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biochem black6

amino acid metabolism stack 1

QuestionAnswer
Where is protein catalyzed in the body? primarily liver and skeletal muscles
What is the first step of breaking down proteins? proteins are hydrolyzed to their amino acid subunits by stomach and pancreatic proteases
What is transamination? alpha-amino group is removed from the amino acid by a transaminase. This produces alpha-ketoacids
What happens to the alpha-ketoacids in liver? metabolized to glucose via gluconeogenesis acetyl-CoA and Ketone bodies
What is produced and secreted by the serous cells of the stomach? Its role? Pepsinogen (a zymogen) which is converted by HCL to pepsin, an endopeptidase
What role does pepsin play in the stomach? It hydrolyzes large, denatured proteins to medium and small oligopeptides
Once proteins reach the intestine what chemical storm occurs? What initiates the storm? zymogens (chymotrypsinogen, trypsinogen and other) from the pancrease arrive at the signal of cholecystokinin (CCK).
What happens to trypsinogen? What effect does this have on other zymogens? trypsinogen converts to active form, trypsin. Trypsin cleaves to activate all the other zymogens.
Where do amino acids go when they are broken down from proteins in the intestine? amino acids absorbed by the intestinal mucosal cells and released into portal system
What is the concentration difference between intracellular and extracellular amino acids? Extracellular low, Intracellular high
How is the concentration gradient maintained? ATP-dependent transport systems
If you do not produce sufficient pancreatic secretions what condition can result? steatorrhea (lipid in the feces) and undigested protein in feces
What causes celiac disease? malabsorption resulting from immune-mediated damage to small intestine in response to ingestion of gluten
What inherited disorder results from a defective ATP-dependent amino transport system? cystinuria
How does cystinuria clinically present itself? What is the etiology? kidney stones caused by the precipitation of cysteine.
What amino acids appear in the urine with cystinuria? COAL - cysteine, ornithine, arginine and lysine
How does 90% of the nitrogen that enters the body via diet, exit the body? urea = 90%
What fills the amino acid pool? hydrolyzed dietary protein and body protein from muscle and general turnover
What is the significance of PEST? PEST are Pro-Glu-Ser-Thr, or proline, glutamin, serine and threonine. Proteins with these series have a very short half-live
Which proteins turn-over quicker, intra or extra cellular? intracellular Extracellular such as collagen last from months to years
If we are in a well-fed state, how does our body prioritize the use of digested amino acids? synthesis proteins to replace rapidly turning over plasma proteins
What other things does the liver make from amino acids? purines, pyrimidines, heme groups (porphyrins), neurotransmitters
What happens to excess amino acids? metabolized into product to enter various pathways such as glycolysis and TCA for energy production/ATP synthesis
If we be hungry hippos, what happens to our amino acids? muscle proteins are broken down via proteolysis
What cycle allows amino acids from muscle to travel to liver in blood stream? Glucose-Alanine cycle: transamination to alpha-ketoacid. Nitrogen transfered to pyruvate which becomes alanine. Alanine goes to liver and switches back to pyruvate while the nitrogen group goes to alpha ketoglutate which become glutamate=glyconeogen..
What must happen in order to use an amino acid for fuel? The nitrogen group must be removed
What happens to all this nitrogen removed from amino acids? Most is disposed as urea, a little remains as ammonia
What four things does the Nitrogen atom play a crucial role in building and regulation? 1. purine and pyrimidine bases 2. peptide bonds in proteins 3. heme groups and cytochromes 4. neurotransmitters
When alpha-keto acids enter the TCA cycle what are the final products? CO2, H2O, ATP
Liver enzymes convert nitrogen groups to urea from what compounds? aspartate, ammonia and carbon dioxide
What is the most common inborn error of amino acid metabolism that causes mental retardation? Phenylketonuria due to phenylalanine hydroxylase deficiency so phenylalanine cannot be broken down to tyrosine - it builds up to toxic levels
How might a person with PKU look different? hydroxylation of tyrosine by tryosinase is the first step in production of melanin. High phenylalanine inhibits it.
What rare disease involves homogentisic acid oxidase deficiency? Why? Symptoms? Alcaptonuria, problem in the degradation of tyrosine. black diaper syndrome, large joint arthritis and black ochroniotic pigmentation of cartilage - crippling arthritis
If my branched-chain alpha-keto acid dehydrogenase don't get the job done what strange disease occur in me? Problem? Maple Syrup Urine D. due to inability to decarboxylate leucine, isoleucine and valine It can be lethal!
What will a B12 deficiency cause? Why? anemia - cannot make heme groups?
If you are low on B12, B6 and folate what pathway is in jeopardy? What condition will occur? treatmen? Homocystinuria - inherited, autosomal recessive homozygous folks will have displace lens of eye, mental retard, skeletal abnormalities Treat with B vitamins
A patient is slurring their speech, vomiting, having tremors, blurred vision and then collapses into coma. What could be the amino acid metabolism problem? Hyperammonemia
What are the two enzymes that must be known for hyperammonemia? 1. carbamoyl phosphate synthetase (CPSI) 2. Ornithine transcarbamoylase
Alcoholics and folks with hepatisis aquire a deficiency in which enzyme that brings on hyperammonemia? carbamoyl phosphate synthetase
How does a deficiency in Ornithine transcarbamoylase develop? X-linked recessive, and the most common of all the urea disorders
Four key enzymes must be known for Nitrogen removal and excretion, what they be? 1. glutamine synthetase; 2. glutaminase; 3. transaminases: ALT & AST; 4. Glutamate Dehydrogenase
What is one way to detoxify ammonium,but requires energy in the form of ATP? amination: glutamate + ammonium NH4 + ATP = glutamine + ADP + Pi catalyzed by glutamine synthase!!!
The kidneys actually use an enzyme to produce ammonium and assist in acid-base balance. What is the enzyme and reaction? glutaminase catalzyes glutamine + H2O = glutamate + NH4+
Luchia loves two enzymes that are aminotransferases..what are they? ALT: alanine aminotransferase AST: aspartate aminotransferase
How are ALT and AST named? Why? Named based on the starting amino acid, alanine or aspartate because the end product of both reactions is alpha-ketoglutarate
Why are ALT and AST useful for the clinician? They are intracellular enzymes. physical trauma or disease cause cells to lyse releasing them.
What are some diseases or conditions in which AST and ALT should be elevated in the blood? Liver disease:viral hepatitis, toxic injury (alcoholism), prolonged circulatory collapse Non-liver: MI, muscle disorders
Urea synthesis actually requires ammonia ions. How can this be generated? glutamate dehydrogenase can catalyze reversible deamination from glutamate to alpha-ketoglutarate which release NH4 ions
What are the two transport mechanisms for moving ammonia? 1. glutamine synthetase 2. glucose-alanine pathway
How does the glutamine synthetase mechanism work to move nitrogen groups (ammonia) to the liver from peripheral tissue? glutamine synthetase combines ammonia + glutamate = glutamine: nontoxic, travels in blood to liver. In liver it can be cleaved by glutaminase to release the NH$
What is the transport mechanism used mostly by muscles to get rid of ammonia? transamination: NH3 from glutamate put on pyruvate = alanine. alanine travels in blood to liver. switched back to pyruvate by ALT. ALT also puts the NH3 on alpha-ketoglutarate. Glutamate dehydrogenase then takes it off to send it for urea formation.
What enzyme prevents hyperammonia? glutamine synthetase binds NH3 to glutamate to make non-toxi glutamine
When glutamine travels to the kidney, what enzyme removes the NH3 for excretion in urine? glutaminase
If glutamine goes to the intestine, what enzyme kicks free the NH for export (via the portal vein) for trip liver and urea synthesis? glutaminase
Created by: El Diablo on 2010-02-13



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