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35 Cards in this Set
- Front
- Back
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What factors add N and take it out?
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Positive: increase body protein during growth, pregnancy, convalescence following illness
Negative: decrease in body protein starvation, malnutrition, burns, trauma, surgery |
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What is the measure of nitrogen balance?
What does this really tell? What affects this measure? How stable is it? |
BUN: blood urea nitrogen
Really a reflection of kidney function Elevated: dehydration, cardiac failure, high protein diet, kidney disease Depressed: liver disease, 2nd and 3rd trimester pregnancy Varies a lot so a ratio is used instead with creatinine |
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Transamination
What does this? What else is formed? What is often utilized in this rxn? |
aminotransferase
aa loses amino group and has carbonyl instead (alpha-ketoacid). Usually gets amino group sent with alpha-ketoglutarate (abundant in cells) making it glutamate PLP (vitamin B6) |
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What types of people tend to get B6 deficiencies?
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Alcoholics, elderly, liver disease people, certain drugs
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How does B6 help aminotransferases?
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amino acid gives amino group to B6 so it goes from pyridoxal phosphate PLP to pyridoxamine phosphate PMP. PMP hands off amino group to alpha-ketoglutarate
two successive transaminations happen |
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What are two aminotransferases?
Location Rxn |
Alanine aminotransferase ALT: liver enzyme: catalyzes alpha-ketoglutarate to Glu and also itself becomes pyruvate (end point of glycolysis-> Glucose or ATP)
Aspartate aminotransferase AST: ubiquitous: a-ketoglutarate to glutamate, aspartate to oxaloacetate (intermediate in citric acid cycle, -> Glc or ATP) |
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What can alpha-ketoglutarate be converted to?
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ATP (it's an intermediate in citric acid cycle)
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Liver Enzyme Test looks at?
What do results indicate? What limitations does this test have? |
AST and ALT
AST/ALT = 1 normally Inflammation or injury of liver cause cells to release their ALT making the ratio <1 >1 is listed as ALT being underproduced: cirrhosis and alcohol abuse as this damages ALT expression It's a snapshot of current standings and doesn't show history |
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Where does gluconeogenesis primarily occur?
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Liver
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How does ammonia kill neurons?
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Astrocytes can't handle it. Glu levels go up, water floods in, cells end up lysing and dicing.
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What is the exception of ammonia serum levels 10-50 microM?
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Hepatic portal vein are above normal.
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What concentration of ammonia will put you in a coma?
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200microM
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What are the two ammonia carriers?
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Ala and Gln
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Why can't you send Glu out into the bloodstream?
What do you change it to? |
It's a neurotransmitter.
Gln or Ala |
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Where is the free amino acid pool?
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Plasma levels are actually quite low, even Gln and Ala.
Liver and muscle house most of them. |
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Outline the process of Alanine being an ammonia carrier to the liver.
Highlight key intermediates and their relevance. |
Amino acids transfer amino group to Glu
Glu transfers (turning back into alphaketoglutarate) to pyruvate making Ala via alanine transaminase ALT Ala then goes to the liver In liver Hepatic alanine transaminase (ALT^H) converts Ala back to pyruvate such that it can enter gluconeogenesis or citric acid cycle |
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What is a side effect of the alanine cycle?
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Glutamate levels shift to the liver
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Outline the process of glutamine as an ammonia carrier to liver. Include enzymes and substrates.
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Amino acids transfer amino group to make Glu
Glu condenses with ammonia NH4+ to make Gln via glutamine synthase Gln goes to the liver There enzyme glutaminase hydrolyzes Gln back to Glu and ammonia NH4+ |
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In the liver, what fates might Glu have?
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Can be turned into glucose and sent out
Can undergo oxidative deamination making alpha-ketoglutarate and ammonia and NADPH Can have transamination by AST to make alpha-ketoglutarate and aspartate |
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glutamine synthase
What does it catalyze? Predominantly found where? Does it require energy? How does the rxn go? What is a similar rxn we saw? |
Glutamate + ammonia to Gln
brain, kidneys, muscle, liver (perivenous cells at exit to keep ammonia from exiting) Yes. ATP is used to activate Glu (puts on phosphate group) that ammonia attacks (same as C-terminal Gly in ubiquitin by ubiquitin-activating enzyme) |
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glutaminase
Where is it found? What does it catalyze? |
In liver at entrance in periportal cells
Gln + H20 to Glu and ammonia |
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What enzyme catalyzes the oxidative deamination of Glu to ammonia and aKG?
What is it doing? How is it regulated? |
glutamate dehydrogenase GDH
Oxidizes as it deaminates making aKG, ammonia, AND NADH Allosterically activated by GDP and ADP, inhibited GTP and ATP |
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How many ATP's can be made from an NADH?
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2.5
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What is the chemical equation of Gln formation in muscles?
What is the true net? What is the implication? |
2Glu + NAD+ + ATP ---> Gln + aKG + NADH + ADP
1.5 net ATP Glu and Gln in muscle are energy storage molecules |
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What is the major way we lose nitrogen?
How much does it cost to get rid of one of these? |
Urea through urine
4 ATP equivalents to synthesize a urea |
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Where is urea formed?
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In periportal cells of liver and in the kidneys
Some parts take place in cytosol and some in mitochondrial matrix |
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What is the first big enzyme in trapping ammonia and consuming two ________ bonds?
Energy dependent? What is the rxn taking place? Where does it take place? |
Carbamoyl phosphate synthetase I (CPS1)... consumes two phosphoanhydride bonds
Uses 2 ATP bicarbonate activated (ATP) which goes with ammonia, then ATP to make carbamoyl phosphate liver mitochondria (20% of protein in the matrix) |
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Where is carbamoyl phosphate synthetase II?
What's its ammonia source? |
in cytosol
Gln |
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After carbamoyl phosphate is made, what happens to it generally?
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Condensation with ornithine to make citrulline
Citrulline intercepts Asp to make arginosuccinate Cleavage of arginosuccinate makes fumarate and Arg Hydrolysis of Arg makes urea and ornithine |
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Characteristic of citrulline
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neutral
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How do we know Arg isn't an essential amino acid?
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Made in the urea cycle
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Where does ATP get used in urea cycle?
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making carbamoyl phosphate (2)
making arginosuccinate (2) |
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Draw urea cycle.
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picture saved.
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Where do the two N come from that are in urea?
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The ammonia in the beginning and the aspartate that joins citrulline.
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What happens with the fumarate in the liver? What else is addressed?
Where is it effectively coming from? |
fumerase changes it to malate to put it into the mitochondria.
Malate to oxaloacetate (which with Glu makes aKG and Asp) This is using the Glu. Glu and aKG can swap back and forth in cytosol and mitochondria. Aspartate going in urea cycle comes out as fumarate |
