Biology XI: 9 Biomolecules (4 Metabolism)

Metabolism The Living State Living state is a non-equilibrium steady state to be able to perform work. System at equilibrium cannot perform work. Therefore, life processes occurring in an individual are constant efforts to avoid equilibrium state. Avoiding equilibrium state requires input of energy provided by metabolism. Hence, without metabolism, living state is not possible. The living organisms exist in steady state characterized by the concentration of biomolecules in their body and the steady state is a non-equilibrium state. Concept of metabolism All biomolecules present in body have a turnover. Turnover of biomolecules - They are constantly being converted to some other biomolecules and are made from some other biomolecules. Metabolism − All the chemical reactions that are involved in making or breaking of biomolecules Usually the metabolic reactions are interlinked and constitute a metabolic pathway whose flow may be linear or circular. This metabolite flow is known as dynamic state of body constituents. The metabolic reactions are always catalysed. The catalysts that enhance the rate of metabolic reactions are called enzymes. Example of metabolic reaction − reactions involved in glycolysis and Kreb’s cycle Metabolic Basis for Living Metabolic reactions are of two types − anabolic and catabolic   Anabolic Pathways Catabolic Pathways Biosynthetic pathways Formation of complex structure from simpler structures Involves consumption of energy Example − assembly of protein from amino acid Degradation pathways Formation of simpler structures from a complex structure Involves release of energy Example − glycolysis (glucose − Lactic acid) ATP (Adenosine triphosphate) − Energy currency in living systems is the bond energy stored in ATP. Primary and Secondary Metabolites Primary Metabolites − Intermediates or products of metabolism directly involved in growth, development, and reproductionExample − fatty acids, amino acids, etc. Secondary Metabolites − Intermediates or products of metabolism not involved directly in growth, development, and reproductionExample − Pigments such as carotenoids, toxins, drugs, and essential oils The roles of secondary metabolites are not directly identifiable. Some of them act as things for human utility such as rubber, pigments, spices, drugs, etc., while some others may have ecological importance.Some Secondary metabolites Pigments − Carotenoids, Anthocyanines Alkaloids − Morphine, Codeine Terpenoids − Mono-, Di-terpenes Essential oils − Lemon grass oil Toxins − Ricin Lectins − Concanavalin A