect.
- Xeroderma Pigmentosum: Nucleotide Excision Repair defect (UV damage -> Thymine dimers). Skin cancer risk.
- Ataxia Telangiectasia: Non-homologous End Joining defect.
- Bloom Syndrome: Homologous Recombination defect.
Transcription/Translation
- Post-Transcriptional Modifications:
1. 5' Capping (7-Methyl Guanosine).
2. 3' Tailing (Poly-A tail).
3. Splicing (Removal of Introns).
Note: Glycation is NOT a PTM. Methylation IS a PTM. - tRNA: Clover leaf shape. Acceptor arm (CCA tail at 3' end) carries amino acid. D-arm for loading (Aminoacyl tRNA synthetase).
5. Electron Transport Chain
Inhibitors Mnemonic: "Ro M Balak Ma Kata"
- Complex I: Rotenone, Barbiturates.
- Complex II: Malonate.
- Complex III: Bal (British Anti Lewisite), Antimycin A.
- Complex IV: Cyanide, CO, H2S ("Kata").
- Complex V (ATP Synthase): Oligomycin.
- Uncouplers: 2,4-DNP (Thermogenin), Aspirin (High dose). Allow proton leak -> Heat production (Hyperthermia).
6. Enzymes & Inhibition
Lineweaver-Burk Plot Hints
- Competitive Inhibition: Vmax same, Km increases. (Lines cross at Y-axis).
Mnemonic: Competitive = Cross. - Non-Competitive: Vmax decreases, Km same. (Lines start from same point on X-axis).
- Uncompetitive: Both Vmax and Km decrease. (Parallel lines).
- Suicide Inhibition: Allopurinol on Xanthine Oxidase.
7. Vitamins
- Vitamin A: Deficiency -> Night blindness, Bitot spots. Toxicity -> Pseudotumor cerebri.
- Vitamin B1 (Thiamine): Wernicke-Korsakoff (Alcoholics), Beri-Beri.
Enzymes requiring B1: "BeAPT" (Branched chain ketoacid DH, Alpha-ketoglutarate DH, Pyruvate DH, Transketolase). - Vitamin B3 (Niacin): Deficiency -> Pellagra (3Ds: Dermatitis, Diarrhea, Dementia).
Causes: Maize eaters, Carcinoid syndrome, Hartnup disease. - Vitamin B6: Deficiency -> Sideroblastic anemia, Peripheral neuropathy (Isoniazid induced).
- Vitamin C: Scurvy (Bleeding gums), Wound healing defect.
- Vitamin K: Clotting factors (2, 7, 9, 10). Warfarin toxicity.
Tests for Carbohydrates ("Mona is in the Bar"):
- Molisch: General Carbohydrates.
- Benedict: Reducing sugars (Sucrose is Non-reducing).
- Barfoed: Monosaccharides (Mona in Bar).
- Seliwanoff: Ketohexoses (Fructose).