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Where is protein catalyzed in the body?
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What is the first step of breaking down proteins?
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biochem black6
amino acid metabolism stack 1
| Question | Answer |
|---|---|
| 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
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