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60 Cards in this Set
- Front
- Back
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What are the different fates of a.a. in cells?
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1. Protein via protein synthesis
2. Degredation into a. Nitrogen b. Carbon |
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In a typical fed adult, how does the synthesis of protein compare to the degredation?
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The rates are equal and there is no net degredation or production
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What is the typical protein in the US diet? High protein diet?
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100 g/day
High protein: 600 g/day |
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Where does the a.a. pool come from?
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1. Body protein (400 g/day)
2. Dietary protein 3. synthesis of non-essential a.a. |
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What are possible products of the a.a. pool?
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1. Synthesis of n-containing compounds, porphyrins, creatine, neurotransmitters (30 g/day)
2. Body protein (400 g/day) 3. Burned as fuel = CO2 4. Glucose, glycogen 5. Ketone bodies, FA, steroids |
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What is the protein selected for degredation tagged with?
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Ubiquitin
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Does tagging the proteins with ubiquitin require energy?
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Yes, it uses ATP and produces AMP
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Once tagged with ubiquitin, what happens to the protein?
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Degredation by a cytosolic proteasome
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What happens to the protein once inside the proteasome?
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Protein is unfolded, deubiquinated and degraded to peptide fragments
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Does the degredation that occurs within the proteasome require energy?
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Yes- it is ATP dependent
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What happens to the peptide fragments and ubiquitin released from the proteasome?
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Peptide fragments- degraded to a.a. by nonspecific proteases
Ubiquitin- recycled to be tagged onto the next protein for degredation |
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What degrades dietary protein into polypeptides and amino acids in the stomach?
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Pepsin in the stomach
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What is secreted from the pancreas that aids in digestion of proteins?
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Trypsinogen, Chymotrypsinogen, proElastase, procarboxypeptidase
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What converts the pancreatic enzymes into their active forms?
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enteropeptidases in the small intestines
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What enzymes are secreted from the small intestines that finalize the digestion of proteins?
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Amino-peptidases and di/tri-peptidases
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What is required for a.a. transport from EC space into cells?
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ATP
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How many a.a. transport systems are there?
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7
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What 2 systems have common transport systems for a.a. uptake?
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Small intestine, proximal tubule of the kidney
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Why is cystinuria?
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A disorder of the proximal tubule's reabsorption of filtered cystine and basic a.a. (ornithine, arginine, lysine)- COAL which leads to accumulation of cystine in urinary tract which forms stones
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What is COAL transporter?
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Transports cystine, ornithine, arginine, lysine
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What is the treatment for cystinuria?
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Oral hydration
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What is transamination?
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Moving NH3 group from one a.a. + keto-acid to form glutamate + another keto-acid
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What is alanine transferase?
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catalyzes alanine + pyruvate = alpha-ketoglutarate + glutamate
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What is aspartate aminotransferase?
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catalyzes aspartate + keto-acid1 to glutamate + keto-acid 2
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What are examples of keto-acids?
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oxaloacetate, alpha-ketoglutarate, pyruvate
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What is PLP?
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Pyridoxal phosphate
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What is the source of PLP?
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Active form of vit B6
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What does PLP do?
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It is the cofactor in transamination reactions
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Where does transamination occur?
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In the liver
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Is transamination reversible or not?
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Yes. It is reversible
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What are the 2 steps required for amino acid disposal?
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1. transamination with an aminotransferase
2. Oxidative deamination with glutamate dehydrogenase |
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What are the steps required for synthesis of amino acids?
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1. Reductive amination of alpha-ketoglutarate to glutamate
2. Transamination of glutamate to make alpha-amino acid from alpha ketoacid |
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What does oxaloacetate become when an amino is added?
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Aspartate
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What does glutamate become when an amino group becomes an O=?
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alpha-ketoglutarate
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What does alanine become when an amino group becomes O=?
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pyruvate
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What does glutamate dehydrogenase do? What cofactors are used?
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transfers and amino removes the amino group from glutamate to produce alpha-ketoglutarate + NH3
Cofactors: NAD+ (or NADP+) becomes NADH (NADPH) |
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How is glutamate formed from alpha-ketoglutarate?
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reductive amination via glutamate dehydrogenase
adds an NH3 group to alpha-ketoglutarate and reduces the O= bond with NADPH (or NADH) |
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How is nitrogen transported to the liver?
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In the blood attached to alanine and glutamine
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What happens to nitrogen in most tissues?
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Glutamine synthase takes NH3 + ATP and forms Glutamine + ADP
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What happens to nitrogen once in the liver?
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Glutaminase takes Glutamine + H20 and forms glutamate + NH3
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What is the glucose alanine cycle?
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Alanine aminotransferase converts pyruvate to alanine in the muscles (and glutamate to alpha-ketoglutarate), the alanine goes from the muscle to the liver where alanine aminotransferase converts it to pyruvate and pyruvate to glucose, which then goes back to the muscle
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What happens to ammonia once in the liver?
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It is detoxified into urea via Urea Cycle
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How much ammonia should be allowed in the blood?
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30-60 umol/L
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What are the sources of NH3?
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1. AAs
2. Glutamine 3. Bacterial urease 4. Amines 5. Nucleotides |
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How is NH3 found in circulation?
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1. Urea
2. Glutamine |
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Where is urea produced?
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Liver
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Where is urea transported to?
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Kidneys for excretion
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What provides the carbon atom of urea?
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CO2
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What is the requirement for carbamoyl phosphate synthetase I? How does it work?
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N-acetyl-glutamate
Allosteric activator |
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How is N-Acetylglutamate formed?
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Glutamate + AcCoa via synthase forms N-acetylglutamate + CoA
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How is the N-acetylglutamate converted back to glutamate?
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N-acetylglutamate via hyrolase forms acetate + glutamate
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What is an upregulator of synthase in the conversion of glutamate to N-acetylglutamate?
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Arginine
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What is normal serum ammonia levels?
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5-50 uM
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What are the causes of hyperammonemia?
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1. Genetic defects of urea cycle enzymes
2. Liver disease |
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What is hyperammonemia?
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Serum NH3 levels > 1,000 uM
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What are the symptoms of hyperammonemia?
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Toxic to CNS: slurred speech, tremors, somnolence, vomitting, cerebral edema, blurred vision, coma, death
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What can be done for a patient with a deficiency in CAP synthetase I?
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Tx with phenylbutyrate
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What does Tx with phenylbutyrate do for a patient with deficiency in CAP synthetase I?
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Converts NH3 to a form that can be excreted
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What does alanine aminotransferase (ALT) and aspartate aminotransferase (AST) indicate?
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Liver disease bc they have leaked from damaged hepatocytes into the blood
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Why is asparaginase injections used?
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To rid the blood of asparginine, which is an essential nutrient for cancer cells
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