2 Objectives Understand the concept of metabolic pathway Identify types & characters of metabolic pathways- anabolic and catabolicIdentify ATP as the energy currency of cellsUnderstand the transport of major metabolic fuel- Glucose
3 MetabolismAll the chemical reactions taking place inside a cell are collectively known as METABOLISM
4 MetabolismMetabolic Pathways are chemical reactions organized in multisteps sequences where:The product of one reaction of the pathway serves as substrate of the subsequent reactionMost pathways can be classified as anabolic (synthetic) or catabolic (degenerative)Integrated pathways= Metabolism
6 Basic functions of metabolism To obtain energy from fuel moleculesTo convert nutrients into precursors of cellular components.3. To assemble precursors utilizing energy into cellular components.
7 ANABOLIC CATABOLIC Biosynthetic Degradative Reductive Oxidative large complex organic molecules are constructed from small moleculesDecomposition of large complex molecules into small moleculesBiosyntheticDegradativeReductiveOxidativeEnergy RequiredEnergy LiberatedDivergingConverging
12 Amphibolic Pathway For example, Amphi = Dual, amphibolic: dual pathwayFor example,Krebs cycle is mainly a catabolic cycle, but with some anabolic features,e.g., part of Krebs cycle is used for the synthesis of glucose from amino acidsTherefore, Krebs cycle is amphibolic12
13 Metabolic MapDifferent pathways can intersect, forming an integrated and purposeful network of chemical reactions “The Metabolic Map”
15 Chemical energyATP - energy currency. It serves as the driving force for nearly all biochemical processesNADH,NADPH - reducing power.NADH for oxidation and energy yielding.NADPH for biosynthetic processes
16 ATP is the energy currency of the cell ATP + H2O ADP +PiThe free energy liberated in the hydrolysis of ATP is used to drive the endergonic reactionsATP is formed from ADP and Pi when fuel molecules are oxidizedThis ATP-ADP cycle is the fundamental mode of energy exchange in biological systems
22 Intracellular Regulation Imp. for moment-to-moment regulation of metabolism which elicit rapid responses by:availability of substrateproduct inhibition oralteration in the levels of allosteric activators or inhibitors
23 Intercellular Regulation Provides long-range integration of metabolismUsually is slower than intracellular signals, it is done by : surface to surfacethe most important ischemical signaling by hormones or neurotransmittersThis results in the production of second messengers
24 Metabolic FuelCarbohydrates & lipids (mainly) and proteins (little extent) are used for energy productionThese are- glucose, fatty acids and amino acidsGlucose is the major metabolic fuel of most tissues
25 Glucose Transport Na+-Monosaccharide Cotransporter: Against concentration gradientEnergy dependentCarrier-mediatedCoupled to Na+ transportSmall intestine, renal tubules & choroid plexusNa+-Independent Facilitated Diffusion:With concentration gradientEnergy IndependentGlucose Transporters (GLUT 1-14)
27 Glucose Transporters Tissue-specific expression pattern GLUT-1 RBCs and brainGLUT-2 Liver, kidney & pancreasGLUT-3 NeuronsGLUT-4 Adipose tissue & skeletal muscleGLUT-5 Small intestine & testesGLUT-7 Liver (ER-membrane)Functions:GLUT-1, 3 & 4 Glucose uptake from bloodGLUT-2 Blood & cells (either direction)GLUT-5 Fructose transport
28 Take Home MessageMetabolism is the sum of all biochemical pathways that occur inside the cells.A metabolic pathway is a multistep sequences of enzyme-catalyzed reactions.
29 Catabolism is a convergent process that provides energy to cells in the form of ATP. Anabolism is a divergent process that consumes energy for the synthesis of complex molecules.Metabolic pathways are tightly regulated and highly integrated.
30 ATP is the energy currency of the cells Glucose is transported in/out of the cells by:Energy-dependent active transportEnergy-independent facilitated transport