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23 Cards in this Set
- Front
- Back
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How is ammonia made?
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Degrade a-amino acids
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Why can't ammonia be transported by the blood?
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Its highly toxic
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How do you produce E in the post absorptive states?
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Use the C skeletons (catabolism)
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How can the carbon skeletons of aa be used?
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carbon skeletons of aa are converted into intermediates that are used in the CAC:
-They can be metabolized into CO2 and H2O -They can be used in gluconeogenesis |
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Why are there so many paths to degrading aa?
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High variability of the side chains of aa
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What happens when the a-amino group is removed from an aa?
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-get an oxidized hydrocarbon
-they are amphibolic intermediates cuz they can be used in either an anabolic or catabolic way -all these intermediates can be fed into the CAC |
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What are the 7 amphibolic intermediates that can feed into the Krebs cycle?
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Pyruvate
Acetyl CoA Acetoacetate Oxaloacetate Fumarate Succinyl CoA a-Ketogluterate |
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Which aa feed into these intermediates?
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1) Pyruvate: Alanine, Cysteine, Glycine, Serine, Threonine, Tryptophan
2) Acetyl CoA: Isoleucine, Leucine, Threonine 3) Acetoacetate: Leucine, Lysine, Phenylalanine, Tryptophan, Tyrosine 4)OAA: Asparagine, Aspartate 5) Fumarate: Aspartate, Phenylalanine, Tyrosine 6)Succinyl CoA: Isoleucine, Methionine, Valine 7)a-Ketogluterate: Arginine, Glutamine, Glutamate, Histidine, Proline |
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What is a glucogenic aa?
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aa that will feed directly into the CAC or through pyruvate
-these aa will be converted to glucose during gluconeogenesis -amphibolic intermediates: a-KGA, Succinyl-CoA, Fumarate, OAA and pyruvate |
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What are ketogenic aa?
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Cannot be used for NET production of glucose, but can form ketone bodies
-Leucine, Lysine only -Amp. interm: Acetyl CoA and Acetoacetate |
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What are the 3 types of ketone bodies?
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-Acetone: result of spontaneous decarboxylation of acetoacetate
-Acetoacetate -B-hydroxybutiric acid -Acetoacetate and B-hydroxybutiric acid are interconvertible and can both be used to form acetyl CoA |
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Which aa are boh ketogenic and glucogenic?
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(3 T's, I & P)
-Threonine -Isoleucine -Tryptophan -Tyrosine -Phenylalanine |
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How many dif rxns are involved in the caabolism of methionine?
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10
-9 degradation rxns -1 regeneration rxn (rxn 4) |
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What is the branch point of methionine catabolism?
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-Homocysteine
-it can regenerate methionine or continue the degradation to succinyl CoA |
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Which biological functions is methionine important in?
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-Protein Synthesis (methioninw always the first aa cuz its a star codon)
-Precursor for Cystein -Precursor for SAM (methylating agent) |
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What is the active methyl cycle?
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Used to generate methyl groups (reactions 1-4 of methionine path)
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What is produced in rxn 1 of methionine path?
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SAM
-use enz: nethionine adenosyl transferase |
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What uses SAM?
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Sam used by methylases to methylate dif molec. This methylation changes the chemical/biological properties of the molec
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How is homocysteine formed?
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S-adenosylhomocystein is converted to homocysteine by enz: adenosylhomocysteinase
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What is the transsulfuration path?
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Rxns 3-10 of methionine rxn
-beginning of this path is the degradatiokn of homocysteine to cystathionine. This part of the path is also how cysteine is made |
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What happens if Vitamin B12 deficiency?
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-Methionine path struggles
-many associated problems including neurological disease |
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How can you have too much homocysteine?
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-Improper regeneration/degradation
- Mutations in conversion enz or folic acid deficiency (req'd for rxn 4) |
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Which diseases are ass't with hyperhomocysteinemia?
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Cardiovascular disease: homocysteine interferes w/ connective tissue, lesions in arteries which result in fromation of plaques obstructing arteries
Cognitive Impairment: problems judging/concentrating, homocystein levels affect nervous system Developmental Defects: -Neural tube defects: spina bifidam failure of neural tube to form or close -Anencephaly: failure of brain to develop Treatment: large doses of vit B6=> create a lot of PLP, which will sat enz and clear homocysteine. Can treat with folic acid to stimulate re-methylation to methionine. Folate reduces homocystein lvls, stabilize the MTHFR, enz req'd to methylate homocysteine back to methionine |
