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68 Cards in this Set
- Front
- Back
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Zero Nitrogen Balance
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Nitrogen intake=excretion
In mature healthy person anabolism=catabolism and N balance =0 |
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Positive Nitrogen Blaance
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Nitrogen intake is greater than Nitrogen excretion
This occurs in growing animal, pregnancy, and recovery from starvation |
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Negative Nitrogen Balance
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Catabolism is greater than anabolism
this occurs in starving animal, acute injury, senescence, and aa defiency |
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Essential amino acids
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histidine
isoleucine leucine lysine methionine phenylanine threonine tryptophan valine |
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Why is methionine an essential aa if we have the enzymes to make it?
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bc we cant make it at an effient rate
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describe protein degradation in the stomach
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when pH is less that 5.0
pepsinogen --> pepsin pepsin hydrolyzes proteins to peptides at points involving aromatic amino acids, leucine, and acidic amino acids |
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Descibe protein degradation in the intestine
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trypsinogen uses enteropeptidase to become trypsin. trypsin then activates more trypsinogen to bcom trypsin, chymotrypsinogen to become chymotrypsin, procarboxypeptidases to become carboxypeptidases, and proelastase to become elastase.
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Where are the inactive zymogens secreted from?
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the pancrease, they dont become active until they get to SI
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What happens once trypsin is activated?
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All other zymogens become activated
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what makes enteropedptidase that causes activation of trypsinogen?
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make by intestinal cells so zymogens cannot be active until in SI
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where does trypsin cleave?
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after Arg or Lys
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Where does chymotrypsin cleave?
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after tyr, phe, or trp.
Basically after aromatic rings |
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Where does elastase cleave?
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very small aa. Gly, Ala
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Where does carboxypeptidase B cleave?
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Must be the last aa of the chain and must be Arg or Lys. So it cleave right in front of the aa to cleave it off peptide
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endopeptidase
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cleaves w/i the polpeptide chain. Exampes trypsin, chymotrypsin, elastase
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exopeptidases
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only cleaves off last aa.
example is carboxypeptidase B |
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why are proteases on the intestinal lining?
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bc if not all are free aa and some are some peptides, aminopeptidase and carboxypeptidase cleave the pp to be absorbed
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most common disease of aa transport
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cystinuria. the gene that encodes for aa transport in the intestinal cells is mutated
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cystinuria
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defect in the reabsorbtion of dbasic aa(where COOH is protonated) so aa like cystine, ornithine, arginine, and lysine cant be reabsorbed in kidney and intestine. result is kidney stone from poorly soluble cystine.
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cystinuria treatment
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increase fluit intake and Oral intake of potassium citrate to increase urine pH to 7.5
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dibasic aa difiently absorbed in cystinuria
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lysine
arginine ornithine cystine |
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in the breakdown of aa what is the first task the cell must accomplish?
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remove the alpha amino group
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two major mechanisms of nitrogen removal from aa.
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1. transamination
2. oxidative deamination |
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transamination
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start out with an aa and alpha ketoglutarate. Use PLP and amino transferase to move Nitrogen of aa to alpha ketoglutarate. so end up with Glutamate and an alpha keto acid
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What is PLP?
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an intermediate carrier for the amino group. the important reactive group on PLP is the aldehyde bc that is where the amino group binds to be transferred.
The nitrogen group binds the aldehyde of PLP so it becomes PMP and PMP transfers the N group to alpha ketogluterate |
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How can the aa Ala make the Krebs intermediate pyruvate?
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by using alanine aminotransferase and PLP, Nitrogen of Ala is move to alpha ketogluterate. End up with Glutamate and pyruvate
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How can the aa aspartate bcome the krebs intermediate oxaloacetate?
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Using aspartate aminotransferase and PLP, aspartate gives its nitrogen group it alpha ketogluterate so end up with glutamate and oxaloacetate
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What is oxidative deamination?
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since all the aa N groups go to glutamate, this is way to get rid of glutamate. If ADP or GDP is hi activates glutamate dehydrogenase this causes glutamate to become alpha ketoglutarate + NH4.
NAD becomes NADH in this rxn |
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When is oxidative deamination inhibited?
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with high ATP or GTP because Krebs does not need to occur so dont need alpha ketoglutarate.
Oxidative deamination is activated by hi ADP or GDP |
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Problem with oxidative deamination
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build up of free NH4, which is very toxic so must go through urea cycle
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Why is NH4 Toxic?
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Bc NH4 + alpha ketogutarate
-> Gultamate + NH4 -> glutamine So with too much NH4, alpha ketoglutarate and glutamate decrease. so cant go through krebs to make ATP and cant make NT |
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Where is Urea Produced?
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In liver
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Urea Cycle
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1.CO2 + NH4 bcome carbonyl phosphate with enzyme carbomoyl phoshate synthtase
2. Ornithine becomes Citruline with enzyme ornitine transcarbomolase. at this point the P from carbomoy phosphate leaves 3. Cituline moves to cytosol and becomes argininocuccinate with argininosuccinate synthetase. Aspartate and ATP bcome AMP and PP. 4.Arginosuccinate uses argininosuccinase lyase to become argine and Fumarate is released 5. Argine uses arginase to become ornithine and urea is releases in cytosol |
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rate limiting step of urea cycle
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CO2 + NH4 uses carbamoyl phosphate synthetase to become carbamoyl phosphate.
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What regulate Urea Cycle?
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When arginine is hi it activates N acetylglutamate synthase to make N aceylglutamate. N acetylglutamate activates Carbomoyl Phospate Synthetase I.
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Where do the N atoms in urea orginate from?
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glutamate from oxidative deaminateion
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Treatment of hyperammonemia
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Low protien diet and/or alternate pathways fro nitrogen excretion.
Take sodium benzoate to conjugate with glycine to form hippurate to pee out Take phenylbuyrate which is converted to phenylacetate which becomes conjugated with glutamine to form phenylacetylglutamine to pee out |
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2 group of aa
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depends on products of catabolism
1. ketogenic aa 2. glucogenic aa |
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Ketogenic aa
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degraded to acetyl CoA or acetoacetyl CoA
they can produc ketone bodies |
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Glucogenic aa
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degraded to pyruvate, alpha ketoglutarate, succinyl CoA, fumarate, or oxaloacetate
their C skeleton can be used for gluconeogenisis |
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Ketogenic aa
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Leucine
Lysine |
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Glucogenic and Ketogenic aa
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Isoleucine
Phenylalanine Tryrosin Tryptophan Threonine |
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two genetic defects in aa catabolism
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1. PKU
2. Maple syrup urine disease |
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PKU
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defect in catabolism of phe
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Maple syrup urine disese
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defect in catabolism of ile, leu, and val (Branched chain aa)
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the one exception where transamination is not the first step of catabolism
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Phe
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normal catabolic steps of Phe
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1. hydroxylation to form tyrosine catalyzed by phenylaline hydroxlase
2. transamination of tyrosine 3. catabolism of the alpha keto acid of tyrosine (Fumerate and Acetyl Co A) |
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What is need to convert Phe to Tyr
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BH4 and pheylaline hydroxlase
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What regenerated BH2 to BH4 after phe is converted to tyr?
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dihydrobiopterin reductase w/ NADH as reducing agent
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PKU affected gene
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phyalalinine hydroxlase (99%)
Dihydorbiopterin reductase 1% |
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symptoms of PKU
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mental retardation, CNS damage, and hypopigmentation
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metabolic consequences of patients with PKU
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Phe can undergo transamination and make phenylpyruvate, phenylpyruvate then becomes phenyllactate and phenylacetate
Since Phe cant be converted to Tyr, Tyr is low so tyrosine becomes an essential aa. with lo tyrosine, decrease in protein, melanin, catecholamine, and fumerate |
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Normal catabolism of branched aa (isoleucine, leucine, and valine)
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1. transamination
2. alpha keto acid is decarboxylated to acyl Co A this rxn is catalyzed by branched chain alpha ketoacid dehydrogenase |
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Affected gene of MSUD
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genes that encode for branched chain alpha keto acid dehdrogenase complex (BCKAD) has 3 catalytic subunits and two regulatory subunits
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five molecules that are precursors to the nonessential aa
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1. a ketoglutarate family
(makes glutamate to glutamine) 2. oxaloacetate family (makes aspartate) 3. pyruvate family (makes alanine) 4. 3 phosphoglycerate family (makes serine, and serine plus met is cysteine) 5. Tyrosine Synthesis from phe |
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synthesis of glutamate
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1. reductive amination
a ketogluterate + NH4 -> glutamate catalyzed by glutamate dehydrogenase NADH ->NAD 2. by transamination. aa becomes a ketoacid and akg become glutamate |
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sythesis of glutamine from glutamate
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glutamate + NH4 -> glutamine
rxn catalyzed using glutamine synthetase and ATP |
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How to get to glutamate from glutamine
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use glutaminase
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How is alanine made?
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transamination
pyruvate + glutamate --> alanine + aKG rxn catalyzed by aminotransferase |
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how is aspartate made?
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oxaloacetate + glutamate -->
aspartate + aKG catalyzed by aminotransferase |
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important structural components of tetrahydrofolate (FH4)
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6 methylpterin
p aminobenzoate glutamate carries 1 C units |
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important structural componnets of S adenosylmethionine
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methioine
adenosine transfer group of CH4 so methylates stuff |
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Explain role oftetrahydrofolate is synthesis of glycine
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serine + FH4 -> glycine + N5,N10 methylene tetrahdrofolte
catalyzed by serine hdroxymethyl transferase the FH1 accepts one of serines carbon units |
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Methyl transfer cycle that utilizes S adenosylmethionine
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adoMet ->
s adenosylhomocysteine bc lost methyl group this is catalyzed by methyltransferases the S adenosylhomocysteine is hydrolzed to homocysteine and the adenosine is lost. The homocystein can then make methionine with methionine synthase. the methionine can cycle back and become AdoMet by adding ATP and methionine adenosyl transferase |
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NT synthesis from tyrosine
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Tyrosine used tyrosine hydroxlase and BH4 to become Dopa.
Dopa uses PLP and aromatic aa decarboxylase to become dopamine. dopamine uses dopamine hydroxlase to become norepi Norepi uses pheylethanolamine N methyltransferase and AdoMet to become epinephrine |
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Cofactor required fro amino transferase
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PLP
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NT syntheisis from tryptophan
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tryptophan uses tryptophan hydroxylase and BH4 to become S Hydroxytryptophan
S hydroxytryptophan uses aromatic aa decarboxylase and PLP to become serotonin |
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NT syntheisis from glutamate
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glutamate uses glutamate decarboylase and PLP to bcome GABA
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