metabolism

• Peptide bond


  Bond formed when the carboxyl (-COOH) group of one amino acid reacts with the amino (-NH2) group of the next amino acid with the elimination of a water moiety
• Glycosidic bond


  Bond formed between two carbon atoms of two adjacent monosaccharides in a polysaccharide
• Phosphodiester bond


  Bond between the phosphate and hydroxyl group of sugar, with one such ester bond on either side
• DNA secondary structure


  • Double helix
  • Two strands of polynucleotides are antiparallel
  • Backbone is formed by the sugar-phosphate-sugar chain
  • Nitrogen bases face inside and A-T, G-C base pair
• DNA has more than a dozen forms named after English alphabets with unique structural features
• Metabolism


  All the chemical reactions constantly occurring in living organisms, where biomolecules are broken down and made
• Majority of metabolic reactions are linked in metabolic pathways, similar to automobile traffic in a city
• Every chemical reaction in living systems is a catalysed reaction, with enzymes as the catalysts
• Anabolic pathways


  Metabolic pathways that lead to more complex structures from simpler ones, consuming energy
• Catabolic pathways


  Metabolic pathways that lead to simpler structures from complex ones, releasing energy
• The most important form of energy currency in living systems is the bond energy in adenosine triphosphate (ATP)
• Living organisms exist in a steady-state characterised by concentrations of biomolecules, which are in a metabolic flux
• Living state is a non-equilibrium steady-state, maintained by constant energy input through metabolism
• Physical change


  Change in shape without breaking of bonds
• Chemical reaction


  Bonds are broken and new bonds are formed during transformation
• Rate of a physical or chemical process refers to the amount of product formed per unit time
• Catalysed reactions proceed at rates vastly higher than uncatalysed ones
• A multistep chemical reaction, where each step is catalysed by the same enzyme complex or different enzymes, is called a metabolic pathway
• Metabolic pathways


  • Glucose to pyruvic acid
  • Glucose to lactic acid in skeletal muscle
  • Glucose to ethanol in yeast fermentation