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BiochemistryCONVERSION OF AMINO ACIDS TO SPECIALIZED PRODUCTS > CONVERSION OF AMINO ACIDS TO SPECIALIZED PRODUCTS > Flashcards

CONVERSION OF AMINO ACIDS TO SPECIALIZED PRODUCTS Flashcards

1
Q

The entire glycine molecule becomes atoms

A

4, 5, and 7 of purines

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2
Q

The nitrogen and a-carbon of glycine are incorporated into the

A

pyrrole rings and the methylene bridge carbons of heme

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3
Q

constitutes a major fraction of the free amino acids in plasma

A

Alpha alanine

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4
Q

Present in coenzyme A

A

Beta alanine

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5
Q

Mammalian tissues form b-alanine from

A

cytosine, carnosine, and anserine

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6
Q

b-Alanine Also present as

A

b-alanyl dipeptides, principally carnosine

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7
Q

activate myosin ATPase, chelate copper, and enhance copper uptake

A

carnosine and anserine (Nmethylcarnosine

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8
Q

Participates in the biosynthesis of sphingosine, a component of sphingomyelin

A

Serine

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9
Q

the principal source of methyl groups in the body

A

S-Adenosylmethionine

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10
Q

Methionine It also contributes its carbon skeleton for the biosynthesis of the

A

3-diaminopropane portions of the polyamines spermine and spermidine

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11
Q

precursor of the thioethanolamine portion of coenzyme A and of the taurine

A

L. Cysteine

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12
Q

L-Cysteine is a precursor of the thioethanolamine portion of coenzyme A and of the taurine that conjugates with bile acids such as

A

Taurocholic acid

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13
Q

Decarboxylation of histidine to histamine is catalyzed by a broad-specificity aromatic

A

L-amino acid decarboxylase

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14
Q

catalyzes the decarboxylation of dopa, 5hydroxytryptophan, phenylalanine, tyrosine, and tryptophan

A

L-amino acid decarboxylase

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15
Q

Histidine to histamine

A

Histidine decarboxylase

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16
Q

formamidine donor for creatine synthesis and via ornithine to putrescine, spermine, and spermidine

A

Arginine

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17
Q

The 24-hour urinary excretion of creatinine is proportionate to muscle mass and is a useful indicator of kidney function

A

Creatinine

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18
Q

Glycine, arginine, and methionine participate in

A

Creatinine synthesis

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19
Q

Arginine is also the precursor of the intercellular signaling molecule

A

Nitric oxide

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20
Q

serves as a neurotransmitter, smooth muscle relaxant, and vasodilator

A

Nitric oxide

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21
Q

function in cell proliferation and growth

A

polyamines spermidine and spermine

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22
Q

Following hydroxylation of tryptophan to 5hydroxytryptophan by

A

liver tyrosine hydroxylase

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23
Q

a potent vasoconstrictor and stimulator of smooth muscle contraction

A

5-hydroxytryptamine or 5-HT

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24
Q

Kidney tissue, liver tissue, and fecal bacteria all convert tryptophan to ____________, then to indole ____________

A

Trytamine; 3 acetate

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25
Q

Neural cells convert tyrosine to

A

Epineprine

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26
Q

precursor of triiodothyronine and thyroxine

A

Tyrosine

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27
Q

functions in brain tissue as an inhibitory neurotransmitter by altering transmembrane potential differences

A

g-Aminobutyrate (GABA

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28
Q

It is formed by decarboxylation of Lglutamate, a reaction catalyzed by Lglutamate decarboxylase

A

g-Aminobutyrate

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29
Q

an excess of ingested over excreted nitrogen, accompanies growth and pregnancy

A

Positive nitrogen balance

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30
Q

where output exceeds intake, may follow surgery, advanced cancer, and kwashiorkor or marasmus

A

Negative nitrogen balance

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31
Q

ammonia, derived mainly from the

A

aamino nitrogen of amino acids

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32
Q

Subsequent deamination of glutamine in the liver releases ammonia, which is then converted to

A

Non toxic urea

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33
Q

Each day, humans turn over ______ of their total body protein, principally muscle protein

A

1-2%

34
Q

High rates of protein degradation occur in tissues undergoing structural rearrangement such as

A

uterine tissue during pregnancy, tadpole tail tissue during metamorphosis, or skeletal muscle in starvation

35
Q

Of the liberated amino acids, approximately _____are reutilized

A

75%

36
Q

The excess nitrogen forms

A

Urea

37
Q

The susceptibility of a protein to degradation is expressed as its half-life

A

1/2

38
Q

Half-lives of liver proteins range from under

A

30 minutes - 150 hours

39
Q

Typical “housekeeping” enzymes have

A

t1/2 values of over 100 hours

40
Q

By contrast, many key regulatory enzymes have a

A

t1/2 of 0.5–2 hours

41
Q

target some proteins for rapid degradation

A

PEST proline, glutamate, serine and treonine

42
Q

The resulting peptides are then degraded to amino acids by

A

Endopeptidases

43
Q

remove amino acids sequentially from the amino and carboxyl terminals, respectively

A

Aminopeptidases and carboxypeptidases

44
Q

Extracellular, membrane-associated, and long-lived intracellular proteins are degraded in lysosomes by

A

ATP independent process

45
Q

By contrast, degradation of abnormal and other short-lived proteins occurs in the cytosol and requires

A

ATP and ubiquitin

46
Q

protein that targets many intracellular proteins for degradation

A

Ubiquitin

47
Q

Only ___of 76 residues differ between yeast and human ubiquitin

A

3

48
Q

A thioester exchange reaction transfers activated ubiquitin to

A

E2

49
Q

catalyzes transfer of ubiquitin to e -amino groups of lysyl residues of target proteins

A

E3

50
Q

Degradation occurs in a multicatalytic complex of proteases known as the

A

Proteasome

51
Q

responsible for degrading proteins are in the stomach, pancreas, and small intestine

A

Proteolytic enzyme

52
Q

Pancreatic proteases further cleave ___________initially digested by the stomach

A

Polypeptides

53
Q

Enteropeptidase from the intestine activates pancreatic enzymes such as ___________ to its active form

A

Trypsinogen

54
Q

SMALL INTESTINE •Contains ____________that cleaves oligopeptides to produce free amino acids

A

Aminopeptidase

55
Q

further hydrolyzed in the cytosol before being released to the portal system

A

Dipeptides

56
Q

ammonotelic

A

Excrete ammnonia fish

57
Q

which must conserve water and maintain low weight, are uricotelic and excrete uric acid as semisolid guano

A

Birds

58
Q

Many land animals, including humans, are ________ and excrete nontoxic, water-soluble urea

A

Ureotelic

59
Q

Urea biosynthesis occurs in 4 stages

A

transamination (2) oxidative deamination of glutamate (3) ammonia transport (4) reactions of the urea cycle

60
Q

Transamination interconverts pairs of

A

a-amino acids and a-keto acids

61
Q

participate in transamination except

A

lysine, threonine, proline, and hydroxyproline

62
Q

present at the catalytic site of aminotransferases and of many other enzymes that act on amino acids

A

Pyridoxal phosphate

63
Q

During transamination, bound PLP serves as a

A

Carrier of amino acids

64
Q

removal of a-amino nitrogen by transamination, the remaining carbon “skeleton” is

A

Degraded

65
Q

These 2 enzymes catalyze the transfer of amino groups to pyruvate (forming alanine) or to aketoglutarate (forming glutamate

A

Alanine amino transferase ang glutamate amino transferase

66
Q

Since alanine is also a substrate for glutamate aminotransferase, all the amino nitrogen from amino acids that undergo transamination can be concentrated in

A

Glutamate

67
Q

the only amino acid that undergoes oxidative deamination at an appreciable rate in mammalian tissues

A

L glutamate

68
Q

The formation of ammonia from a-amino groups thus occurs mainly via the

A

a -amino nitrogen of L-glutamate

69
Q

Transfer of amino nitrogen to a-ketoglutarate forms

A

L glutamate

70
Q

Release of this nitrogen as ammonia is then catalyzed by hepatic L-glutamate dehydrogenase (GDH), which can use either NAD+ or NADP+

A

L glutamate dehyrogenase GH

71
Q

Conversion of a-amino nitrogen to ammonia by the concerted action of glutamate aminotransferase and GDH is often termed

A

Transdeamination

72
Q

allosterically inhibited by ATP, GTP, and NADH and activated by ADP

A

Liver GDH activity

73
Q

The reaction catalyzed by GDH is freely reversible and functions also in

A

Amino acid synthesis

74
Q

Ammonia may be toxic to the brain in part because it reacts with

A

a-ketoglutarate to form glutamate

75
Q

The urea cycle consists of

A

five reactions - two mitochondrial and three cytosolic

76
Q

the carrier of these carbon and nitrogen atoms

A

Ornithine

77
Q

functions as an enzyme activator

A

N-acetylglutamate

78
Q

This is the rate-limiting enzyme of the urea cycle

A

Carbamoyl Phosphate Synthase I

79
Q

rate-limiting enzyme of the urea cycle •This enzyme is active only in the presence of its allosteric activator

A

N-acetylglutamate

80
Q

Formation of carbamoyl phosphate requires

A

2 mol of atp

81
Q

catalyzes transfer of the carbamoyl group of carbamoyl phosphate to ornithine, forming citrulline and orthophosphate

A

L-Ornithine transcarbamoylase

82
Q

autosomal recessive defect in the gene for arginase

A

Hyperargininemia

BiochemistryCONVERSION OF AMINO ACIDS TO SPECIALIZED PRODUCTS (1 decks)

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