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Introduction to Metabolism

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Presentation on theme: "Introduction to Metabolism"— Presentation transcript:

1 Introduction to Metabolism

2 Objectives Understand the concept of metabolic pathway
Identify types & characters of metabolic pathways- anabolic and catabolic Identify ATP as the energy currency of cells Understand the transport of major metabolic fuel- Glucose

3 Metabolism All the chemical reactions taking place inside a cell are collectively known as METABOLISM

4 Metabolism Metabolic Pathways are chemical reactions organized in multisteps sequences where: The product of one reaction of the pathway serves as substrate of the subsequent reaction Most pathways can be classified as anabolic (synthetic) or catabolic (degenerative) Integrated pathways= Metabolism

5 Glycolysis, an example of a metabolic pathway

6 Basic functions of metabolism
To obtain energy from fuel molecules To 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 molecules Decomposition of large complex molecules into small molecules Biosynthetic Degradative Reductive Oxidative Energy Required Energy Liberated Diverging Converging

8 Catabolism Anabolism (diverging) (converging) Few Many Many Few

9 Catabolic Pathway

10 Anabolic Pathway Combine small moles as a.a. to form complex as ptn
It is a divergent process w needs ATP (endergonic) & reducing power (mostly NADPH)

11 Catabolism(oxidative, exergonic) Anabolism (reductive, endergonic)
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.

12 Amphibolic Pathway For example,
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 12

13 Metabolic Map Different pathways can intersect, forming an integrated and purposeful network of chemical reactions “The Metabolic Map”


15 Chemical energy ATP - energy currency. It serves as the driving force for nearly all biochemical processes NADH,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 +Pi The free energy liberated in the hydrolysis of ATP is used to drive the endergonic reactions ATP is formed from ADP and Pi when fuel molecules are oxidized This ATP-ADP cycle is the fundamental mode of energy exchange in biological systems

17 Adenosine Triphosphate (ATP)
Δ Gº -7.3 kcal/mol/bond

18 Oxidation-Reduction in Metabolism
E-rich compounds e.g., E-rich reduced coenzymes Oxidation ETC 18

19 Oxidation/Reduction Oxidation: Loss of hydrogen Loss of electrons
Gain of hydrogen Gain of electrons


21 Metabolism Regulation

22 Intracellular Regulation
Imp. for moment-to-moment regulation of metabolism which elicit rapid responses by: availability of substrate product inhibition or alteration in the levels of allosteric activators or inhibitors

23 Intercellular Regulation
Provides long-range integration of metabolism Usually is slower than intracellular signals, it is done by : surface to surface the most important is chemical signaling by hormones or neurotransmitters This results in the production of second messengers

24 Metabolic Fuel Carbohydrates & lipids (mainly) and proteins (little extent) are used for energy production These are- glucose, fatty acids and amino acids Glucose is the major metabolic fuel of most tissues

25 Glucose Transport Na+-Monosaccharide Cotransporter:
Against concentration gradient Energy dependent Carrier-mediated Coupled to Na+ transport Small intestine, renal tubules & choroid plexus Na+-Independent Facilitated Diffusion: With concentration gradient Energy Independent Glucose Transporters (GLUT 1-14)

26 Glucose Transport: Facilitated Diffusion

27 Glucose Transporters Tissue-specific expression pattern
GLUT-1 RBCs and brain GLUT-2 Liver, kidney & pancreas GLUT-3 Neurons GLUT-4 Adipose tissue & skeletal muscle GLUT-5 Small intestine & testes GLUT-7 Liver (ER-membrane) Functions: GLUT-1, 3 & 4 Glucose uptake from blood GLUT-2 Blood & cells (either direction) GLUT-5 Fructose transport

28 Take Home Message Metabolism 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 transport Energy-independent facilitated transport

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