Introduction to METABOLISM

1. Introduction to METABOLISM

2. Metabolism is the sum of all chemical changes occurring in a cell , tissue or the body It is composed of pathways Pathway is a multistep sequence of reactions in which the product of one reaction serves as the substrate of the subsequent reaction 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 intersectforming a network of chemical reactions. K T A B C D E Pathways can be classified as either : L U catabolic (degredative) or anabolic (synthetic) M V

3. Glycolysis, an example of a metabolic pathway

4. Metabolic map is a map that shows components of a pathways of metabolism It is useful in tracing connections between pathways metabolic map of intermediary metabolism Example of a metabolic map

5. Catabolic & Anabolic Reactions • Catabolic Reactions • Catabolic reactions break down complex molecules such as proteins, polysaccharides and lipids to few simple molecules • Serve to: • yield energy in the form • 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 • needed for the synthesis • of complex molecules • Anabolic Reactions • Anabolic pathways • form complex end • products from simple • precursors • i.e. synthesis of • glycogen from glucose • & proteins from amino • acids • Requires energy • provided by • breakdown • of ATP to ADP & Pi

6. ANABOLIC CATABOLIC large complex organic molecules are constructed from small molecules Decomposition of large complex molecules into smallmolecules Degradative Biosynthetic Reductive Oxidative Energy Required Energy Liberated Diverging Converging

7. Catabolism Anabolism (diverging) (converging) Few Many Many Few

8. Macromolecules Proteins Polysaccharides Lipids Nucleic acids Nutrients Carbohydrates Fats Proteins GTP ATP NADPH Catabolism(oxidative, exergonic) Anabolism (reductive, endergonic) NADPH Chemical energy NADPH NADH ATP ATP Precursor Molecules Amino acids Sugars Fatty acids Nitrogenous bases End products H2O, CO2, NH3 Catabolism and anabolism are always related.

9. Amphibolic Pathway Amphi = Dual, amphibolic: dual pathway 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

10. Stages of Catabolism • Citric acid cycle produces NADH & FADH2 • Electrons flow from NADH & FADH2 in the mitochondria (electron transport • chain) generates energy in the form of ATP (oxidative phosphorylation).

12. Adenosine triphosphate ATP (carrier of energy) ATP ADP + Pi ADP AMP + Pi Pi Pi Pi

13. Mitochondria BATTERY OF THE CELL site for generating ATP Through Electron Transport Chain & Oxidative Phosphorylation

14. InElectron 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 • (phosphorylation)

15. Flow of electrons NADH

16. ATP PHOSPHORYLATION OXIDATION NADH Oxidative Phosphorylation (in mitochondria) Oxidation: electron flow in electron transport chain (with production of energy) Phosphorylation: phosphorylation of ADP to ATP

17. Diet Carbohydrates Glycogen (liver & Sk. Ms.) 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 ATP (oxidative phosphorylation) CATABOLISM OF CARBOHYDRATES

18. Triglycerides Fatty acids Acetyl CoA Citric acid cycle ATP Energy Lipid Catabolism

19. Protein Catabolism Protein Amino Acid amino group (a-ketoacid) (nitrogen) (carbon skeleton) incorporated into other excreted catabolisedsynthesis Compounds of other compounds (e.g. urea) acetyl CoA Citric Acid Cycle ATP (energy) DEAMINATION