HBG 4 ( Introduction of Metabolism)

• Assoc Prof Dr Ho Kok Lian is from the Dept of Pathology, UPM.
• Nutritional requirement and energy for metabolism are important aspects of living organisms.
• Metabolism consists of two contrasting processes: catabolism, where biomolecules are broken down to small precursors, releasing energy, and anabolism, where complex biomolecules are synthesised from simpler components, requiring energy.
• Major metabolic pathways in the body include amphibolic pathways, which involve both catabolic and anabolic processes.
• ATP, or adenosine triphosphate, is the energy currency of the cell.
• Coupling reactions involve the hydrolysis and regeneration of ATP.
• Coenzyme A plays crucial roles in various structures and functions.
• Autotrophs use CO2 as their sole carbon source and biosynthesise their own food.
• Heterotrophs obtain energy from the oxidation of food or organic compounds such as CHO, prot, and lipid.
• Animals, humans, and most microorganisms are examples of heterotrophs.
• Metabolism refers to the cellular processes through which living organisms (including every single cell) acquire and use energy sources to carry out various functions to sustain life.
• Metabolic pathways are series of connected enzymatic reactions.
• Energy-poor end products include H2O, CO2, NH3, and CATABOLISM is oxidative, exergonic.
• Metabolites are all molecules involved in metabolism, including reactants, intermediates, and products.
• Some central pathways of intermediary metabolism, such as the TCA cycle and glycolytic pathways, have dual purposes both in catabolism and anabolism.
• Differences allow regulation of catabolic and anabolic pathways separately.
• Reducing power equivalents and energy include NADPH, NADH, FADH2, GTP, and ATP.
• Biosynthesis is the construction of complex metabolites from smaller and simpler precursors, requiring precursors, energy, and reducing power from catabolic pathways.
• These pathways are said to be amphibolic.
• Metabolic pathways are catabolic pathways plus anabolic pathways.
• Energy-rich nutrients include carbohydrates, lipids, and proteins.
• Biochemical reactions involve complex metabolites being broken down into simpler and smaller products, providing precursors, energy, and reducing power for anabolic pathways.
• Anabolism is reductive, endergonic.
• Amplibolic pathways for catabolism and anabolism may differ, although some steps may be the same, for example, see glycolysis.
• Metabolic pathways in the cells include the pentose phosphate pathway, nucleic acids (DNA, RNA), amino acids, proteins, glucose, pyruvate, acetyl CoA, glycogen/CHO, TCA cycle, CO2, FADH2, NADH, ATP, and Fatty acids, cholesterol.
• In the form of free energy, ATP is required to perform various ATP-dependent reactions such as muscle contraction and anabolic mechanism.
• Phosphoanhydride bonds are "high energy bonds" due to repulsion of negatively charged phosphate groups.
• ATP can also be hydrolysed/regenerated by coupling reactions.
• Exergonic reactions release energy, while endergonic reactions require energy.
• ATP is produced by substrate level phosphorylation.
• Energy is synthesised in the form of ATP, which is the "energy currency" of cells/tissues.
• Pyrophosphate (Pi) is transferred to other molecules by coupling reactions, requiring energy.
• Overall DG in kJ/mol.
• Gluconeogenesis is the process of generating glucose from non-carbohydrate sources.
• NADH and FADH2 are generated during catabolic reactions such as glycolysis and TCA cycle.
• High energy phosphate compounds are hydrolysed by specific enzyme.
• Std free energy DG (kJ/mol) for various compounds are: Phosphoenolpyruvate (PEP) - 61.9, 1,3 - bisphosphoglycerate - 49.4, Acetyl phosphate - 43.1, Phosphocreatine - 43.1, ATP (® ADP + Pi) - 30.5, Glucose - 1 - phosphate - 20.9, PPi - 19.2, Fructose - 6 - phosphate - 13.8, Glucose - 6 - phosphate - 13.8, Glycerol - 3 - phosphate - 9.2.
• Glucose, Pyruvate, and Glycolysis are part of the energy synthesis process.
• The overall DG must be negative for the reaction to take place.
• ATP is generated during Glycolysis and Oxidative Phosphorylation through oxidation of NADH (reduced NAD+) or FADH2 (reduced FAD+).