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200 Cards in this Set
- Front
- Back
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what do kinases/phosphatases do?
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phosphate group transfer/removal
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what do dehydrogenases do?
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redox
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what do isomerases do?
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rearrangement
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what do lyases do?
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cleavage and add a water molecule
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what do synthases do?
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condensation (remove water)
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what organ can't use fatty acid synthesis?
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brain
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what are the dietary fuels?
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carbohydrates (sugar and starch), lipids (fats), proteins (amino acids)
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when are amino acids oxidized for energy?
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normal protein turnover, starvation/diabetes mellitus (uncontrolled), protein rich diet (Atkins' diet)
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what does the body do for fuel in the event of starvation of uncontrolled idabetes?
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break down your own amino acids to make glucose, which is a muscle-breaking event
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what is nitrogen balance?
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there intake is approximately equal to loss of nitrogen in healthy adults
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what is a positive nitrogen balance?
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intake is greater than loss of nitrogen; this may happen in growing children, preganancy, illness/trauma recover
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what is a negative nitrogen balance?
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loss is greater than intake; may occur during starvation.
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what leads to muscle-wasting metabolism?
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insufficient dietary supplies of a single essential amino acid, which may limit protein synthsis
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what does ureotelic mean?
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excreting amino nitrogen in the form of urea
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which animals are ureotelic?
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terrestrial animals (humans)
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what is ammonotelic?
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excreting amino nitrogen as ammonia.
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what animals are ammonotelic?
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bony fishes
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what does uricotelic mean?
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excrete amino nitrogen as uric acid
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what animalsa re uricotelic?
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birds and reptiles
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what enzyme starts the activity of breaking down proteins?
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pepsin
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what begins the breakdown of carbohydrates?
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amylase
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why does the stomach have a low pH?
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helps denature non-covalent bonds in proteins we eat
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what is the end result of digestion?
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chyme
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what secretions initiated by the CNS are important in digestion?
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acetylcholine
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what does atropine, probanthine do?
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blocks acetylcholine interaction with muscarinic receptors
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what does cimetidine (tagamet) or ranitidine (zantac) do?
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block histamine interaction with H2 receptors
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what does the intestinal mucosa produce?
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2 hormones, 1 enzyme
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what 2 hormones does the intestinal mucosa produce?
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cholecystokinin and secretin
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what enzyme does the intestinal mucosa produce?
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enteropeptidase
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what does cholecystokinin do?
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secretes bile salts from the gall bladder
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what does secretin do?
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secretes zymogens and HCO3 from the exocrine pancreas?
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what does enteropeptidase do?
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activates trypsinogen, which activates trypsin, which activates secretion of zymogens.
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what is the precursor of bile salts?
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cholesterol
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what do secretory cells of the exocrine pancreas secrete?
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zymogens and HCO3
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what is the end result of exocrine pancreas digestion?
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single amino acids
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how do amino acids get transported to the liver?
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portal vein
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where is the highest concentration of glutamine in the body?
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blood stream
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what is an example of a bioactive amine?
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tyrosine
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what happens to amino acids that aren't needed for synthesis of new proteins or amino compounds?
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catabolized
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what are the products of amino acid catabolism?
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ammonia (NH4) -- converted to urea for excretion
a-keto acid carbon skeletons: converted to pyr, acCoA, or TCA cycle intermediates |
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what does transamination do?
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funnels amino group to Glu in tissues (Ala in muscles)
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how is additional NH4 removed froom amino acids during amino acid metabolism?
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oxidative deaminatio, picked up by Glu to form Gln
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What is the fate of Gln/Ala in amino acid metabolism?
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carried in bloodstream to the liver
*some Gln goes to the kidney to be used as a buffer |
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where is most NH4 removed during amino acid metabolism?
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in liver mitochondria
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what happens to ammonia once it is removed from the amino acid?
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converted to urea and excreted
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what happens to the carbon skeleton in amino acid metabolism?
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enters TCA cycle if tissue needs energy
-used for glyconeogenesis, or glycogen, or lipid synthesis to store energy |
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what are the four main steps of amino acid metabolism?
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1. peripheral tissues use transamination with aKG to funnel N to Glu
2. Glu snthase to produce Gln. Skeletal muscle transaminates with pyruvate to form Ala. Gln and Ala travel through bloodstream to liver 3. liver takes up Ala and Gln. N is removed via transaminatoin, glutaminase, and Glu DH rxns 4. urea is produced. Urea sent to kidney for excretion. |
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what is the glucose-alanine cycle in skeletal muscle?
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pyruvate from the skeletal muscle glucose metabolism is converted to Ala, sent to liver and converted back to glucose and sent back to muscle.
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What mus thappen before nitrogen metablism can occur?
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peripheral tissues send nitrogen to liver via glutamine or alanine.
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what is teh first step in nitrogen metabolism in peripheral tissues?
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TRANSAMINATION.
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what happens during transamination?
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the amino group of the amino acid is swapped for a carbonyl group of alpha-keto acid
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what enzyme is involved in transamination?
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transaminase
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what cofactor is used in transamination?
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pyridoxal phosphate (B6 derivative)
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what is the usual alpha-keto acid acceptor?
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a=ketoglutarate
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which amino acids can transaminate with a-KG?
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all amino acids except Lys, Thr, and Pro
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what is the general outline of the paired reaction of transamination?
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aspartate+ aKG -->aketo acid + Glutamate
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which forms of vitamin B6 are involved in transamination reactions?
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pyridoxal phosphate and pyridoxamine phosphate
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what is involved in a schiff's base reaction?
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a primary amine plus glucose -->aldimine (schiff base), which undergoes amadori rearrangement to get a ketoamine.
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what are the three a-keto acids and what do they transaminate to?
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a-ketoglutamate --> glutamate
oxaloacetate (aspartate) pyruvate (alanine) |
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which step is known as the bimolecular ping pong reaction?
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transamination
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what should you check blood serum for when doing medical diagnostics?
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CK = creatine kinase
GOT = glu-OAA transaminase ALT- Ala aminotransferase LDH- lactate dehydrogenase |
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what amino acids does transamination produce?
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alanin and glutamate
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what is the purpose of the second step in nitrogen metabolism?
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convert glutamate to glutamine via GLUTAMINE SYNTHASE
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what does glutamine synthase signal to the cell?
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nitrogen is not needed for protein, nucleotide, or other bioactive amine synthesis.
it tells the cell it can commit to disposing of nitrogen |
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what is the main repository for NH3?
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glutamine
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Is glutamine synthesis reversible?
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yes
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what is a major control point for nitrogen metablism?
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glutamine synthesis
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What are allosteric modifiers of glutamine synthase?
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amino acids, nucleotides, Nitrogen compounds
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what are covalent modifiers of glutamine synthase?
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1. adenylation via adenylate transferase inactivates the enzyme
2. couples amino acid metabolism to nucleotide metabolism 3. AT is regulated by another protein-- PII which is modified by uridylyation |
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what is the main carrier to send amino groups to the liver for export as urea?
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Glutamine (Gln)
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what is involved in liver deamination?
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nitrogens are to be removed fro glutamate to regenerate aKG and NH4 to be used in the urea cycle
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Where does the glutamate come from for the liver deamination step?
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Ala from muscle will transaminate with aKG to make Glu
Gln will have side chain nitrogen removed via glutaminase and become Glu |
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How does glutamate make products to enter hte urea cycle?
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1. transaminate with OAA to make Asp, which will be used in urea cycle
2. undergo oxidative deamination via glutamate dehydrogenase to regenerate aKG and NH4 which will be used in the urea cycle |
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what does hydrolic deamination do?
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uses water to exchange with NH2 in the conversion of glutamine to glutamate
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what is the use of glutaminase in kidneys?
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to supply ammonia for acid neutralization in urine
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what is the end result of oxidative deamination via glutamate dehydrogenase?
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a-KG + NH4+
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what happens to glutamate after hydrolic deamination?
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becomes a KG+ NH4 via glutamate dehydrogenase
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What happens in the urea cycle?
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nitrogen metabolism
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where is most ammonia converted to urea?
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liver
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what is needed for the urea cycle to occur?
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3 ATP, 4 high energy bonds
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where do the nitrogens that make up urea come from in nitrogen metabolism?
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1 N from NH4, 1 N from Asp
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where does the urea cycle take place?
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some parts in the cytosol, come parts in the mitochondria
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which organ is damaged if there is a high [BUN]?
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kidneys
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which organ is damaged if [ammonia] is high?
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liver
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what are the 3 nitrogen excretion products?
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urea, ammonia, uric acid
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how does NH4 leave mitochondrial matrix in the urea cycle?
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couples with Co2 to make carbamoyl phosphate
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what is the committed step for entry into the urea cycle?
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caramoyl phosphate formation
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what are the 3 main components of urea?
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Asp, CO2, NH4
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where does the first step of the urea cycle occur?
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mitochondrial matrix
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what enzyme catalyzes the first step of the urea cycle?
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carbamoyl phosphate synthetase I
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what organ and organelle does the urea cycle take place in?
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liver mitochondria
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how many ATP are required for the commited step of the urea cycle?
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2
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what is the cofactor for the first step of the urea cycle?
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N-acetylglutamate
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what does carbamoyl phosphate condense with upon entering the urea cycle?
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orthinine, to make citrulline
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where does citrulline go to continue the urea cycle?
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cytoplasm
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what condenses with citrulline in the urea cycle?
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asp
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what is the Asp + citrulline product cleaved into?
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arg and fumarate
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how does arg become urea?
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hydrolization by water
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what happens to orthinine after arginine becomes urea in the urea cycle?
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diffuses back into the mitochondria
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what is the immediate precursor for urea synthesis?
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arginine
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what happens when NH4 is in excess?
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aKG is siphoned from the TCA cycle for transamination to Glu for converstion to Gln for export to the liver
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what sends out nitrogen groups from the brain?
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glutamine
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elevated ammonia levels mean that NH4 processing...
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depletes the TCA cycle intermediate aKG, and thus NADH production
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what does a decrease in aKG in the brain mean?
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decreased ATP production
breain is highly ATP dependent |
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if ammonia is elevated in the brain, how does that affect GABA and osmotic balance?
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-depletes Glu and GABA
-build up of Gln increases intracellular osmotic balance, water enters astrocytes, brain swells |
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what do high levels of BUN indicated?
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kidney problems
(liver made urea, but kidney isn't excreting it) |
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what do high levels of nitrogen as free ammonia indicate?
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liver problems
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what do defects in urea metabolism usually cause?
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mental retardation, seizures, and/or coma
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how are defects in urea metabolism treated?
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control of diet, administration of detoxifying compounds
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what are the 2 major categories of the 20 amino acids?
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glucogenic and ketogenic
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what does glucogenic mean?
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TCA cycle intermediates that can be shunted to gluconeogenesis
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what does ketogenic mean?
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acetyl CoA derivates that can be used for ketone body synthesis
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how many amino acids are at least partically glucogenic?
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18/20
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how many amino acids are glucogenic and ketogenic?
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4/20
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which 4 amino acids are both glucogenic and ketogenic
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the 3 aromatics, and Ile
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which amino acids are purely ketogenic?
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leu and lys
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what does the breakdown of methionine result in?
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cystein
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what does the breakdown of phenylalanine result in?
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tyrosine
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what is the key in the interconversion of amino acids and carbohydrates?
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relatinoship between amino acids and a-keto acids
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what metabolites of amino acid metabolism are glucogenicc?
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pyruvate, oxaloacetate, a-KG, fumarate, propionyl CoA (succinyl CoA)
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what metabolites of amino acid metabolism are ketogenic
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acetoacetyl CoA, acetyl CoA
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where does priopnyl CoA (succinyl CoA) come from?
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long chain fatty acids with odd number of carbons
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what 3-carbon amino acids form pyruvate?
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alanin, serine, cysteine, tryptophan
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how does alanine form pyruvate?
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ala + aKG --> Glu + pyr
via alanine aminotrasferase |
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how does serine form pyruvate?
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with serine-threonine dehydratase, it forms pyruvate, NH4 and water
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how does cysteine for pyruvate?
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multistep pathway
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how does tryptophan form pyruvate?
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alanine + ring structures form pyruvate
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which amino acid forms pyruvate by transamination?
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alanine
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what is the four carbon a-keto acid?
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oxaloacetate
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what is the 3 carbone aketo acid?
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pyruvate
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what 4 carbon amino acids form oxaloacetate?
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asparginine, aspartate
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how does asparginine form oxaloacetate?
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it forms aspartate, which then can become OAA
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how does aspartate become OAA?
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Asp + aKG with the help of aspartate transaminase makes OAA + Glu
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what a keto acid does aspartate become?
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oxaloacetate
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what is the 5 carbon a keto acid?
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alpha keto glutarate
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what must amino acids first convert to before they can become alpha keto glutarate?
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glutamate
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what amino acids can convert to alpha keto glutarate?
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glutamine, proline, arginine, histidine, glutamate
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how does glutamine convert to glutamate?
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by glutaminase
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how does proline convert to glutamate?
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it goes to pyrroline-5-carboxylate, then to glu-gamma-semialdehyde, then to glutamate
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how does histidine go to glutamate?
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a multi-step pathway that require THF transfer
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how does arginine go to glutamate?
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first to orthinine, then to glu-gamma semialdehyde
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how does glutamate go to alpha keto glutarate?
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by combining with OAA and help with glutamate-OAA transaminase
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what is the amino acid precursor of a ketaoglutarate?
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glutamate
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which amino acid becomes glutamate by direct deamination?
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histidine
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which branched chain amino acid are metablized to CoA derivatives?
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valine, Isoleucine, leucine.
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what CoA derivative does Valine become?
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propionyl CoA
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what CoA derivative does Isoleucine become?
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propionyl CoA + acetyl CoA
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what CoA derivative does Leu become?
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acetoacetate + acetyl CoA
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what two amino acids can convert to propionyl CoA via aketobltyrate?
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methionine and threonine
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which branched chain amino acids shre the first steps of oxidation?
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val, ile, leu
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in which organ does transamination NOT occur?
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liver
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which disease is a disorder of branched chain a-keto acid dehydrogenase complex?
|
maple syrup urine disease
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how is propionyl CoA converted to succinyl CoA?
|
1st propionyl is carboxylated with propionyl CoA carboxylase and biotin to D-methylmalonyl CoA.
Then with methylmalonyl CoA mutase with cobalamin goes to succinyl CoA |
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what does deficiency of cobalamin cause?
|
pernicious anemia
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what vitamin is only synthesized by microorganisms?
|
vitamin B12/cobalamin
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what gastric protein binds to cobalamin in intestines, making it resistant to digestion?
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intrinsic factor
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what does a deficiency in vitamin B12 cause?
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pernicous anemia
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Where is vitamin B12 absorbed?
|
ileum
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where is vitamin B12 released and what does it bind to after being absorbed in the ileum?
|
bloodstream and binds to transcobalamin II (transport protein)
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what is a metabolic disease called caused by a defect in branched chain amino acid metabolism?
|
methylmalonic acidemia (MMA)
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what amino acids are strictly ketogenic?
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lysine and leucine
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what CoA derivative is Lys converted to?
|
acetoacetyl CoA
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what CoA derivative is leucine able to convert to?
|
acetylCoA and acetoacetate
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which amino acids are both glucogenic and ketogenic?
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phenylalanine, tyrosine, and tryptophan
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how does phenylalaine go to tyrosine?
|
via phenylalanine hydroxylase
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what enzyme is missing in PKU?
|
phenylalanine hydroxylase
|
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what enzyme was insrumental in the "1 gene 1 protein" hypothesis?
|
alkaptonuria
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what is phenylketonuria?
|
autosomal recessive disease
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how does one treat pKU?
|
low phenylalanine diet until adolescence
|
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what results from a lack of treatment of PKU?
|
severe mental retardation
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what is a cofactor in many hydroxylase rxns? what is it important in the production of?
|
tetrahydrobiopterin
neurotransmitters |
|
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what is alkaptonuria?
|
genetic disease
"ochronosis" arthritis-like symptoms |
|
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what is albinism? what does it result in phenotypically?
|
deficiency in tryosinase
decrease in melanin production |
|
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what is glycine converted to in bacteria?
|
first to serine, then to pyruvate
|
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what is glycine converted to in humans?
|
CO2 + NH4
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how is glycine converted to oxalate?
|
by D amino acid oxidase dehydration to glyoxylate. then reduced to oxalate
|
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what serves as a substrate for lactate dehydrogenase?
|
glyoxylate
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what is the major component of kidney stones?
|
calcium oxalate
|
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which orientation of amino acids are a major component of bacterial cell walls?
|
D amino acids
|
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what category, glucogenic or ketogenic are most amino acids?
|
glucogenic
|
|
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which amino acids produce both glucogenic and ketogenic products?
|
3 aromatics: Phe, Tyr, Trp
1 branched chain: Ile |
|
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which 2 amino acids are only ketogenic?
|
Leu, Lys
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which enzyme is important in transfer of CO2?
|
biotin
|
|
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which enzyme transfers carbons in various oxidation states?
|
terahydrofolate (THF)
|
|
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what enzyme transfers methyl group s(CH3)
|
S adenosylmethionine (SAM)
|
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what are the enzyme cofactors important in 1 carbon transfers?
|
biotin, THF, SAM
|
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what is the main function of cabalamin?
|
source of free radicals for proton exchanges
|
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how many reactions require cobalamin?
|
2, both involved in amino acid metabolism
|
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what ist he main function of biotin?
|
carries activated CO2; carboxylase reaction
|
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what is the main function of pyridoxine?
|
transaminations
|
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what is the common name of pyridoxine?
|
vitamin B6, PLP
|
|
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what is the main function of folate?
|
precursor of THF for methyl group transfers
|
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what is the common name of folate?
|
folic acid
|
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what is the main function of cobalamin?
|
MMACoA --> SucCoA;
homocys --> met |
|
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what is the common name of Cobalamin?
|
Vit B12
|
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what enzyme is defective in PKU?
|
phenylalanine hydroxylase
|
|
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what enzyme is defective in alkaptonuria?
|
homogentisate oxidase
|
|
|
what enzyme is defective in maple syrup urine disease?
|
branched chain amino acid DH
|
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what enzyme is defective in methylmalonic acidemia?
|
methyomalonyl CoA mutase
|
|
|
what enzyme is defective in homocystinuria?
|
cystathione synthase
|
