Metabolism is many coordinated chemical reactions occurring within a cell of an organism to sustain life (Berg et al. 2006). Obtaining nutrients, generating wastes, growing, reproducing, adapting to different environments are all chemical processes that occur in a human body to maintain a living state (Deborah, 2009). Many specific enzymes catalyse different chemical reactions in a metabolic pathway. Metabolic pathways are irreversible however; the reaction can be reversed by another pathway or an enzyme (Berg et al. 2006). For example, the glycolytic pathway can be reversed by gluconeogenesis.
Metabolic pathways can be separated into catabolic, anabolic and amphibolic reactions. Catabolism breaks down complex molecules like proteins and lipids into smaller and simpler molecules like amino acids and fatty acids; this reaction releases chemical energy, adenosine tri-phosphate (ATP) and reduced electron carriers NADH, NADPH and FADH2 (David
Daniell Cell: Construction and Working
JOHN FREDRRIC DANIELL, a British chemist