Metabolism Lecture Notes PDF

Lecture No.1 Metabolism Metabolism is the process through which living systems obtain and use free energy to carry out functions. Metabolism requires highly coordinated cellular activity Metabolism performs 4 functions 1. Obtain energy for the cell....

Lecture No.1 Metabolism Metabolism is the process through which living systems obtain and use free energy to carry out functions. Metabolism requires highly coordinated cellular activity Metabolism performs 4 functions 1. Obtain energy for the cell. 2. Convert nutrients into macromolecules. 3. Assemble macromolecules into cellular structures. 4. Degrade macromolecules as required for biological function. Metabolism consists of catabolism and anabolism. Catabolism is the degradation pathways to recover components and energy from biomolecules such as nucleotides, proteins, lipids and polysaccharides. The process generates energy. Anabolism is the biosynthesis of biomolecules such as nucleotides, proteins, lipids and polysaccharides from simple precursor molecules. This process requires energy. Biomolecules are composed predominantly of carbon, hydrogen, oxygen and nitrogen. Metabolic Pathways Enzymes are the basic units of metabolism. The substrates of these enzymes are called metabolites. A metabolic pathway is a series of connected enzymatic reactions that produce a specific product. Metabolic pathways consist of sequential steps. There are more than 2,000 metabolic reactions, each catalyzed by a distinct enzyme. The enzymes may be physically separate requiring the intermediate metabolites to diffuse from one active site to the next or enzymes may form a multienzyme complex where the intermediate metabolites are passed directly from one active site to the next. Some pathways reside within membranes. In this case the enzyme and the substrates diffuse in the two dimensions of the bilipid membrane.  Metabolic pathways The catabolic and anabolic pathways are related. Catabolism Complex metabolites are degraded into simpler products such as acetyl units linked to coenzyme A. The degradation process releases free energy. The free energy is conserved by the reduction of NADP+ NADPH or by coupling exergonic reactions ( a metabolic or chemical process accompanied by the release of energy) to ATP synthesis. Anabolism Complex biomolecules are synthesized from simple precursors. This process is endergonic (a metabolic or chemical process accompanied by or requiring the absorption of energy). This process requires the free energy of ATP hydrolysis, ATP ADP+ + Pi or NADH oxidation, NADH NAD+. The striking feature of anabolic pathways is that they begin with a few common metabolites as starting materials and diverge into a wide range of biomolecules. Diagram represents catabolism and anabolism