C485 Quiz 8

1) Regulation of the urea cycle is dependent on two amino acids. Explain the logic of this and explain how this dependence works.
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1) Regulation of the urea cycle is dependent on two amino acids. Explain the logic of this and explain how this dependence works.
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2) Transamination is different than incorporation of ammonia into a molecule. Explain how this is so.
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3) When ammonia is incorporated into a molecule biosynthetically, what are the two common sources for the ammonia? What are the usual products in each case? (One of these processes occurs in the urea cycle.)
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4) The urea cycle uses a third source of ammonia that is unique to the liver. What is this process?
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5) Which amino acids are: glucogenic, ketogenic, both
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5A)What are the two pathways for serine degradation? What cofactor plays an essential role in this process?
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5B) draw the mechanism of the reaction that liberates ammonia.
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5C) Draw the mechanism of the other reaction.
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6) One of the serine degradation pathways forms an amino acid. How is this amino acid degraded? List all the cofactors that are essential to this process. In some respects, this process resembles a TPP-catalyzed process that is very important in biology. What is that process and how does it resemble this one, even though a different cofactor is used.
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7) The degradation of threonine takes place by three different pathways. How are each of these pathways related to serine degradation? Classify the type of PLP reaction catalyzed in each of these threonine degradation pathways.
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8) What cofactor is responsible for binding formaldehyde (structure of chemically relevant portion)? What oxidation states does this carbon-carrying cofactor adopt? What is the one carbon equivalent (i.e. MeOH, formaldehyde, etc...)9) What is the end product of the solely ketogenic branched chain amino acid? Starting from the amino acid, what cofactors are required to obtain this molecule?10) In what way is the degradation of branched chain amino acids like fatty acid oxidation? Where does BCAA degradation take place? Which BCAA degradation is most similar to FAO? Explain.11) Draw the structure of S-adenosylmethionine. What is its biological function?12) Methionine is degraded to a four carbon molecule via the initial formation of cystathionine. Outline the steps in the formation of cystathionine from its immediate amino acid precursors.13) What is cystathionine converted to? What essential cofactor is used in this transformation? Classify the type of cofactor reaction used. (i.e. what is the reaction)14) The four carbon molecule derived from methionine is converted into a Krebs cycle intermediate. What is this molecule? What cofactors are involved in this transformation?15) The transfer of a methyl group from S-adenosylmethionine generates what product? Outline the conversion of this molecule to cystathionine.16) NAD+ is sometimes used as a true cofactor rather than a substrate. Such a transformation takes place in methionine metabolism. Explain the mechanism of this transformation.