Term
| List the sources of free amino acids in the body |
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Definition
-degradation of ingested protein
-biosynthesis of some amino acids
-degradation of endogenous protein |
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Term
| Define the terms essential and non-essential amino acids |
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Definition
essential amino acids- amino acids that must be supplied in the diet
non-essential amino acids- amino acids that can be synthesized in the body from precursor molecules |
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Term
| **Predict whether biosynthesis of amino acids is sufficient to allow net synthesis of protein when dietary protein is not available |
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Definition
| yes, but certain amino acids are essential and need to be obtained through diet |
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Term
| Describe the "turnover" of endogenous proteins, indicating the range of half-lives of endogenous proteins and the amount of protein turned over each day |
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Definition
-Most proteins are continuously degraded and synthesized
- turnover rates vary for individual protein in different tissues (regulartory proteins tend to have faster rates)
-Half-lives range from a few minutes to days |
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Term
| Describe how free amino acids are utilized |
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Definition
-synthesis of endogenous protein
-precursors for the synthesis of other biomolecule (purines and pyrimidines)
-for energy production (w/excretion of amino group as urea) |
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Term
| Predict the consequences of a protein-free diet |
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Definition
| Body protein will be degraded because the body degrade or loses the equivalent of 55g of protein a day (for a 70kg adult), even in the absence of dietary protein |
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Term
| Indicate how much protein must be present in the diet to maintain body protein |
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Definition
-A daily intake of 55g per 70kg of body weight
- Recommended Dietary Allowance - 0.79 g/kg |
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Term
| Indicate what happens to dietary protein that is in excess of the RDA |
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Definition
| -excess amino acids are degraded not, not stored |
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Term
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Definition
- Nitrogen Balance= Nitrogen ingested - Nitrogen excreted
-for NB=0; nitrogen ingested (primarily as protein) = nitrogen excreted (primarily as urea), this is nitrogen equilibrium |
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Term
| Be able to predict the nitrogen balance status for various physiological situations |
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Definition
Positive nitrogen balance -Ingestion >excretion; pregnant women, body builder's, growth in children ---nitrogen accumulates due to increased protein synthesis
Negative nitrogen balance -Ingestion <excretion; starvation, protein malnutrition, trauma, infection, cancer, burn injury, sepsis, and surgery ---muscle mass decreases due to decreased protein synthesis |
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Term
| Indicate the role of the two processes of amino acid degradation |
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Definition
-Removal of nitrogen to form urea: ammonia can be toxic to body
-Degradation of carbon skeletons: provides energy |
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Term
| Describe the transamination reaction in terms of the types of substrates, products, and cofactor that are involved |
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Definition
substrates: alanine (donor); alpha-ketoglutarate (acceptor)
products: pyruvate (acceptor); glutamate (donor)
enzyme:alanine transaminase
cofactor: pyridoxal phosphate (derivative of B6) |
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Term
| Indicate which amino acid serves as a reservoir of nitrogen following transaminase reactions involving other amino acids |
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Definition
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Term
| Indicate how glutamate is converted to aspartate and ammonia |
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Definition
aspartate- when glutamate levels are high, aspartate is being removed to make urea and the reaction is driven to the right; transaminase reaction
ammonia: increased glutamate and decreased ammonia cause reaction to go towards the production of ammonia; oxidative deamination |
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Term
| Indicate the organ responsible for urea biosynthesis |
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Definition
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Term
| Urea Cycle: Intermediates, primary regulated enzyme and its allosteric activator, name of the enzyme that produces urea from arginine |
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Definition
-Intermediates:Carbamoyl phosphate and citrulline (both made in mitochondria) arginiosuccinate and arginine (cytosol)
- carbamoyl phosphate synthetase I with N-Acetylglutamate as allosteric activator
-arginase |
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Term
| Predict the effect of a high protein diet on the rate of urea production |
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Definition
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Term
| Indicate which two amino acids are the major carriers of nitrogen to the liver |
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Definition
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Term
| Describe the consequences of decreased urea production |
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Definition
- urea production is used to detoxify ammonia, so less production means that there are high levels of ammonia in the system
- Hyperammonenia leads to Hepatic coma- acquired or genetic |
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Term
| Define glucogenic and ketogenic |
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Definition
-glucogenic-yields TCA cycle intermediates or pyruvate that can be used for gluconeogenesis
-ketogenic- yields acetyl CoA, acetoacetyl CoA, or acetoacetate |
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Term
| Indicate how the transient net synthesis and degradation of protein is thought to be regulated in muscle |
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Definition
- In the Fed state: amino acids and insulin stimulate protein synthesis, while insulin inhibits protein degradation
-Overnight fast: decrease in amino acids and insulin leads to the degradation of protein to free amino acids |
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Term
| Indicate the function of amino acids released during an overnight fast |
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Definition
| -use by the liver for gluconeogenesis (glucagon stimulates uptake of amino acids in the liver) |
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