34 AAs - Protein Turnover-1

34 AAs - Protein Turnover-1 - Amino Acids and Proteins:...

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Amino Acids and Proteins: Protein Turnover HNFE 3025 Fall 2009
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Proteins Represent about 14 – 16% of the body weight of healthy adults No storage form of protein or constituent amino acids – all proteins have a function: catalysis (enzymes) transport architecture (skeleton) movement (contractile proteins) protection (antibodies, T cell receptors, scavengers) signaling 2
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Overview of Protein Metabolism 3 Dietary Protein Amino Acids digestion absorption Intracellular Amino acids Proteins S D Specialized products deamination C skeletons Urea Intracellular Amino acids Protein S D Muscle and other tissues GI tract Liver Blood & extra- cellular fluid Urine Source of amino acids to make proteins: EXOGENOUS (dietary protein) and ENDOGENOUS (AAs released when cell protein is broken down)
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Protein Balance The amount of protein in a healthy adult remains fairly constant. Protein balance is the difference between synthesis and degradation (breakdown). During growth, training, and recovery PRO synthesis > PRO degradation During aging, sickness, starvation, and overtraining PRO synthesis < PRO degradation Protein balance = protein synthesis – protein degradation 4 Total Body Protein Protein Degradatio n Protein Synthesi s
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A Person In Protein Balance The total amount of protein (amino acids) taken in through the diet is equal to the loss of amino acids Losses Non-absorbed amino acids Normal degradation and catabolism of amino acids leading to loss as CO 2 and urea Other obligatory losses through sloughed off skin, hair loss and sweat 5 Protein Amino Acids D S S = D
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A Person Out of Protein Balance Positive Protein (N) Balance Increase in body protein Increased synthesis (S) Decreased degradation (D) Some combination of both Negative Protein (N) balance Decrease in body protein Decreased synthesis (S) Increased degradation (D) Some combination of both 6 Protein Amino Acids D S Protein Amino Acids D S S > D S < D ↑↑ S & D S & no D D & no S ↓↓ D & S S & D S & no D D & no S D & S
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25 50 75 100 125 150 10 0 10 20 30 40 50 N Balance or Efficiency of Dietary N retention Note that zero balance coincides with 100 mg N/kg/d (0.625 g PRO/kg/ d) 7
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Line representing N Equilibrium Median N intake for N equilibrium Relation between individual N balance corrected for dermal and misc losses and N intake for a large number of adults Nitrogen Balance vs. Intake 8
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Days to reach steady state for subject Days to reach steady state for subject
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This note was uploaded on 03/23/2010 for the course HNFE 3025 taught by Professor Mwhulver during the Spring '10 term at Virginia Tech.

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34 AAs - Protein Turnover-1 - Amino Acids and Proteins:...

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