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TAMU ANSC 303 - Protein Metabolism
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ANSC 303 1st Edition Lecture 20Outline of Last Lecture I. ProteolysisII. Rumen Protein UtilizationIII. Protein FractionsA. AB. B1, B2, B3C. CIV. Rumen Protein HydrolysisV. Microbial Crude Protein (MCP)VI. Using NPN to Make Microbial Protein VII. Limitations to Microbial Crude ProteinVIII. Excess Nitrogen IX. Nitrogen RecyclingOutline of Current Lecture I. Ruminant Protein Digestiona. Nitrogen Recyclingb. Protein Available for Ruminant Small Intestinec. Fate of Absorbed AAII. Protein Metabolisma. Use of AAb. AA in Liverc. Tissue Protein Turnoverd. Protein Synthesise. Protein/AA Catabolismi. Increases when:ii. Liver – main site1. Transamination2. deaminationCurrent LectureThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.I. Ruminant Protein DigestionA. Nitrogen Recyclinga. Excess NH3 is absorbed through the rumen wall to the bloodb. Quickly converted from urea in the liveri. Excess NH3 elevates blood pHii. Ammonia toxicity = increased NH3 levelsiii. UreaA. Excreted in urineB. Returned to rumen via salivaa. Rumination needs to be high b. No rumination = no urea recyclingc. Efficiency of nitrogen recycling decreases and nitrogen amount increasesB. Protein Available for Ruminant Small Intestinea. Microbial Proteini. Low quality protein in feed = good quality MCP A. Cheap feed doesn’t matterB. More econimic and beneficial to feed cheap feedii. High quality protein in feed = good quality MCP b. UIPi. Increases performanceii. NEEDS HIGHER QUALITY PROTEINc. Postruminal digestion and absorption is similar to that of monogastricsd. AA profile entering SI different from what is fede. Process:i. Di and tri peptides enter the small intestineii. Cross enterocyte A. Remember: enterocyte can take whatever it wantsB. Enterocyte can take any AA it wishesC. Glutamine - energy in enterocyteiii. Crosses baso-lateral membraneiv. AA now free v. AA enter liverA. Some AA leave for catabolism and protein synthesisvi. AA enter circulation to tissuesA. Some AA leave for catabolism and protein synthesisC. Fate of Absorbed AAa. Synthesis of tissue proteinsb. Synthesis of enzymes/hormones METABOLISMc. Transamination or Deaminationi. TransaminationA. Occurs with excess AAB. Synthesis of NON-ESSENTIAL AAii. DeaminationA. Occurs with dietary imbalanceB. This is when essential AA come into playC. If one AA is missing, synthesis stops and metabolism startsD. Break down of AAII. Protein MetabolismA. Use of Amino Acidsa. Each cell uses AA for its own needsb. Enterocyte gets first dibsc. Liver sees AA nextd. Tissues see AA lastB. AA in Livera. Primary site of AA uptakeb. Once AA entersi. 20% used for synthesis of proteinii. 57% catabolized in liverA. DeaminationB. Transaminationiii. 23% release into circulation A. High percent are branched chain AAB. Important to protein synthesisC. Tissue Protein Turnovera. Degradation and re-synthesis of protein b. Obligatory loss - some AA are needed for everyday lifec. Because some AA are degraded, they need to be replacedd. Synthesis should always be greater than degradationD. Protein Synthesisa. Ongoing activityb. Rates vary cell to cell c. VERY ENERGETICALLY EXPENSIVEi. Requires 5 ATP per peptide bondd. Accounts for about 20 % body energy E. Protein/AA Catabolisma. Increases when:i. Protein exceeds requirementsii. Composition of AA is unbalancediii. Gluoneogenesis is increasedb. Liver - main sitei. Remove amino group (NH3)ii. Transamination/deaminationA. Transaminationa. Transfer NH3 to a new AAb. Allows for reusual of nonessential AA (the body makes these)c. Requires B6 as coenzymed. Used to synthesize essential AAi. Not Lys or ThrB. Deaminationa. Transfer NH3 to urea and dispose of itb. Disposal c. The body has recycled as much as it could, so the rest is thrown


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TAMU ANSC 303 - Protein Metabolism

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