ch369_f09_regul_notes

ch369_f09_regul_notes - Nitrogen metabolism (continued) -...

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Nitrogen metabolism (continued) - Chapter 15
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Fate of the carbon skeleton of a.a.’s that are broken down: In the “ glucogenic amino acids ”, the carbon is coverted to pyruvate or oxaloacetate. In “ ketogenic amino acids ”, the carbon is eventually converted to acyl CoA. Amino acids can be glucogenic, ketogenic, or both. When you have excess protein in your diet, the amine nitrogen of the amino acids are discarded (in urea cycle), and the carbons of the amino acids salvaged. Amino Acid Catabolism
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Catabolic Types of Amino Acids Glucogenic Alanine Arginine Aspartate Asparagine Cysteine Glutamate Glycine Histidine Methionine Proline Serine Valine Ketogenic Leucine Lysine Both Isoleucine Phenylalanine Threonine Tryptophan Tyrosine From Table 15-2
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Unnumbered, page 483 Amino acid catabolism. Example of Glucogenic Amino Acids (1)
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Unnumbered, page 484 (1) Amino acid catabolism. Examples of Glucogenic Amino Acids (2) - deamination of serine. What is done with the ammonia?
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Figure 15.11 The initial steps of valine degradation. Succinyl-CoA Valine catabolism (TCA cycle)
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Catabolism of phenylalanine. With PKU, diet must be monitored to keep Phe consumption low, and definitely no aspartame: aspartam e
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We get much of our nitrogen from the amino acids in proteins in our diet. How do we dispose of excess nitrogen?
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Nitrogen Disposal - through the “urea cycle”, with these end products: Mammals - excrete urea Birds and Reptiles - excrete uric acid Fish - excrete ammonia
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Figure 15.14 The urea cycle and related reactions. urea cycle *start here * The end of the Arg side chain looks just like urea. cycle again “pass the amine”
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Figure 15.12 The carbamoyl phosphate synthetase reaction. The carbamoyl phosphate synthetase reaction traps free ammonia as carbamoyl phosphate, which enters urea cycle.
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Figure 15.13 The four reactions of the urea cycle. urea cycle (4 reactions)
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The end of the Arg side chain looks just like urea. cytosol cytosol mito. matrix mito. matrix cytosol (mitochondria have transporters for citrulline & ornithine) mito. matrix urea cycle Regulation by allosteric activation of carbamoyl phosphate synthestase. TCA cycle mito. matrix cytosol cytosol
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Unnumbered, page 492 (1) Uric acid. Uric acid: Excreted by birds and some reptiles (uric acid packs more nitrogen with less associated water than urea). So birds don’t have to carry so much water in bodies. Product of purine catabolism in mammals.
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Unnumbered, page 492 (2) Xanthine oxidase. Excess uric acid in humans causes gout Purine bases (peroxisome) Gout - Too much purine to dispose of, uric acid crystallizes in joints. degradation
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3 extra slides
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Gets rid of excess lactate from muscles. Example of a process that must be coordinated
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This note was uploaded on 01/21/2010 for the course CH 369 taught by Professor Kbrowning during the Fall '07 term at University of Texas.

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ch369_f09_regul_notes - Nitrogen metabolism (continued) -...

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