Metabolism
	Carbohydrate Metabolism - Fatty Acids and Lipid Metabolism - Amino Acid Metabolism - Nucleotide Metabolism - Energy Metabolism

Metabolism Carbohydrate Metabolism Glycolysis Pathway Glycolysis was one of the first metabolic pathways studied and is one of the best understood, in terms of the enzymes involved, their mechanisms of action, and the regulation of the pathway to meet the needs of the organism and the cell. The glycolytic pathway is extremely ancient in evolution, and is common to essentially all living organisms. Lactose Synthesis Oxidative reactions of the pentose phosphate pathway Starch Synthesis Sucrose Synthesis The Citric Acid Cycle The Krebs cycle, also called the citric acid cycle, is a fundamental metabolic pathway involving eight enzymes essential for energy production through aerobic respiration, and, like glycolysis, arose early in evolution. This pathway is also an important source of biosynthetic building blocks used in gluconeogenesis, amino acid biosynthesis, and fatty acid biosynthesis.  Fatty Acids and Lipid Metabolism Beta-Oxidation of Fatty Acids Fatty acids provide highly efficient energy storage, storing much more energy for their weight than carbohydrates like glucose. Fatty acids are stored as triglycerides in adipose tissue, in which each triglyceride molecule contains three fatty acids and one glycerol.  Formation of Ketone Bodies from acetyl-CoA The acetyl-CoA produced by mitochondrial beta-oxidation of fatty acids enters the Kreb's cycle to produce energy, but that is not the only fate of acetyl-CoA. In liver mitochondria, some acetyl-CoA is converted to acetoacetate, beta-hydroxybutyrate, and acetone, collectively called ketone bodies. Mitochondrial Carnitine Palmitoyltransferase (CPT) System The oxidation of fatty acids is an important source of energy for ATP production in mitochondria through the entry of acetyl-CoA into the Krebs cycle. Fatty acids are oxidized inside the mitochondrial matrix but the fatty acids to be oxidized come from the cytos Omega Oxidation While the main route of fatty acid metabolism is through beta-oxidation, some minor metabolic pathways such as omega oxidation also contribute to the metabolism of fatty acids and other molecules. Omega oxidation occurs in the endoplasmic reticulum rather than the mitochondria, the site of beta-oxidation. Oxidation of odd-numbered chain fatty acid, from Propionyl-CoA to Succinyl-CoA The beta-oxidation of fatty acids in mitochondria progressively shortens fatty acids two-carbons at a time as acetyl-CoA units are removed with each round of the cycle. Fatty acids that enter beta-oxidation with an even number of carbons are converted entirely to acetyl-CoA, with the last round producing two acetyl-CoA molecules from one four carbon fatty acid. Oxidation of Polyunsaturated Fatty Acid Unsaturated fatty acids are those that contain one or more double bonds in their alkyl-chain. Polyunsaturated fats with two double bonds usually have one between carbons 9 and 10 in the alkyl chain and another three carbons away (carbons 12-13). Amino Acid Metabolism Biosynthesis of Arginine in Bacteria Biosynthesis of Chorismate in Bacteria and Plants The biosynthesis of all three aromatic amino acids (tryptophan, tyrosine and phenylalanine) begins with the metabolic intermediate chorismate. The biosynthesis of chorismate occurs only in plants and bacterial, not in animals. The first step in the pathway involves phosphoenolpyruvate (PEP) from glycolysis and erythrose-4-phosphate from the pentose phosphate pathway. Biosynthesis of isoleucine Isoleucine is an essential amino acid, only synthesized in plants and bacteria, and required in the diet by animals. In proteins, the hydrophobic isoleucine side-chain tends to reside with other hydrophobic residues in the interior of globular proteins or in transmembrane domains. Isoleucine biosynthesis begins with the common metabolic intermediate pyruvate, the endpoint of glycolysis.   Biosynthesis of leucine The Krebs cycle, also called the citric acid cycle, is a fundamental metabolic pathway involving eight enzymes essential for energy production through aerobic respiration, and, like glycolysis, arose early in evolution. This pathway is also an important source of biosynthetic building blocks used in gluconeogenesis, amino acid biosynthesis, and fatty acid biosynthesis.  Biosynthesis of Lysine in Bacteria Biosynthesis of neurotransmitters Neurotransmitters are signaling molecules used by neurons to communicate across chemical synapses. The receptors for neurotransmitters include G-protein coupled receptors (GPCRs) and ligand-gated ion channels. Biosynthesis of phenylalanine and tyrosine in bacteria and plants Biosynthesis of Proline in Bacteria Among the twenty amino acids encoded by the genetic code, proline is unique in having a cyclic structure with its side chain connected to the amino group to create a secondary amine. As a consequence of its cyclic structure, proline constrains the structure of proteins where it occurs, disrupting alpha-helices. Biosynthesis of spermidine and spermine The polyamines spermidine and spermine are expressed in a variety of tissues and are involved in the regulation of apoptosis, cellular proliferation, and progression through the cell cycle. Depletion of polyamines appears to reduce cell growth, and increased polyamine expression is associated with the cancer development and progression, making polyamine biosynthesis a target for the control of cancer. Biosynthesis of threonine and methionine Biosynthesis of Tryptophan in Bacteria and Plants The aromatic amino acid tryptophan is an essential nutrient, meaning that humans and animals do not themselves have the biosynthetic machinery to synthesize tryptophan but rely on dietary intake from bacteria and plants that do produce it. Biosynthesis of valine Catabolic pathways for alanine, glycine, serine, cysteine, tryptophan, and threonine Amino acids in the diet have one of two fates - either they are incorporated into proteins or they are broken down for energy and metabolic intermediates. They are not stored and the body also does not excrete them intact. Catabolic Pathways for Arginine, Histidine, Glutamate, Glutamine and Proline   Catabolic Pathway for Asparagine and Asparate Catabolic Pathway for Methionine, Isoleucine, Threonine and Valine Serine in E. Coli Pathway   The reactions that feed amino groups into the urea cycle Excess amino acids in the body can be used as a source of energy, with their carbon skeleton converted to metabolic intermediates such as acetyl-CoA or intermediates in the Krebs cycle. Nucleotide Metabolism Coming Soon Energy Metabolism Electrons -Transfer Reaction in Mitochondria

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