Metabolic pathway By Noah Philemon

1. METABOLIC PATHWAY By Mbingamno, A

2. INTRODUCTION • All living organisms need energy to grow and reproduce, maintain their structures, and respond to their environments; • Metabolism is the set of the processes that makes energy available for cellular processes. • Metabolism is a combination of chemical reactions that are spontaneous and release energy and chemical reactions that are non-spontaneous and require energy in order to proceed.

3. Cont. • Living organisms must take in energy via food, nutrients, or sunlight in order to carry out cellular processes. • The transport, synthesis, and breakdown of nutrients and molecules in a cell require the use of energy. • Metabolism: Is the complete set of chemical reactions that occur in living cells

4. Energy and Metabolism • All living organisms need energy to grow and reproduce, maintain their structures, and respond to their environments. • Metabolism is the set of life-sustaining chemical processes that enables organisms transform the chemical energy stored in molecules into energy that can be used for cellular processes.

5. Cont. • Animals consume food to replenish energy; their metabolism breaks down the carbohydrates, lipids, and proteins to provide chemical energy for these processes. • Plants convert light energy from the sun into chemical energy stored in molecules during the process of photosynthesis.

6. Metabolic Pathway • A metabolic pathway is a series of chemical reactions in a cell that build and breakdown molecules for cellular processes. Or • Is a step-by-step series of interconnected biochemical reactions that convert a substrate molecule(s) through a series of metabolic intermediates, eventually yielding a final product(s)

7. Cont. • Because almost all metabolic reactions take place non-spontaneously, proteins called enzymes help facilitate those chemical reactions. • All organisms require energy to complete tasks;

8. Cont. • The processes of making and breaking down carbohydrate molecules illustrate two types of metabolic pathways.

9. TYPES OF METABOLIC PATHWAYS • There are two types A. Anabolic pathways (Anabolism) are those that require energy to synthesize larger molecules. OR Requires energy and builds molecules

10. Cont. • Anabolic pathways require an input of energy to synthesize complex molecules from simpler ones. • Examples of an anabolic pathway is the synthesis of sugar from CO2, synthesis of large proteins from amino acid and the synthesis of new DNA strands from nucleic acid.

11. Cont. • These processes are critical to the life of the cell, take place constantly, and demand energy provided by ATP and other high-energy molecules like NADH and NADPH

12. Catabolic Pathways • Catabolic pathways are those that generate energy by breaking down larger molecules. • Some catabolic pathways can capture that energy to produce ATP, the molecule used to power all cellular processes.

13. Cont. • Other energy-storing molecules, such as lipids, are also broken down through similar catabolic reactions to release energy ( make ATP). • Both types of pathways are required for maintaining the cell’s energy balance.

14. Cont.

15. Importance of Enzymes • Chemical reactions in metabolic pathways rarely take place spontaneously. Each reaction step is facilitated, or catalyzed, by a protein called an enzyme. • Enzymes are important for catalyzing all types of biological reactions: those that require energy as well as those that release energy.

16. Cellular Metabolism • Every task performed by living organisms requires energy. Energy is needed to perform heavy labor and exercise. • For every action that requires energy, many chemical reactions take place to provide chemical energy to the systems of the body, including muscles, nerves, heart, lungs, and brain.

17. Cont. • The living cells of every organism constantly use energy to survive and grow. Cells break down complex carbohydrates into simple sugars that the cell can use for energy. • Molecules can be modified and transported around the cell or may be distributed to the entire organism. • Energy is required for both the synthesis and breakdown of molecules

18. Metabolism of Carbohydrates • Organisms break down carbohydrates to produce energy for cellular processes, and photosynthetic plants produce carbohydrates. • Carbohydrates are one of the major forms of energy for animals and plants. Plants build carbohydrates using light energy from the sun (during the process of photosynthesis), while animals eat plants or other animals to obtain carbohydrates.

19. Plants store carbohydrates in long polysaccharides chains called starch, while animals store carbohydrates as the molecule glycogen. • These large polysaccharides contain many chemical bonds and therefore store a lot of chemical energy. • When these molecules are broken down during metabolism, the energy in the chemical bonds is released and can be harnessed for cellular processes.

20. Energy Production from Carbohydrates (Cellular Respiration) • The metabolism of any monosaccharide (simple sugar) can produce energy for the cell to use. • Excess carbohydrates are stored as starch in plants and as glycogen in animals, ready for metabolism if the energy demands of the organism suddenly increase.

21. Cont. • When energy demands increase, carbohydrates are broken down into constituent monosaccharides, which are then distributed to all the living cells of an organism. • Glucose (C6H12O6) is a common example of the monosaccharides used for energy production.

22. Cont. • Inside the cell, each sugar molecule is broken down through a complex series of chemical reactions. As chemical energy is released from the bonds in the monosaccharide, it is harnessed to synthesize high-energy adenosine triphosphate (ATP) molecules. • ATP is the primary energy of all cells. cells use molecules of ATP to perform immediate work and power chemical reactions.

23. Cont. • The breakdown of glucose during metabolism is called cellular respiration can be described by the equation: • C6H12O6+6O2→6CO2+6H2O+energy

24. GLYCOLSIS • Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. • Is a series of reactions that extract energy from glucose by splitting it into two three-carbon molecules called pyruvates.

25. Cont. • Glycolysis is the sequence of 10 enzyme catalyzed reactions that converts glucose into pyruvate with the simultaneous production of ATP. • The overall reaction of glycolysis is represented simply as: • C6H12O6 + 2 NAD+ + 2 ADP + 2 P —> 2 pyruvic acid, (CH3(C=O)COOH + 2 ATP + 2 NADH + 2 H+

26. Steps of Glycolysis • Glycolysis takes place in the cytosol of a cell, and it can be broken down into two main phases: the energy-requiring phase and the energy-releasing phase.

27. Cont. • Glycolysis involves various distinct reactions that convert glucose into pyruvate. • Glucose is a six- membered ring molecule found in the blood as a result of the breakdown of carbohydrates into sugars. • It enters cells through specific transporter proteins that move it from outside the cell into the cell's cytosol. • All of the glycolytic enzymes are found in the cytosol.

28. Energy-requiring(glucose activation) Phase: • In this phase, two molecules of ATP are invested and the hexose chain is cleaved into two triose phosphates. • Phosphorylation of glucose and it’s conversion to glyceraldehyde-3-phosphate take place. • The preparatory phase involve steps 1, 2, 3, 4 and 5.

29. Energy-releasing (extraction) phase. • The conversion of glyceraldehyde-3-phosphate to pyruvate and the coupled formation of ATP take place.  • Because Glucose is split to yield two molecules of Glyceraldehyde-3-phosphate, each step in the payoff phase occurs twice per molecule of glucose. • The steps after 5 constitute payoff phase

30. Step 1 • Conversion of glucose into glucose-6-phosphate. The enzyme that catalyzes this reaction is hexokinase. • The glucose ring is phosphorylated. Phosphorylation is the process of adding a phosphate group to a molecule derived from ATP.

31. Cont.

32. Step 2 • Rearrangement of glucose 6-phosphate (G6P) into fructose 6-phosphate (F6P) by glucose phosphate isomerase (PhosphoglucoseIsomerase). • This reaction involves an isomerization reaction

33. Cont.

34. Step 3 • Phosphofructokinase, with magnesium as a cofactor, changes fructose 6-phosphate into fructose 1,6-bisphosphate.

35. Cont.

36. Step 4 • Aldolaseenzyme splits fructose 1, 6-bisphosphate into two sugars that are isomers of each other (dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP)).

37. Cont.

38. Step 5 • The enzyme triophosphateisomerase rapidly inter- converts the molecules dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP).

39. Step 6: • Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) dehydrogenates and adds an inorganic phosphate to glyceraldehyde 3-phosphate, producing 1,3-bisphosphoglycerate. • That is, two main events take place: • 1) glyceraldehyde-3-phosphate is oxidized by the coenzyme NAD; • 2) The molecule is phosphorylated by the addition of a free phosphate group. (glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-enzymes).

40. Cont.

41. Step 7 • Phosphoglyceratekinase transfers a phosphate group from 1,3-bisphosphoglycerate to ADP to form ATP and 3-phosphoglycerate.

42. Cont.

43. Step 8: • The enzyme phosphoglyceromutaserelocates the P from 3- phosphoglycerate from the 3rd carbon to the 2nd carbon to form 2-phosphoglycerate. • Rearrangement of the position of the phosphate group on the 3 phosphoglycerate molecule, making 2 phosphoglycerate. • Amutase is an enzyme that catalyzes the transfer of a functional group from one position on a molecule to another.

44. Cont.

45. Step 9: • The enzyme enolase removes a molecule of water from 2-phosphoglycerate to form phosphoenol pyruvic acid (PEP). • Involves the conversion of 2 phosphoglycerate to phosphoenolpyruvate (PEP). • Enolase works by removing a water group, or dehydrating the 2 phosphoglycerate.

46. Cont.

47. Step 10 • The final step of glycolysis. • Conversion of phosphoenol pyruvate into pyruvate with the help of the enzyme pyruvate kinase. • The phosphate group attached to the 2' carbon of the PEP is transferred to a molecule of ADP, yielding ATP. • Two molecules of PEP, generate 2 ATP molecules.

48. Cont.

49. Cont… • Net inputs of glycolysis • Glucose + 2NAD+ +2ATP + 4ADP + 2Pi • The outputs from glycolysis • 2 Pyruvate + 2 NADH + 2ADP + 4 ATP

50. Net ATP gain • 2 ATP molecules are used. • A total of 4 ATP molecules produced. • A net total of 2 ATP molecules produced. Net gain of glycolysis • 2 ATP + 2NADH + 2 Pyruvate