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140 Cards in this Set
- Front
- Back
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what happens to the degradation products of amino acids?
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feed into the TCA cycle
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when is skeletal muscle broken down? when are amino acids used to create energy?
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starvation conditions
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why is arginine considered an essential amino acid if it can be created via the urea cycle?
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not enough is produced in the urea cycle to use for protein synthesis
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what amino acid is required for the synthesis of cysteine?
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methionine
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what is required for the synthesis of tyrosine?
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phenylalanine
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what are glucogenic amino acids?
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amino acids which can be degraded into compounds that can be specifically used as carbon skeletons for gluconeogenesis
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what are ketogenic amino acids?
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amino acids which can be degraded into compounds that can only be used to generate ketone bodies
only acetoacetate or acetyl-CoA |
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which amino acid is essential in nitrogen homeostasis in the body?
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glutamate
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what is AST?
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aspartate transaminase (AST)
Serum glutamic oxaloacetic transaminase (SGOT) |
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what is ALT?
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alanine aminotransferase (ALT)
Serum glutamic pyruvic transaminase (SGPT) |
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what is indicated by high levels of AST or ALT?
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liver cell damage
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what four amino acids are interconvertable?
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aspartate
glutamate asparagine glutamine |
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what enzyme converts glutamate to aspartate?
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AST
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what enzyme converts aspartate to asparagine?
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asparagine synthetase
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what enzyme converts asparagine to aspartate?
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asparaginase
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what enzyme converts glutamate to glutamine?
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glutamine synthetase
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what enzyme converts glutamine to glutamate?
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glutaminase
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what enzyme converts pyruvate to alanine?
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ALT
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what enzyme converts glutamate to alpha-ketoglutarate?
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ALT
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what amino acid is interconvertable with serine?
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glycine
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what is serine derived from?
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3-phosphoglycerate
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what is the first step of serine catabolism?
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conversion to glycine
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what is derived from serine in addition to glycine?
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choline
ethanolamine |
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what is required for the conversion from glycine to serine?
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methylene tetrahydrofolate
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what is required for the conversion from serine to glycine?
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tetrahydrofolate
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what enzyme catalyzes conversion of serine to glycine and back?
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serine/glycine hydroxymethyltransferase
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what enzyme is used to convert glycine to CO2 and ammonia?
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glycine decarboxylase
(aka glycine cleavage complex) |
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what is caused by deficiency of glycine cleavage complex?
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nonketotic hyperglycinemia
leads to severe mental retardation |
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how is glycine involved in the nervous system?
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inhibitory neurotransmitter
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what vitamin is important in nitrogen metabolism?
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folate
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how is tyrosine made in the body?
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hydroxylation of phenylalanine
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what is tyrosine degraded to?
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fumarate
acetoacetate |
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what is the first enzyme in the catabolism of tyrosine?
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homogentisate oxidase
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what is caused by lack of homogentisate oxidase?
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Alkaptonuria
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what happens in alkaptonuria?
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urine turns brown/black on exposure to air
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what is the first step in the catabolism of phenylalanine?
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conversion to tyrosine
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what is ocranosis? what causes it?
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black/blue discoloration of tissues, particularly sclera of eyes
alkaptonuria causes it |
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with patients with ocranosis, what are they at increased potential for?
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arthritis
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what enzyme converts phenylalanine to tyrosine?
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phenylalanine hydroxylase
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what is caused by a defect in phenylalanine hydroxylase?
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phenylketonuria (PKU)
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what is required for the conversion of phenylalanine to tyrosine?
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tetrahydrobiopterin
continuous renewal of tetrahydrobiopterin supply from dihydrobiopterin |
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what enzyme catalyzes the reduction of dihydrobiopterin to tetrahydrobiopterin?
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dihydropterine reductase
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what is hyperphenylalanemia?
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excess phenylalanine in the blood
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what two things, other than PAH deficiency, could cause hyperphenylalanemia?
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defective biosynthesis of biopterine
defect in dihydrobiopterine reductase |
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what are the three common metabolites in the blood of PKU patients?
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phenylpyruvate
phenyllactate phenylacetate |
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what phenylalanine metabolite gives urine a mousy odor?
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phenylacetate
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what phenylalanine metabolites result in a disruption of energy production? how?
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phenylpyruvate and phenyllactate
divert lactate and pyruvate into non-gluconeogenic pathways |
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what can cause defects in the CNS in PKU?
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disrupted energy production caused by diverted lactate and pyruvate
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what is the sulfur donor for cysteine?
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methionine
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what is SAM?
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s-adenosyl methionine
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how is SAM converted to SAH?
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transfer of -CH3
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what is the principal -CH3 acceptor of SAM conversion to SAH?
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norepinephrine
(forms epinephrine) |
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what is formed when adenosine is removed from SAH?
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homocysteine
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what forms cystathionine?
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homocyteine
serine |
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what enzyme yields cysteine and a-KB from cystathionine?
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cystathionase
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what is alpha-KB?
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alpha-ketobutyrate
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when is homocysteine metabolized to alpha-KB, ammonia, and Hydrogen sulfide?
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when need for energy is higher than need for cysteine
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what is SAH?
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s-adenosylhomocysteine
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what is required for production of norepi and epi?
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S-adenosyl methionine
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what possible relation does homocysteine have with cardiovascular disease?
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it is a negatively charged molecule, which triggers the activation of coagulation cascade, causing hypercoagulopathy
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why is it thought that adding B12 would would decrease the risk of cardiovascular disease caused by high homocysteine levels?
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should drive homocysteine to methionine, but doesn't
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what can be produced by two moles of cysteine? what catalyzes this reaction?
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pyruvate and thiocysteine
cystathionase |
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what can be produced by cysteine?
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pyruvate
thiosulfate |
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what is used to detoxify cyanide?
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thiocysteine
thiosulfate |
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how can cysteine make bile acids more water-soluble?
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it is converted to taurine, which conjugates bile acids and makes them more water-soluble
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why is cysteine (or its byproducts) not helpful in combating deliberate cyanide poisoning?
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too slow
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where is the metabolism of branched chain amino acids most important?
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skeletal muscle
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what is the benefit of catabolizing branched chain amino acids?
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lots of NADH and FADH2 produced
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what is the first step in the catabolism of all three branched chain amino acids?
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branched chain alpha-ketoacid dehydrogenase
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what are the three branched chain amino acids?
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valine
isoleucine leucine |
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what is caused by a deficiency in branched chain alpha-ketoacid dehydrogenase?
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maple syrup urine disease (MSUD)
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how can you tell if someone has maple syrup urine disease?
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if their urine smells like maple syrup
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what is related to maple syrup urine disease?
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catabolism of branched chain amino acids
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what is an intermediate in both the urea cycle and the synthesis of polyamines?
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ornithine
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what is the purpose of polyamines? why?
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stabilize DNA
polyamines have several amino groups, giving them a highly positive charge, which stabilizes the negative charge of DNA |
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what amino acid is converted to both ornithine and proline?
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glutamate
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in what condition is glutamate converted to ornithine more prevalent than to proline?
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ornithine would be preferred if the body were in a highly catabolic state and the liver was being bombarded with huge amounts of alanine
(to keep urea cycle going efficiently) |
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in what condition is glutamate conversion to proline more prevalent than to ornithine?
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proliferative growth cell
(for amino acid biosynthesis) |
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what is the amino acid precursor for carnitine?
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lysine
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what deficiency causes formiminoglutamate to be excreted in urine following a test dose of histidine?
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folate deficiency
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what is the precursor for histamine?
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histidine
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what enzyme catalyzes the conversion of histidine to histamine?
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histidine decarboxylase
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what is the enzyme in histidine catabolism which commonly has a defect?
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histidase
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catabolism of which amino acid yields glutamate and N5-formiminotetrahydrofolate?
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histidine
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what neurotransmitters are derived from tyrosine?
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DOPA
Dopamine Norepinephrine Epinephrine |
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what enzyme in tyrosine metabolism requires tetrahydrobiopterine?
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tyrosine hydroxylase
which is first step to producing all NTs from tyrosine |
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what amino acid is the precursor for melanin synthesis?
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tyrosine
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what is required for synthesis of melanin from tyrosine?
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tyrosinase
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what is caused by a lack of tyrosinase?
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albinism
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what neurotransmitters are derived from tryptophan?
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serotonin
melatonin |
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what is the process of melatonin production?
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tryptophan -> serotonin -> melatonin
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where is serotonin found?
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90% in GI tract
10% in CNS |
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what is the order of serotonin effects prominently felt?
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cardiovascular system
respiratory system intestinal tract |
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what is the classic response of serotonin?
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vasoconstriction
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what are SSRIs?
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selective serotonin reuptake inhibitors
drugs such as prozac, etc. which reduce the reuptake of serotonin and are used as antidepressants |
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what is 5HT?
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5-hydroxytryptamine
(serotonin receptors) |
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how do serotonin receptors (5-HT) function?
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majority through adenylate cyclase or PLCgamma
only one (5HT3) is ion channel |
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in terms of G-protein coupled receptors, what does GI do? GS? GQ? GO?
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GI - inhibits cAMP production
GS - activates cAMP production GQ - activate PLCgamma GO - do other things |
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what neurotransmitter is involved in the diurnal rhythms such as sleep-wake cycle?
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melatonin
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from what is melatonin synthesized? where? when?
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tryptophan
pineal gland in the dark |
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how does melatonin function?
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inhibits synthesis and secretion of neurotransmitters (GABA, dopamine)
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what molecules are derived from ornithine and stabilize DNA during DNA replication?
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polyamines
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what are the two polyamines smelled in decaying flesh?
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putrescine
cadaverine |
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what is the earliest signal of cell division?
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ornithine decarboxylase activity
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what signals the synthesis of DNA binding proteins, spermine and spermidine?
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ornithine decarboxylase activity
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what is creatine used for?
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high energy phophate store in skeletal muscle and brain
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what is creatinine?
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non-enzymatic by-product of creatine
excretion serves as measure of renal function |
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what enzyme converts creatine to creatine phosphate?
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creatine kinase
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what conditions effect a change in the creatinine clearance rate?
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kidney disease/damage
won't change based on weight |
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why is there a constant amount of creatinine in the urine?
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creatine spontaneously degenerates into creatinine and is excreted
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what enzymes are used to measure and indicate cardiac insult?
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creatine phosphokinase
lactate dehydrogenase |
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what is the other name for creatine phosphokinase?
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creatine kinase
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what causes elevated levels of CPK-1?
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brain cancer
brain injury electroconvulsive therapy pulmonary infarction seizure |
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when do CPK-2 levels rise?
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3-6 hours after heart attack
level peaks at 12-24 hours returns to normal 12-48 hours after tissue death |
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what causes CPK-2 levels to rise?
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heart attack
electrical injuries heart defibrillation heart injury (from car accident) myocarditis (inflammation of heart muscle) open heart surgery |
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what causes higher than normal CPK-3 levels?
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muscle injury or muscle stress
crush injuries muscular atrophy muscular dystrophy myositis (skeletal muscle inflammation) receiving lots of IM injections recent EMG study recent seizures recent surgery strenuous exercise |
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what conditions don't lead to raised CPK-2 levels?
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chest pain from angina
pulmonary embolism congestive heart failure |
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when does lactate dehydrogenase concentration increase in the blood?
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6-12 hours after MI
peak at 48 hours stays elevated 4-14 days post-MI |
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why is lactate dehydrogenase use to indicate MI discouraged?
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non-specificity
raised in muscular dystrophy myoglobinuria leukaemia pernicious anemia megaloblastic anemia hemolytic anemia renal disease generalized carcinoma |
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which isozyme of lactate dehydrogenase is elevated in response to MI? to liver damage?
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LD1
LD5 |
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what is glutathione's most important role?
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antioxidant, particularly in red blood cells
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what are the roles of glutathione?
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antioxidant
reductant make drugs more soluble amino acid transport across cell membrane peptidoleukotrienes enzymatic reactions |
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from what is NO produced?
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arginine
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what enzyme produces NO from arginine?
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nitric oxide synthase (NOS)
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what is NOS dependent on?
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NOS = nitric oxide synthase
NADPH |
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what are the three isozymes of NOS in mammals?
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neuronal nitric oxide synthase (nNOS)
inducible nitric oxide synthase (iNOS) endothelial nitric oxide synthase (eNOS) |
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where is nNOS enriched?
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CNS
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where is iNOS enriched?
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white cells
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where is eNOS enriched?
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endothelial cells
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which isozymes of NOS contain calmodulin subunits? which NOS isozymes function by binding of calcium?
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all have calmodulin subunit
only nNOS and eNOS function by binding calcium |
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how do many vasodilators work?
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release intracellular store of calcium
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how is iNOS stimulated?
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expression of gene for iNOS is induced in response to stimuli which activate monocytes, etc.
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how does NO get into cells?
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rapidly diffuses across cell membrane
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what happens in smooth muscle cells as a function of NO?
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activates guanylate cyclase, which produces cGMP from cGTP
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what is PKG?
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cGMP-dependent protein kinase
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what activates PKG?
what effect does this have? |
cGMP
induce smooth muscle cell relaxation |
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what two isozymes of nitric oxide synthase are constitutively expressed?
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nNOS
eNOS |
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what roles does NO have?
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regulation of blood coagulation
inhibits platelet aggregation inhibits neutrophil adhesion to endothelium |
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what does overproduction of NO via iNOS lead to?
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septic shock
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what does LPS induce (in relation to NO)?
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iNOS synthesis
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