Amphibolic nature of kreb's cycle

Amphibolic nature of kreb's cycle

• 2.
  Cells are constantlycarrying out thousands of chemical reactions needed to keep the cell, and your body as a whole, alive and healthy. These chemical reactions are often linked together in chains, or pathways. All of the chemical reactions that take place inside of a cell are collectively called the cell’s metabolism. Overview of metabolism
• 3.
  Metabolic pathways canbe broadly divided into two categories based on their effects. Photosynthesis, which builds sugars out of smaller molecules, is a "building up," or anabolic, pathway. In contrast, cellular respiration breaks sugar down into smaller molecules and is a "breaking down," or catabolic, pathway. ATP ATP + +
• 4.
  • Contains bothcatabolic and anabolic reactions. • Catabolic – Energy from oxidation of acetyl CoA is stored in reduced coenzymes. • Anabolic – Several intermediates are precursors in biosynthetic pathways Krebs Cycle is Amphibolic
• 5.
  The citric acidcycle (Krebs cycle, Tricarboxylic acid cycle) includes a series of oxidation-reduction reactions in mitochondria that result in the oxidation of an acetyl group to two molecules of carbon dioxide and reduce the coenzymes that are reoxidized through the electron transport chain, linked to the formation of ATP An overview of TCA cycle
• 6.
  Citrate Isocitrate α ketoglutarateSuccinyl CoA Succinate Fumarate malate Oxlaoacetate Acetyl CoA PyruvateCO2 Fattyacid Cholesterol Amino Porphyrin Isoleusine methionine valine Odd chain fatty acid Aspartate phenylalanine tyrosine Glucose Acids • anabolic pathways (red arrows) • anaplerotic reactions replenish depleted cycle intermediates (dark green arrows). • Catabolic – Energy from oxidation of acetyl CoA is stored in reduced coenzymes. • Anabolic – Several intermediates are precursors in biosynthetic pathways.
• 7.
   Anaplerosis isa series of enzymatic reactions in which metabolic intermediates enter the citric acid cycle from the cytosol.  Cataplerosis is the opposite, a process where intermediates leave the citric acid cycle and enter the cytosol. In muscle, anaplerosis is important for increasing citric acid throughput during periods of exercise. Anaplerosis and Cataplerosis
• 8.
  • The reactioncatalyzed by pyruvate carboxylase that replenishes oxaloacetate to the TCA cycle is a good example of an anaplerotic, or “filling up,” reaction. • pyruvate+ CO2 + ATP +H2O → oxaloacetate + ADP + Pi + 2 H+ • This reaction assures that there is sufficient oxaloacetate for condensation with acetyl CoA. In fact, acetyl CoA stimulates pyruvate carboxylase. • This reaction is most important, especially in liver and kidney.
• 9.
  There is someevidence that anaplerosis is required for a glucose-induced rise in mitochondrial ATP production. Some amino acids (the building blocks of proteins) enter and leave the citric acid cycle through anaplerosis and cataplerosis. Reactions Enzymes Tissue /organism Pyruvate +HCO3̄̄̄̄̄ + ATP Pyruvate carboxylase oxaloacetate + ADP+Pi Lever, kidney Phosphoenolpyruvate+CO2+GDP PEP carboxylase oxaloacetate+GTP Heart, skeletal muscles Phosphoenolpyruvate+HCO3 PEP carboxylase oxaloacetate+Pi Higher plant, yeast, bacteria Pyruvate +HCO3 + NADPH malic enzyme malate+NADPH+ Eukaryotes and prokaryotes Anaplerotic Reactions
• 11.
   Protein mayserve an excellent sources of nutrient energy  Catabolism of amino acids provides: succinate, oxaloacetate, fumarate, αketoglutarate.  Pyruvate (from glycolysis) • acetyl CoA stimulates pyruvate carboxylase Proteins can also be broken down to feed into the citric acid cycle and generate energy Under extreme starvation in animals or during senescence in plants polypeptides are cleaved to amino acids, amino group is cleaved off of amino acid forming an organic acid that can enter the citric acid cycle
• 12.
  Oxaloacetic acid Fumaric acid Succinic acid α ketoglutarate Pyruvic acid Acetyl CoA Alanine, cysteine, glycine,serine, threonine, tryptophan Tryptophan, leucine, isoleucine Arginine, Glutamine, Histidine, Proline Isoleucine, methionine, valine Phenylalanine, Tyrosine Asparagine, aspartate NH3 Urea NH3 Urea NH3 Urea NH3 Urea NH3 Urea NH3 Urea