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26 Cards in this Set
- Front
- Back
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Three conditions where amino acids are oxidized for energy
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1) Low carb diet rich in excess protein (e.g., Atkins)
2) Starvation 3) Diabetes |
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When a protein is broken down for energy, where does most of the energy come from?
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Oxidation of Alpha Keto Acids
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First step of digestion
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chewing/mixture with saliva
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Functions of saliva
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Bolus formation
Lubrication Dissolves food (amylase) Aids in taste Tissue repair - epidermal growth factor in salive Protection Aids in speech VERY IMPORTANT biological fluid |
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What do parietal glands secrete?
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Parietal glands secrete HCl to drop pH
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What stimulates the parietal glands?
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Gastrin
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What stimulates the chief cells to produce pepsinogen?
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Gastrin
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What does pepsin do?
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Pepsin is the active form of pepsinogen.
It cleaves proteins on the AMINO-terminal side of aromatic residues tyrosine, phe, and trp. |
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What happens when the contents pass into the small intestine?
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Pancreas secretes bicarb to neutralize the acid
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What stimulates the conversion of pepsinogen to pepsin? Where does this take place?
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The H+ in the stomach
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What does secretin do? Where is it released?
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Produced in duodenum.
It inhibits gastric motility and emptying. Stimulates pancreas to release bicarbonate ions. Stimulates gall bladder to secrete bile. |
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What stimulates the conversion of trypsinogen --> trypsin?
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Enteropeptidase
aka enterokinase |
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What other enzymes does trypsin activate?
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Chymotrypsin (from chymotrypsinogen)
Elastase (from proelastase) Carboxypeptidase (from procarboxypeptidase) |
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What does chymotrypsin cleave?
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The carboxy side of aromatic a.a. (Phe, Tyr, and Trp)
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What does elastase cleave?
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Proteins at bonds where carboxyl group is contributed by small side chain amino acids (alanine, glycine, serine).
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What do carboxypeptidases cleave?
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"Broad spectrum" making multiple hits on remaining small peptides
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Where does trypsin cleave proteins?
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Carboxy terminal side of Lysine and Arginine
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Essential amino acids
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Phenylalanine
Valine Tryptophan Threonine Isoleucine Methionine Histidine Arginine Lysine Leucine PVT TIM HALL |
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Three general reactions responsible for A.A. metabolism
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1) involving amino group
2) involving carboxy group 3) involving methyl group |
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Transamination
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Catalyzed by aminotransferases/transaminases.
Pyridoxal phosphate (PLP) is cofactor for these reactions. Amino group from one amino acid is transfered to the alpha carbon of alpha-ketoglutarate leaving behind the alpha keto acid analog of the amino acid. |
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Pyridoxal Phosphate (PLP)
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Enzyme that catalyzes transamination.
Forms a Schiff linkage with the donor amino acid. The aldehyde form of PLP gets converted to the aminated form. Then the aminated form donates its amino group. |
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Deamination: Oxidative
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Glutamate transported from cytosol to mitochondria where it undergoes oxidative deamination catalyzed by l-glutamate dehydrogenase and alpha ketoglutarate and ammonia are produced.
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L-glutamate dehydrogenase
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Catalyzes oxidative deamination
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Deamination: Non-oxidative
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Dehydration reaction with no net change in oxidation but results in the release of NH3.
Example: Serine is converted to pyruvate and NH3 |
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De<b>amid</b>ation
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Direct removal of an Amide functional group.
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How are nitrogenous wastes ultimately eliminated?
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as either Ammonia or Urea
Would expect to see more ammonia in people with liver problems, and urea in healthy ppl |
