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Biochem Exam 6
Protein & Amino Acid Metabolism and The Urea Cycle
| Question | Answer |
|---|---|
| Can amino acids be stored | No |
| What are amino acids borwken down and used for | Fuel or as building blocks for glucose and lipid synthesis |
| The break down of amino acids generates what | Ammonia |
| What are the chemical formulas for ammonia and ammonium | NH3, NH4+ |
| Which is membrane permeable ammonia or ammonium | Ammonia |
| At a pH less then the pK the equation is going to shift to the | Protonated form |
| 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 |
| Where do whe get our amino acids | Dietary protein, endogenous proteins turnover, endogenous AA synthesis |
| 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 |
| Amino acids are important for the CNS because | Somone amino acids act as neurotransmitters and many neurotransmitters are synthesized from amino acids |
| What is nitrogen balance | Nitrogen input = nitrogen output |
| What is Positive nitrogen balance | N input > N output |
| Who would be seen in positive N balance | Children, Pregnant women |
| What is Negative nitrogen balance | N input < N output |
| Who would be seen in negative N balance | Those with a dietary deficiency or those with catabolic stress such as an infection |
| What are essential amino acids | Phenylalanine, Valine, Tyrptophan, Threonine, Isoleucine, Methionine, Histidine, Arginine, Lysine, Leucine |
| Alanine is synthesized from | Pyuvate |
| Aspartate is synthesized from | Oxaloacetate |
| Glutamate is syntehsized from | Alpha keto gluterate |
| What amino acid is essention only for growth and is generated int eh urea cycle | Arginine |
| The S in cysteine comes from where | Methionine |
| Tyrosine is made from | Phenylalanine |
| What are the three cofactors important for amino acid synthesis | Pyridoxal phosphate, Tetrahydrofolate, Tetrahydrobiopterin (BH4) |
| Pyridoxal phosphate is made from | Vitamin B6 |
| A defect in a transporter for cystine and basic amino acids which can result in kidney stones | Cystinuria |
| A defect in the transporter for neutral amino acids and generaly asymptomatic | Hartnup disease |
| Amino acids cant be further catabolized until the | amino group has been removed |
| The nitrogen component of degraded amino acids is excreted as | Urea |
| Transamination is catalyzed by | Aminotransferases (transaminases) |
| 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. |
| The enzyme that catalyzes the transamination of Aspartate to Oxaloacetate is | Aspartate aminotransferase (AST) |
| The enzyme that catalyzes the transamination of Alanine to Pyruvate is | Alanine aminotransferase (ALT) |
| Aminotransferases are intracellular proteins and are not usually found in the | Plasma |
| High serum levels of ALT and AST would indicate | A liver disease |
| What cofactor do aminotransferases require | Pyridoxal phosphate |
| What is pyridoxal phosphate synthesized from by the liver | Vitamin B6 |
| Glutamate is deaminated by | Glutamate dehydrogenase (GDH) |
| What are the products of Glutamate deamination | Ammonia and alpha-ketoglutarate |
| Where does glutamate deamination primarily occur | Liver and kidneys |
| Free ammonia is produced by what other metabolic processes | Purine metabolism, bacterial metabolism in the gut, metabolism of serine and threonine |
| What can carry two ammonia molecules to the liver | Glutamine |
| Ammonia can be tranpsorted to the liver as what amino acid | Alanine |
| Amino acids are classfied into what two groups depending on what happens to the carbons | Glucogenic or ketogenic |
| Amino acids that are ultimately degraded to pyruvate or TCA cyle intermediates are classified as | Glucogenic |
| Amino acids that are ultimately degraded into acetyl CoA or acetoacetate are classified as | Ketogenic |
| What two amino acids are strictly ketogenic | Lysine and leucine |
| Aspartate, alanine, and glutamate are strictly | Glucogenic |
| Insulin promotes | Amino acid uptake and protein synthesis |
| Glucocorticoids induce | Ubiquitin synthesis |
| Glucagonand cortisol stimulate | Uptake of amino acids into the liver |
| The brain needs amino acids for synthesis of | Neurotransmitters |
| Muscle is a major source of amino acids in the | Fasted state |
| Teh liver uses a lto of amino acids in the | Fasted state |
| 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 |
| A hypercatabolic state results in what type of nitrogen balance | Negative nitrogen balance |
| The disposal form of ammonia | Urea |
| Where does the urea cycle primarily occur | Liver |
| Where is urea excreted | Kidneys |
| Where do the two nitrogens of urea come from | Ammonia and aspartate |
| What is the precurso of both ammonia and aspartate | Glutamate |
| HCO3 + NH4 --> Carbamoyl phosphate | Carbamoyl phosphate synthase 1 (CPS1) |
| Carbamoyl Phosphate + Ornithine --> Pi + Citrulline | Ornithine transcarboylase (OTC) |
| Is the synthesis of urea reversible | No |
| The first two steps of the urea cycle take place in the | Mitochondria |
| The nitrogen in the first step comes from ... and this is catylzed by ... | Ammonia, CPS1 |
| What is the rate limiting step of the urea cycle | CPS1 |
| The second nitrogen in urea comes from | Aspartate |
| What links the TCA cycle to the urea cycle | Fumarate |
| Is arginine produced from the urea cyle | Yes |
| Is ATP used inteh urea cycle | Yes |
| What is regenerated and transported back inot the mitochondria where OTC uses it to make citrulline | Ornithine |
| Regulation of the urea cycle is primarily based on what | Substrate availability |
| Transcripton/translation of the urea cycle enzymes is induced by | High protein diet or prolonged fasting |
| What stimulates carbamoyl phosphate synthase 1 (CPS1) | N-acetylglutamate (NAG) |
| What is NAG synthesized from | Acetyl CoA and glutamate |
| Acetyl CoA + Glutamate --> NAG | NAG synthase |
| Can ura cross membranes and diffuse into the blood | Yes |
| Where is urea filtered and excreted | Kidneys, urine |
| Some urea diffuses inot the ... and is cleaved by ... | Intestines, bacteria |
| What is the measure of urea concentration in the blood | Blood Urea Nitrogen (BUN) |
| BUN levels reflect the function of the | Kidney and liver |
| BUN levels depend on | Diet |
| Urea cycle impairment results in | Hyperammonemia |
| What is hyperammonemia | Increased blood levels of ammonia |
| Tremors, agitation, slurring of speech, blurred vision, vomiting, hypotonia, seizures, mental retardation, cerebral edema and coma are symptoms of | Hyperammonemia |
| Kidney failure can lead to | hyperammonemia |
| All hereditary urea cycle disorders are ... except for ornithine transcarbamoylase deficiency | Autosomal recessive |
| Ornithine transcarbamoylase deficiency is | X-linked |
| What is the most common urea cycle disorder | Ornithine transcarbamoylase (OTC) deficiency |
Created by:
mhaynes
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