1. Three compulsory lists that must be at your tips-
- Ketogenic and Glucogenic amino acids.
- Essential and Nonessential amino acids.
- Basic, Acidic, Sulphur containing amino acids.
2. Regulatory Enzymes of pathways e.g.
- Citrate synthesis in citric acid cycle.
- Phosphofructokinase in Glycolysis.
- Pyruvate dehydrogenase in Pyruvate Oxidation.
- Pyruvate Carboxykinase in Gluconeogenesis.
- Glycogen Synthase in Glycogenesis.
- Phosphorylase in Glycogenolysis.
- G6PD in PPP.
- HMG CoA reductase in cholesterol synthesis.
3. Search for ATP estimates e.g.,
- 8 ATP’s per Glucose molecule in Glycolysis under aerobic conditions.
- 30 ATP’s per Pyruvate molecule entering citric acid cycle.
- 129 ATP’s per palmitate undergoing b-oxidation.
4. Look for regulatory molecules and feedback inhibitions e.g.,
- Glucose-6-phosphate inhibition on hexokinase.
- Citrate’s inhibitory effect on phosphofructokinase 1.
- Alanine’s inhibitory effect on Pyruvate kinase.
- Acetyl CoA’s inhibitory effect on Pyruvate dehydrogenase.
- Long chain acyl CoA’s inhibitory effect on Acetyl CoA carboxylase.
5. Look for subcellular organelles where the reactions specifically occur.
- Enzymes of citric acid cycle in mitochondrial matrix.
- Enzymes of Glycolysis in cytosol.
- Enzymes of pentose phosphate pathway in cytosol.
- Enzymes of denovo synthesis of fatty acids in cytosol.
- Enzymes of fatty acid oxidation in mitochondria.
6. Always have a clarity regarding precise role of various lipoproteins.
- HDL is cholesterol scavenger.
- Chylomicrons carry dietary cholesterol.
- VLDL are vehicles of transport of triacylglycerol from the liver to extrahepatic tissues.
7. Vitamins and their role as coenzymes e.g.,
- Thiamine in oxidative decarboxylation.
- Niacin in dehydrogenase reactions.
- Pantothenic acid in CoA.
- Pyridoxal phosphate in muscle phosphorylase.
- Biotin in carboxylase enzymes.
- Vitamin B12 to produce succinyl CoA.
- Folate in transfer of one-carbon units.
8. Products that accumulate in metabolic disorders e.g.,
- Homogenisate in urine of Alkaptonuria patients
- Phenyl acetyl glutamine in phenylketonuria.
- Xanthurenate in Vitamin B6 deficiency.
- Branched chain ketonuria in Mapple syrup urine disease.
9. Check for key enzymes responsible for Metabolic disorders e.g.,
- Glucose-6-phosphates in von Gierkes.
- Hepatic fructokinase in essential fructosuria.
- Galactose-1-phosphate uridyl transferase in Galactosemia.
- Cystathionine-b-synthase in homocystinuria.
10. Where NADH forms, where NADPH forms, where FADH2 forms, where substrate level phosphorylation occurs e.g.,
- FADH2 in succinate dehydrogenase in citric acid cycle.
- NADH in all degradative reactions.
- NADPH in all synthetic reactions.
