Microbio February 17, 2010 Biosynthesis Cells break things down because they need to break things.. Another word for biosynthesis is ANABOLISM Anabolism Defined as : synthesis of complex molecules and cellular structures One part of anabolism is a turnover Continual degradation and resynthesis of cellular constituents Rate of biosynthesis approximately balanced by rate of catabolism (you are not going to make things faster than you can degrade things) one reason for this is ATP NADPH all of these comes from catabolism.. you cant do biosynthesis without catabolism.. you need that energy so u can expand it Requires a lot of energy In an bacterial cell there is one molecule of dna which requires 60,000 ATP?s General Properties of Biosynthesis Complex macromolecules are constructed from simpler precursors (think legos and making building) Requires energy input- hydrolysis of ATP Electron donor generally used- NADPH (for biosynthesis this is usually the donor) You can start with a few common precursors and generate diverse range of end products. Use of COMPARTMENTS in eukaryotes to separate anabolic and catabolic pathways. (In anabolism you want to make glucose and in catabolism you want to use glucose. REMEMBER GENERALIZATION : NADH ?MADE DURING CATABOLISM NADPH- USED DURING ANABOLISM General Definition: Amphibolic pathways: many enzymes used for both catabolism and anabolism. Some steps in amphibolic pathways use two enzymes- one for catabolism, one for anabolism. Permits independent regulation of catabolism and anabolism. Fixation of CO2 Basis for accumulation of carbohydrates on earth Occurs during dark or light-independent reactions of photosynthesis. Light reactions take place on membranes (thylakoids) Photosynthesis involves an transport chain? Dark reactions take place in soluble compartments (e.g chloroplast stroma of euk.) Performed by AUTOTROPHS( organisms that can get carbon from CO2) Main pathways to fix Co2 is the CALVIN CYCLE (also called Reductive pentose phosphate pathway) Calvin Cycle 3 stages Carboxylation Reduction Regeneration Carboxylation Riblose 1,50 Bisphosphate (RuBP) - 2x PGA 5c Sugar 3C Sugar Reduction Use of ATP and NADPH from light reactions PGA is converted to Glyceraldehyde 3- Phosphate Reversal of a Glycolytic reaction Regeneration Regenerates RuBP Produces Carbohydrates Will recognize this as Similar to Pentose Phosphate Pathway Summary of Calvin Cycle Incorporation of 1 CO2 uses ATP, 2 NADPH 6 turns of Calvin Cycle to produce 1 6C Sugar 6 CO2?s are needed to make 1 Glucose (6C sugar) 18 ATP and 12 NADPH are Consumed Other ways to fix CO2 Anaplerotic Reactions: (MEMORIZE THIS) Used by all organisms to fix small amounts of CO2 Occurs via some reactions in TCA Cycle that are reversed Reverse TCA cycle Whole cycle can run reverse in some anaerobes and archea Incorporates 4 Carbons per turn Uses 4-5 ATP per turn ( more than made in ?Catabolic? direction) Use of Carbon skeletons in Biosynthesis Carbon skeletons are used as starting substrates for Biosynthetic pathways. Examples are intermediates of the central metabolic pathways. Intermediates of calvin cycles. Fatty Acid Biosynthesis Fatty acids are biosynthesized two carbons at a time using an acyl carrier protein (ACP) ACP holds the growing fatty acid as its being synthesized. 2 carbon units from acetyl- CoA added repeatedly Fatty Acids uses: Fatty acids + Glycerol phospholipid Enzyme cofactors Added to some membrane proteins.
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