Protein & Amino Acid Metabolism and The Urea Cycle
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| Can amino acids be stored | No
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| What are amino acids borwken down and used for | Fuel or as building blocks for glucose and lipid synthesis
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| The break down of amino acids generates what | Ammonia
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| What are the chemical formulas for ammonia and ammonium | NH3, NH4+
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| Which is membrane permeable ammonia or ammonium | Ammonia
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| At a pH less then the pK the equation is going to shift to the | Protonated form
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| Why is ammonia so toxic | It increases pH which alters redox balanc and can disrupt protien structure function and it inhibits ox phos by breaking down the H+ gradient
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| Where do whe get our amino acids | Dietary protein, endogenous proteins turnover, endogenous AA synthesis
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| What do we do with amino acids | Synthesis of other N containing molecules, degrade it into C which is used fo synthesis of glucose, fatty acids, ketones and N which is excreted in urea
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| Amino acids are important for the CNS because | Somone amino acids act as neurotransmitters and many neurotransmitters are synthesized from amino acids
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| What is nitrogen balance | Nitrogen input = nitrogen output
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| What is Positive nitrogen balance | N input > N output
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| Who would be seen in positive N balance | Children, Pregnant women
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| What is Negative nitrogen balance | N input < N output
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| Who would be seen in negative N balance | Those with a dietary deficiency or those with catabolic stress such as an infection
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| What are essential amino acids | Phenylalanine, Valine, Tyrptophan, Threonine, Isoleucine, Methionine, Histidine, Arginine, Lysine, Leucine
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| Alanine is synthesized from | Pyuvate
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| Aspartate is synthesized from | Oxaloacetate
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| Glutamate is syntehsized from | Alpha keto gluterate
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| What amino acid is essention only for growth and is generated int eh urea cycle | Arginine
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| The S in cysteine comes from where | Methionine
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| Tyrosine is made from | Phenylalanine
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| What are the three cofactors important for amino acid synthesis | Pyridoxal phosphate, Tetrahydrofolate, Tetrahydrobiopterin (BH4)
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| Pyridoxal phosphate is made from | Vitamin B6
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| A defect in a transporter for cystine and basic amino acids which can result in kidney stones | Cystinuria
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| A defect in the transporter for neutral amino acids and generaly asymptomatic | Hartnup disease
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| Amino acids cant be further catabolized until the | amino group has been removed
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| The nitrogen component of degraded amino acids is excreted as | Urea
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| Transamination is catalyzed by | Aminotransferases (transaminases)
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| How does transamination work | The amion acid gives its amino group to alpha-ketoglutarate producing glutamate. The original amino acid has been converted to its corresponding keto acid.
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| The enzyme that catalyzes the transamination of Aspartate to Oxaloacetate is | Aspartate aminotransferase (AST)
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| The enzyme that catalyzes the transamination of Alanine to Pyruvate is | Alanine aminotransferase (ALT)
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| Aminotransferases are intracellular proteins and are not usually found in the | Plasma
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| High serum levels of ALT and AST would indicate | A liver disease
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| What cofactor do aminotransferases require | Pyridoxal phosphate
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| What is pyridoxal phosphate synthesized from by the liver | Vitamin B6
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| Glutamate is deaminated by | Glutamate dehydrogenase (GDH)
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| What are the products of Glutamate deamination | Ammonia and alpha-ketoglutarate
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| Where does glutamate deamination primarily occur | Liver and kidneys
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| Free ammonia is produced by what other metabolic processes | Purine metabolism, bacterial metabolism in the gut, metabolism of serine and threonine
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| What can carry two ammonia molecules to the liver | Glutamine
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| Ammonia can be tranpsorted to the liver as what amino acid | Alanine
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| Amino acids are classfied into what two groups depending on what happens to the carbons | Glucogenic or ketogenic
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| Amino acids that are ultimately degraded to pyruvate or TCA cyle intermediates are classified as | Glucogenic
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| Amino acids that are ultimately degraded into acetyl CoA or acetoacetate are classified as | Ketogenic
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| What two amino acids are strictly ketogenic | Lysine and leucine
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| Aspartate, alanine, and glutamate are strictly | Glucogenic
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| Insulin promotes | Amino acid uptake and protein synthesis
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| Glucocorticoids induce | Ubiquitin synthesis
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| Glucagonand cortisol stimulate | Uptake of amino acids into the liver
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| The brain needs amino acids for synthesis of | Neurotransmitters
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| Muscle is a major source of amino acids in the | Fasted state
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| Teh liver uses a lto of amino acids in the | Fasted state
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| A state of increased fule usage in which the body needs energy and precurs to mount a defense against infection heal wounds, ect | Hypercatabolic state
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| A hypercatabolic state results in what type of nitrogen balance | Negative nitrogen balance
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| The disposal form of ammonia | Urea
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| Where does the urea cycle primarily occur | Liver
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| Where is urea excreted | Kidneys
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| Where do the two nitrogens of urea come from | Ammonia and aspartate
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| What is the precurso of both ammonia and aspartate | Glutamate
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| HCO3 + NH4 --> Carbamoyl phosphate | Carbamoyl phosphate synthase 1 (CPS1)
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| Carbamoyl Phosphate + Ornithine --> Pi + Citrulline | Ornithine transcarboylase (OTC)
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| Is the synthesis of urea reversible | No
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| The first two steps of the urea cycle take place in the | Mitochondria
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| The nitrogen in the first step comes from ... and this is catylzed by ... | Ammonia, CPS1
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| What is the rate limiting step of the urea cycle | CPS1
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| The second nitrogen in urea comes from | Aspartate
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| What links the TCA cycle to the urea cycle | Fumarate
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| Is arginine produced from the urea cyle | Yes
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| Is ATP used inteh urea cycle | Yes
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| What is regenerated and transported back inot the mitochondria where OTC uses it to make citrulline | Ornithine
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| Regulation of the urea cycle is primarily based on what | Substrate availability
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| Transcripton/translation of the urea cycle enzymes is induced by | High protein diet or prolonged fasting
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| What stimulates carbamoyl phosphate synthase 1 (CPS1) | N-acetylglutamate (NAG)
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| What is NAG synthesized from | Acetyl CoA and glutamate
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| Acetyl CoA + Glutamate --> NAG | NAG synthase
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| Can ura cross membranes and diffuse into the blood | Yes
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| Where is urea filtered and excreted | Kidneys, urine
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| Some urea diffuses inot the ... and is cleaved by ... | Intestines, bacteria
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| What is the measure of urea concentration in the blood | Blood Urea Nitrogen (BUN)
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| BUN levels reflect the function of the | Kidney and liver
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| BUN levels depend on | Diet
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| Urea cycle impairment results in | Hyperammonemia
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| What is hyperammonemia | Increased blood levels of ammonia
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| Tremors, agitation, slurring of speech, blurred vision, vomiting, hypotonia, seizures, mental retardation, cerebral edema and coma are symptoms of | Hyperammonemia
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| Kidney failure can lead to | hyperammonemia
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| All hereditary urea cycle disorders are ... except for ornithine transcarbamoylase deficiency | Autosomal recessive
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| Ornithine transcarbamoylase deficiency is | X-linked
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| What is the most common urea cycle disorder | Ornithine transcarbamoylase (OTC) deficiency
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