Introduction to METABOLISM
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Transcript of Introduction to METABOLISM
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Introduction to Introduction to METABOLISMMETABOLISM
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MetabolismMetabolismis the sum of all chemical changes occurring in a cell , tissue or the bodyIt is composed of pathwayspathways
PathwayPathwayis a multistep sequence of reactions is a multistep sequence of reactions in which the product of one reaction serves as the substrate of the subsequent in which the product of one reaction serves as the substrate of the subsequent reactionreactionEach reaction is catalyzed by a specific enzyme (may be with help of a coenzyme)Each reaction is catalyzed by a specific enzyme (may be with help of a coenzyme) A B C D E F G 1 2 3 4 5 6 Different pathways can intersectintersect forming a network of chemical reactions. K T A B C D E Pathways can be classified as either : L U cataboliccatabolic (degredative) or anabolicanabolic (synthetic) M V
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Glycolysis, an example of a metabolic pathway
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Metabolic mapMetabolic mapis a map that shows components of a pathways of metabolism It is useful in tracing connections between pathways
Example of aExample of a metabolic mapmetabolic map
metabolic map ofmetabolic map of intermediary
metabolism
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Catabolic ReactionsCatabolic Reactions
• Catabolic reactions break down complex molecules such as proteins, polysaccharides and lipids to few simple molecules• Serve to: yield energy in the form yield energy in the form of ATP of ATP from the degradation of energy- rich fuel molecules Allow molecules in the diet (or nutrient molecules stored in the cells) to be converted into building blocks building blocks needed for the synthesis of complex molecules
Catabolic & Anabolic ReactionsCatabolic & Anabolic Reactions
Anabolic ReactionsAnabolic Reactions
•Anabolic pathways form complex end products from simple precursors i.e. synthesis of glycogen from glucose & proteins from amino acids
• Requires energy Requires energy provided by breakdown of ATP to ADP & Pi
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ANABOLIC CATABOLIC
Biosynthetic Degradative
Reductive Oxidative
Energy Required Energy Liberated
Diverging Converging
Decomposition of large complex molecules into small molecules
large complex organic molecules are constructed from small molecules
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Catabolism
Many Few
Anabolism Few Many(converging)
(diverging)
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Nutrients Carbohydrates Fats Proteins
End products H2O, CO2, NH3
Catabolism(oxidative, exergonicexergonic)
Macromolecules Proteins Polysaccharides Lipids Nucleic acids
Precursor Molecules Amino acids Sugars Fatty acids Nitrogenous bases
Anabolism (reductive,
endergonicendergonic)
Chemical energy
ATPNADPH
NADPH
NADPH
GTP
ATP
ATP
NADH
Catabolism and anabolism are always related.
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Amphibolic PathwayAmphibolic Pathway
Amphi = Dual, amphibolic: dual pathwayAmphi = Dual, amphibolic: dual pathway
For example,For 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 acids
Therefore, Krebs cycle is amphibolic
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Stages of CatabolismStages of Catabolism
• Citric acid cycle Citric acid cycle produces NADH & FADH2
• Electrons flow from NADH & FADH2 in the mitochondria (electron transport electron transport chainchain) generates energy in the form of ATP (oxidative phosphorylationoxidative phosphorylation).
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Adenosine triphosphate Adenosine triphosphate ATPATP
(carrier of energy)
ATP ADP + Pi
ADP AMP + PiPi Pi Pi
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MitochondriaMitochondria
BATTERY OF THE CELLBATTERY OF THE CELL
site for generating ATPsite for generating ATP
Through Through
Electron Transport Chain Electron Transport Chain
& &
Oxidative PhosphorylationOxidative Phosphorylation
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In Electron Transport Chain Electron Transport Chain in the mitochondria
• Flow of electrons from NADH & FADH2 (through electron carriers CoQ & cytochromes) to oxygen yields energy • This energy is used for phosphorylation of ADP to ATP (phosphorylationphosphorylation)
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Flow of electrons
NADH
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Oxidative Phosphorylation (in mitochondria)Oxidative Phosphorylation (in mitochondria)
OxidationOxidation: electron flow in electron transport chain (with production of energy)
PhosphorylationPhosphorylation: phosphorylation of ADP to ATP
PHOSPHORYLATIOPHOSPHORYLATION
OXIDATION
NADH
ATPATP
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Diet Carbohydrates Glycogen (liver & Sk. Ms.)Diet Carbohydrates Glycogen (liver & Sk. Ms.)
Glucose Glucose
GLYCOLYSIS (in cytoplasm)
Lactate Pyruvate
in mitochondria
Acetyl CoA Citric Acid Cycle (in mitochondria)
NADH & FADH2
Electron transport chain (flow of electrons)
Formation of ATPATP(oxidative phosphorylation)
CATABOLISM OF CATABOLISM OF CARBOHYDRATESCARBOHYDRATES
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TriglyceridesTriglycerides
Fatty acids
Acetyl CoA
Citric acid cycle
ATPATPEnergy
Lipid CatabolismLipid Catabolism
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amino group ((-ketoacid)-ketoacid) (nitrogen) (carbon skeleton)
incorporated into other excreted catabolised synthesisCompounds of other compounds (e.g. urea) acetyl CoA
Citric Acid Cycle ATP ATP (energy)
Protein Amino Acid
Protein CatabolismProtein Catabolism
DEAMINATION