Intermediary metabolism

Intermediary metabolism

January 8, 2022

Metabolism is a highly coordinated cellular activity aimed at achieving the following goals:

  • Obtain chemical energy.
  • Convert nutrient molecules into the cell’s own characteristic molecules.
  • Degrade biomolecules

Metabolism, the sum of all the chemical transformations taking place in a cell or an organism, occurs through a series of enzyme-catalyzed reactions that constitute metabolic pathways. 

Each of the steps in a metabolic pathway brings about a specific chemical change

  • Removal or transfer or addition of a particular atom or functional group.
  • The precursor is converted into a product through a series of metabolic intermediates called metabolites.
  • The term intermediary metabolism is often applied to the combined activities of all the metabolic pathways that interconvert precursors, metabolites, and products of low molecular weight (generally, Mr  1,000).

Catabolism is the degradative pathways of metabolism

  • Organic nutrients (carbohydrates, fats, and proteins) are converted into smaller, simpler end products (such as lactic acid, CO2, NH3).
  • Released energy
  • ATP
  • Reduced electron carriers (NADH, NADPH, and FADH2);
  • Rest is lost as heat

Anabolism, also refers to the biosynthesis pathways, 

  • In which small, simple precursors are built up into larger and more complex  molecules, including lipids, polysaccharides, proteins, and nucleic acids.
  • Anabolic reactions require an input of energy
  • Mostly ATP and occasionally GTP, CTP and UTP
  • Reducing power of NADH, NADPH, and FADH2


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