If you ate a clown, would it taste funny? Oh, wait, that s cannibalism . Anabolism

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1 If you ate a clown, would it taste funny? Oh, wait, that s cannibalism. Anabolism is about putting things together. Anabolism: The Use of Energy in Biosynthesis Anabolism energy from catabolism is used for biosynthetic pathways using a carbon source and inorganic molecules, organisms synthesize new organelles and cells antibiotics inhibit anabolic pathways a great deal of energy is needed for anabolism turnover continual degradation and resynthesis of cellular constituents by nongrowing cells metabolism is carefully regulated for rate of turnover to be balanced by rate of biosynthesis in response to organism s environment Table 11.1 Principles Governing Biosynthesis macromolecules are synthesized from limited number of simple structural units (monomers) saves genetic storage capacity, biosynthetic raw material, and energy many enzymes used for both catabolic and anabolic processes saves materials and energy More Principles to synthesize molecules efficiently, anabolic pathways must operate irreversibly in the direction of biosynthesis done by coupling breakdown of ATP to certain reactions in biosynthetic pathways drives the biosynthetic reaction to completion anabolic and catabolic reactions are physically separated located in separate compartments allows pathways to operate simultaneously but independently catabolic and anabolic pathways use different cofactors catabolism produces NADH NADPH used as electron donor for anabolism large assemblies (e.g., ribosomes) form spontaneously from macromolecules by selfassembly Precursor Metabolites generation of precursor metabolites is critical step in anabolism carbon skeletons are used as starting substrates for biosynthetic pathways examples are intermediates of the central metabolic pathways

2 most are used for the biosynthesis of amino acids The Fixation of CO 2 by Autotrophs the Calvin cycle the reductive TCA cycle the hydroxypropionate cycle the acetyl-coa pathway the 3-hydroxypropionate/4-hydroxybutyrate pathway Calvin Cycle used by most autotrophs to fix CO 2 also called the reductive pentose phosphate cycle in eukaryotes, occurs in stroma of chloroplasts in cyanobacteria, some nitrifying bacteria, and thiobacilli, may occur in carboxysomes inclusion bodies that may be the site of CO 2 fixation consists of 3 phases the carboxylation phase the reduction phase the regeneration phase three ATPs and two NADPHs are used during the incorporation of one CO 2 The Carboxylation Phase catalyzed by the enzyme ribulose 1.5-bisphosphate carboxylase (ribulose bisphosphate carboxylase/oxygenase) (RuBisCo) rubisco catalyzes addition of CO 2 to ribulose-1,5-bisphosphate (RuBP), forming 2 molecules of 3-phosphoglycerate The Reduction and Regeneration Phases 3-phosphoglycerate reduced to glyceraldehyde 3-phosphate RuBP regenerated carbohydrates (e.g., fructose and glucose) are produced Other CO 2 -Fixation Pathways the reductive TCA cycle used by some chemolithoautotrophs runs in reverse direction of the oxidative TCA cycle Figure 11.6

3 Other CO 2 -Fixation Pathways the hydroxypropionate cycle used by some archaeal genera and the green nonsulfur bacteria (also anoxygenic phototrophs) Figure 11.7 Other CO 2 -Fixation Pathways the acetyl-coa pathway methanogens use portions of the acetyl-coa pathway for carbon fixation involves the activity of a number of unusual enzymes and coenzymes Figure 11.8 The 3-Hydroxypropionate/4-Hydroxybutyrate Pathway first described in 2007 in an archeon uses 3-hydroxypropionate cycle uses unique reaction to produce 3-hydroxybutryate Gluconeogenesis Monosaccharides Polysaccharides Peptidoglycan Figure 11.9 Synthesis of Sugars and Polysaccharides Gluconeogenesis synthesis of glucose and related sugars from nonglucose precursors glucose, fructose, and mannose are gluconeogenic intermediates or made directly from them galactose is synthesized with nucleoside diphosphate derivatives bacteria and algae synthesize glycogen and starch from adenosine diphosphate glucose functional reversal of glycolysis, but the two pathways are not identical 7 enzymes shared 4 enzymes are unique to gluconeogenesis Figure Synthesis of Monosaccharides several sugars are synthesized while attached to a nucleoside diphosphate such as

4 uridine diphosphate glucose (UDPG) Synthesis of Polysaccharides also involves nucleoside diphosphate sugars e.g., starch and glycogen synthesis ATP + glucose 1-P ADP-glucose + PP i (glucose) n + ADP-glucose (glucose) n+1 + ADP Peptidoglycan Synthesis complex process involves use of UDP derivatives also uses bactoprenol, a lipid carrier, to transport NAG-NAM-pentapeptide units across the cell membrane cross links are formed by transpeptidation Patterns of Cell Wall Formation autolysins carry out limited digestion of peptidoglycan activity allows new material to be added to wall and division to occur inhibition of peptidoglycan synthesis can weaken cell wall and lead to lysis many commonly used antibiotics inhibit cell wall formation The Synthesis of Amino Acids many precursor metabolites are used as starting substrates for synthesis of amino acids carbon skeleton is remodeled amino group and sometimes sulfur are added Synthesis of Amino Acids Nitrogen assimilation Sulfur assimilation Amino acid biosynthetic pathways Anaplerotic reactions and amino acid biosynthesis Nitrogen Assimilation major component of protein, nucleic acids, coenzymes, and other cell constituents nitrogen addition to carbon skeleton is an important step potential sources of nitrogen: ammonia, nitrate, or nitrogen most cells use ammonia or nitrate ammonia nitrogen easily incorporated into organic material because it is more reduced than other forms of inorganic nitrogen

5 Sulfur Assimilation sulfur needed for synthesis of amino acids cysteine and methionine synthesis of several coenzymes sulfur obtained from external sources intracellular amino acid reserves Amino Acid Biosynthesis Branching Pathways used in the synthesis of multiple amino acids a single precursor metabolite can give rise to several amino acids biosynthetic pathways for aromatic amino acids also share intermediates Anaplerotic Reactions TCA cycle intermediates are used in many amino acid biosynthetic pathways replenishment of these intermediates is provided by anaplerotic reactions allow TCA cycle to function during periods of active biosynthesis e.g., anaplerotic CO 2 fixation e.g., glyoxylate cycle Anaplerotic CO 2 Fixation phosphoenolpyruvate (PEP) carboxylase phosphoenolpyruvate + CO 2 oxaloacetate + P i pyruvate carboxylase pyruvate + CO 2 + ATP + H 2 O oxaloacetate + ADP + P i reaction requires the cofactor biotin Glyoxalate Cycle other anaplerotic reactions are part of the glyoxalate cycle, a modified TCA cycle Figure The Synthesis of Purines, Pyrimidines, and Nucleotides most microbes can synthesize their own purines and pyrimidines purines cyclic nitrogenous bases consisting of 2 joined rings adenine and guanine pyrimidines cyclic nitrogenous bases consisting of single ring uracil, cytosine, and thymine nucleoside = nitrogenase base-pentose sugar nucleotide = nucleoside-phosphate

6 Phosphorus Assimilation phosphorus found in nucleic acids as well as proteins, phospholipids, ATP, and some coenzymes most common phosphorus sources are inorganic phosphate and organic phosphate esters inorganic phosphate (P i ) incorporated through the formation of ATP by photophosphorylation oxidative phosphorylation substrate-level phosphorylation organic phosphate esters present in environment in dissolved or particulate form hydrolyzed by phosphatases, releasing P i Purine Biosynthesis complex pathway in which several different molecules contribute parts to the final purine skeleton initial products are ribonucleotides deoxyribonucleotides formed by reduction of nucleoside diphosphates or nucleoside triphosphates Pyrimidine Biosynthesis begins with aspartic acid and high energy carbamoyl phosphate ribonucleotides are initial products deoxy forms of U and C nucleotides formed by reduction of ribose to deoxyribose Lipid Synthesis lipids major required component in cell membranes most bacterial and eukaryal lipids contain fatty acids fatty acids synthesized then added to other molecules to form other lipids such as triacylglycerols and phospholipids