carbohydrates metabolism in prokaryotes ppt.pptx

Prokaryotes metabolize carbohydrates through glycogen synthesis (ADP-Glc pyrophosphorylase & glycogen synthase) and breakdown (glycogen phosphorylase), regulated by allosteric effectors.

1. Carbohydrates metabolism in prokaryotes

2. Contents: Introduction Glycolysis Krebs cycle Electron transport chain Anaerobic respiration Pentose phosphate pathways Gluconeogenesis Glycogen synthesis and storage Regulation of carbohydrate metabolism

3. INTRODUCTION: Metabolism: Different types of cells are performing specific functions. To perform various functions a cell need energy. This energy is provided by the chemical reactions. The sum of all the chemical reactions going on within the cells is known as metabolism . Two types of metabolism: Catabolism: Reactions which break down complex molecules into simpler molecules are called catabolism. Anabolism : Reactions which build complex molecules from simpler molecules are called anabolism.

4. Intro… Carbohydrates metabolism in prokaryotes: Carbohydrate metabolism in prokaryotes involves various processes like glycolysis, fermentation or respiration, the pentose phosphate pathway, the gluconeogenesis, glycogen synthesis and storage and regulation of carbohydrate metabolism. These pathways are crucial for energy production and providing building blocks for cellular processes in prokaryotes. Carbohydrates are the most abundant organic forms and high-grade energy sources on Earth .

5. Cont… The breakdown of glucose to obtain ATP can be summarized by the following equation: C6H12O6 + 6O2 = 6CO2 + 6H2O + 686 kcal/mol glucose. A variety of carbohydrates are utilized by prokaryotic organisms in subsistence and energy production. The most important carbohydrate is glucose, which has several possible fates. Aerobic organisms convert it to CO2 and H2O with the production of 38 ATP in a process known as cellular respiration.

6. Aerobic respiration: Glycolysis Glycolysis takes place in cytoplasm of the cell , outside the mitochondria. It occur both in anaerobic and aerobic respiration . A single molecule of glucose is broken down into two molecules of pyruvic acid , 2 ATP molecules and 2 NAD+ molecules are reduced to NADH . Glucose > 2 pyruvic acid+ 2 ATP + 2NADH

7. Steps of glycolysis: Glucose Phosphorylation: Glucose, a six-carbon sugar, is phosphorylated by ATP to form glucose-6-phosphate. This reaction is catalyzed by the enzyme hexokinase or glucokinase. Isomerization: Glucose-6-phosphate is converted into fructose-6-phosphate through an isomerization reaction catalyzed by the enzyme phosphoglucose isomerase. Phosphorylation of Fructose-6-Phosphate : Fructose-6-phosphate is phosphorylated by ATP to form fructose-1,6-bisphosphate. This reaction is catalyzed by the enzyme phosphofructokinase.

8. Cont… Cleavage: Fructose-1,6-bisphosphate is cleaved into two three-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). This reaction is catalyzed by the enzyme aldolase . Isomerization: Dihydroxyacetone phosphate (DHAP) is isomerized into another molecule of glyceraldehyde-3-phosphate (G3P) by the enzyme triose phosphate isomerase. This step ensures that all the carbon atoms from glucose are available in the same form for further metabolism. Oxidation and ATP Generation: Glyceraldehyde-3-phosphate (G3P) is oxidized by NAD+ to form 1,3-bisphosphoglycerate while NADH is produced. This reaction is catalyzed by the enzyme glyceraldehyde-3-phosphate dehydrogenase. Additionally, a phosphate group is transferred from 1,3-bisphosphoglycerate to ADP to form ATP. This reaction is catalyzed by phosphoglycerate kinase.

9. Cont… Substrate-level Phosphorylation: 1,3-bisphosphoglycerate is converted into 3-phosphoglycerate by the enzyme phosphoglycerate kinase. In this reaction, another ATP molecule is generated through substrate-level phosphorylation. Conversion of 3-Phosphoglycerate to 2-Phosphoglycerate: The enzyme phosphoglycerate mutase catalyzes the transfer of a phosphate group from the third carbon of 3-phosphoglycerate to the second carbon, forming 2-phosphoglycerate. Enolization and Dehydration: 2-phosphoglycerate undergoes Enolization to form phosphoenolpyruvate (PEP). In this process, a water molecule is removed. This reaction is catalyzed by the enzyme enolase.

10. Cont… Substrate-level Phosphorylation: Phosphoenolpyruvate (PEP) donates its phosphate group to ADP to form ATP and pyruvate. This reaction is catalyzed by the enzyme pyruvate kinase. At the end of glycolysis, one molecule of glucose is converted into two molecules of pyruvate, along with the net production of two molecules of ATP and two molecules of NADH.

11. Kreb cycle: The Krebs cycle (also known as the citric acid cycle or tricarboxylic acid cycle) is a series of chemical reactions that occur within the mitochondria of cells. It is a key process by which cells generate energy from the food they consume. Is a metabolic pathway that breaks down acetyl-CoA (derived from carbohydrates, fats, and proteins) to produce: Energy (in the form of ATP, NADH, and FADH2) Precursors for amino acid and cholesterol synthesis Consists of eight distinct steps, each catalyzed by a specific enzyme.

12. Cont… 1 . Acetyl-CoA enters the cycle 2. Citrate is formed (step 1) 3. Isomerization and oxidation reactions occur (steps 2-4) 4. Alpha-ketoglutarate is formed (step 5) 5. NADH and ATP are produced (steps 6-7) 6. Oxaloacetate is regenerated (step 8)

13. Electron transport chain: The electron transport chain (ETC) is a series of protein complexes located in the mitochondrial inner membrane. It plays a crucial role in cellular respiration, generating energy for the cell through the transfer of electrons. Functions: Transfers electrons from high-energy molecules (NADH, FADH2) to oxygen Generates a proton gradient across the mitochondrial membrane Drives ATP synthesis through chemiosmosis.

14. Cont… Components: 1. Complex I (NADH dehydrogenase) 2. Complex II (Succinate dehydrogenase) 3. Complex III (Cytochrome b-c1 complex) 4. Complex IV (Cytochrome c oxidase) 5. Coenzyme Q (CoQ) and cytochrome c (mobile electron carriers)

15. Cont… Process: 1 . Electrons from NADH and FADH2 are passed through the complexes 2. Protons are pumped across the membrane, creating a gradient 3. The gradient drives ATP synthesis through the enzyme ATP synthase 4. Oxygen is the final electron acceptor, reducing it to water.

16. Anaerobic respiration: Anaerobic respiration is a metabolic process that occurs in the absence of oxygen (O2). It is a mechanism used by cells to generate energy in the form of ATP (adenosine triphosphate) without using oxygen. This process is also called fermentation. Glucose is converted into energy (ATP) without the presence of oxygen. Lactic acid or ethanol and carbon dioxide are produced as byproducts.

17. Cont… Types of anaerobic respiration: Alcoholic fermentation: In alcoholic fermentation, pyruvic acid during glycolysis is converted into ethyl alcohol and Carbon Dioxide. It occur in yeast and some bacteria. Pyruvic acid → 2 Ethanol + 2 CO₂ + 2 ATP

18. Cont… Lactic acid fermentation: During vigorous exercise your heart and lung cannot provide enough oxygen to skeletal muscles quickly enough. When this happen muscles start to carry out anaerobic respiration and each pyruvic acid molecule is converted into lactic acid. Bacteria which convert milk to yogurt also produce lactic acid. Pyruvic acid → 2 Lactic Acid + 2 ATP

19. Pentose phosphate pathway

20. INTRODUCTION The pentose phosphate pathway (PPP) in prokaryotes is an essential metabolic pathway that operates in the cytoplasm. Alternative pathway for glucose oxidation. No ATP formation Produce NADPH and Ribose 5 phosphate . This pathway completes in 2 phases.

21. OXIDATIVE PATHWAY In this phase NADPH and Ribulose- 5 –phosphate are produced. NON-OXIDATIVE PATHWAY The non-oxidative phase involves the production of different sugar intermediates. Ribulose -5-Phosphate synthesize sugar intermediates in the presence of 3 enzymes. Enzymes are Epimerase Transaldolase Transketolase

22. Gluconeogenesis : INTRODUCTION Formation of glucose from non- carbohydrate sources is gluconeogenesis. Gluconeogenesis is the metabolic pathway that allows prokaryotic organisms, such as bacteria, to synthesize glucose from non-carbohydrate precursors. This process is essential for maintaining cellular energy levels and ensuring survival in environments where glucose is scarce.

23. NON-CARBOHYDRATE PRECURSORS Lactate Glycerol Glucogenic amino acids Propionyl CoA Pyruvate KEY ENZYMES Pyruvate carboxylase , Phosphoenol pyruvate carboxy kinase ( PEPCK ) Fructose -6-phosphatase, Glucose -6- phosphatase

24. Location Gluconeogenesis in prokaryotes, such as bacteria, occurs in the cytosol, which is the fluid component of the cytoplasm. Prokaryotes lack a true nucleus and other membrane-bound organelles, so gluconeogenesis occurs in the same compartment as glycolysis.

25. Overview Of Glycolysis and Gluconeogenesis Overview of glycolysis and gluconeogenesis pathways. Glycolysis (purple) consists of 10 reactions, leading to the production of pyruvate. Three steps are considered as rate-limiting, catalyzed by hexokinases or glucokinases, phosphofructokinase 1, and pyruvate kinase. Gluconeogenesis (blue) is the reversed steps of glycolysis, with four specific reactions catalyzed by glucose-6-phosphatase, fructose 1,6-bisphosphatase, phosphoenolpyruvate carboxykinase 1, and pyruvate carboxylase.

26. Physiological Significance and Applications Survival in Starvation Gluconeogenesis allows prokaryotes to synthesize glucose from non-carbohydrate sources, enabling them to survive periods of nutrient deprivation. Biotech Applications Understanding gluconeogenesis in prokaryotes has led to the development of genetically engineered bacteria for the production of pharmaceuticals. And biofuels.

27. Glycogen synthesis and storage Formation of glycogen from glucose known as GLYCOGENESIS. Glycogen synthesis and storage in prokaryotes, such as bacteria, is an important biological process that allows these organisms to store energy in the form of glycogen. Glycogen is a branched polysaccharide made up of glucose units and serves as a reserve of carbon and energy. Occurs in some prokaryotes such as bacteria e.g E.coli , Archaebacteria .

28. Pathway Of Glycogen Synthesis Activation of glucose Initiation of Glycogen Synthesis Elongation Branching Glycogen

29. Storage Glycogen is stored in the cytoplasm of prokaryotic cells as granules . These granules can vary in size and number depending on the species and environmental conditions. FUNCTIONS Energy storage Carbon and energy source during starvation or stress

30. Regulation Of Carbohydrates metabolism Prokaryotes regulate carbohydrate metabolism through allosteric regulation of enzyme activity, covalent modification of enzymes, transcriptional regulation of gene expression, and feedback inhibition by metabolic end products.

31. Allosteric regulation : Enzyme activity is modulated by binding of effectors, such as metabolites or ions, to specific sites. Example : Glucose binding to hexokinase enzyme, increasing its activity to phosphorylate glucose. Covalent modification : Enzymes are activated or inhibited by covalent attachment or removal of groups, such as phosphorylation or dephosphorylation. Example : Phosphorylation of isocitrate dehydrogenase (IDH) enzyme by protein kinase A (PKA), activating IDH to catalyze the citric acid cycle.

32. Transcriptional regulation : Gene expression is controlled by binding of transcription factors to specific DNA sequences, regulating mRNA synthesis. Example : Lac repressor protein binding to the lac operator DNA sequence, preventing transcription of the lac operon genes for lactose metabolism in E. Coli. Feedback inhibition : Metabolic end products bind to enzymes, inhibiting earlier steps in the pathway, preventing excessive flux and regulating metabolism. Example : ATP binding to phosphofructokinase-1 (PFK-1) enzyme, inhibiting its activity and reducing glycolytic flux when ATP levels are high.

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