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Biomed > Biochem lec 5A - important questions > Flashcards

Biochem lec 5A - important questions Flashcards

1
Q

first phase of amino acid catabolism

A

-removal of the alpha-amino group forming ammonia and the corresponding alpa-keto acid (the cabron skeletons of aa)
-a portion of free ammonia is excreted in uring, but most is used in the synthesis of urea, which is quantitavley the most important route for disposing nitrogen from the body

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2
Q

what is the first step in catabolism of most AA

A

transamination - transfer of their a-amino group to a-ketoglutarate

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3
Q

products of transamination

A

a-keto acid and glutamate

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4
Q

what is the most common N acceptor

A

a-ketoglutarate

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5
Q

what is transamination catalzyed by

A

aminotransferase
(transfer of amino group from one carbon skeleton to another)

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6
Q

all aa participate in transamination in their catbaolims except

A

lysine and threonine (deamination instead)

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7
Q

deamination def

A

deaminatino results in the libteration of the amino group as free ammonia

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8
Q

what is deamination of glutamate to a-ketoglutarate catalzyed by

A

glutamate dehydrogenase

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9
Q

what is the major disposal form of amino group derived from amino acids, and accounts for 90% of N components in urine

A

urea

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10
Q

urea is produced where and tranported how to where for excretion in urine

A

produced by liver, transported in blood to kidneys

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11
Q

what does the urea cycle convert and why

A

ammonia to urea (less toxic)

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12
Q

what is the rate limiting step in urea cycle

A

carbamoyl phosphate synthetase I

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13
Q

what is an essential activator of carbamoyl phosphate synthetase I

A

N-acetylglutamate

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14
Q

glucogenic AA

A

whose catabolism yields pyruvate or one of the intermedaites of the TCA cycle

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15
Q

ketogenic AA

A

whose catbolism yields either acetoacetate or one of its precursors (acetly CoA or acetoacetly CoA)

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16
Q

phenylketonuria (PKU)

A

-results in overaccumulation of phenylalanine, due to deficiency of phenylalanine hydroxylase
-strict diet control (to reduce phe) can prevent mental retardation and other brain damage

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17
Q

albinism reults from what

A

results from lack of tyrosinase, and thus melanin is not produced
albinos get skin cancer easily

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18
Q

what is the major site of heme biosynthesis

A

liver and erythrocyte-producing cells of bone marrow (bone marrow accounds for about 85%)

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19
Q

initial reaction and the last 3 steps in the formation of porphyrins occur where, and where do the intermediate steps occur

A

intermediate steps in the cytosol
last 3 steps in the mitochondria

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20
Q

why are mature rbcs unable to synthesize heme

A

lack mitochondria

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21
Q

degradation of heme (2 steps)

A

heme converted to biliverdin and CO by heme oxygenase
biliverdin converted to bilirubin by biliverdin reductase

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22
Q

enzyme for heme to biliverdin

A

heme oxygenase

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23
Q

enzyme for biliverdin to bilirubin

A

biliverdin reductase

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24
Q

bilirubin characteristics

A

very toxic and insoluable

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25
Q

jaundice (iterus)

A

yellow color of skin, nail beds and sclerae (white of eyes) - causes by deposition of bilirubin, secondary to increased bilirubin levels in the blood (hyperbilirubinemia)

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26
Q

norepinephrine and epinephrine function

A

-regulate carbohydrate and lipid metabolism
-involved in fight or flight response

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27
Q

parkinson disease due to what

A

due to insufficient dopamine production caused by the loss of dopamine-producing cells in the brain (neurodegenerative movement disorder)

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28
Q

catecholamines are inactived by deamination using what as the methly donor

A

SAM

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29
Q

metabolic products of catecholamine inactivation are excreted in the urine as

A

vanillylmandelic acid (VMA) from epinephrine and noreepinephrine, and homovanillic acid (HVA) from dopamine

30
Q

degradtion of epinephrine and norepinephrine becomes what

A

VMA

31
Q

degradtion of dopamine becomes what

A

HVA

32
Q

histamine involed w what

A

imflammatory reactions and gastric secretion

33
Q

histidine becomes what through what enzyme

A

histidine -> histamine through decarboxylase PLP

34
Q

tryptophan becomes what

A

serotonin

35
Q

what is creatine

A

high energy compound that provides a small but rapdily mobilized reserve of high energy phosphates that can be reversibly transferred to ADP to maintain the intracellular level of ATP during the few minutes of intese muscular contraction

36
Q

amount of creatine phosphate in body is proprtional to what

A

muscle mass

37
Q

what are the precursors to creatine phosphate

A

arginine and glycine

38
Q

melanin is synthesized from what

A

tyrosine using enzyme tyrosinase

39
Q

melanin helps w what

A

protects underlying cells from harmful effects of sunlight

40
Q

2 families of nucleotides

A

purines and pyrimidines

41
Q

pyrimidine

A

cut the pie
(cytosine, uracil, thymine)

42
Q

purines

A

pure as gold
adenine, guanine

43
Q

nucleoside structure

A

nitrogenouse base and pentose monosaccharide (no phosphate)

44
Q

nucleotide

A

nucleoside + phosphate

45
Q

ribonucleoside

A

if the sugar is a ribose

46
Q

deoxyribonucleoside

A

if the sugar is deoxyribose

47
Q

purine ring is constructed where

A

in the liver

48
Q

Ribose 5 - phosphate to PRPP through what enzyme

A

PRPP synthetase

49
Q

what aa are in PRPP to IMP

A

glutamine, glycine, aspartate

50
Q

AMP and GMP are converted to the dexy form by

A

Ribonucleotide reductase

51
Q

what enzyme for hypoxanthine to IMP

A

hypoxanthine-guanine PRPP

52
Q

what enzyme for guanine to GMP

A

hypoxanthine-guanine PRPP

53
Q

what enzmye for adenine to AMP

A

Adenine PRPP

54
Q

What is the treatment for GOUT

A

treatment with allpurinol (inhibits xanthine)/xanthine oxidase

55
Q

what converts xanthine to uric acid

A

xanthine oxidase

56
Q

what inhibits the enzyme that converts IMP to AMP and GMP

A

purinethol (6-mercaptopurine)

57
Q

what inhibits ribounucleotide redutase

A

hydroxyurea

58
Q

what catalyzes UTP to CTP

A

CTP synthethase

59
Q

UMP can be phosphorylated to what

A

UDP and UTP

60
Q

UTP is then covereted to what

A

UTP -> CTP

61
Q

what aa are used in pyrimidine synthesis

A

glutamine (first step) and aspartate (second step)

62
Q

what catalzyed dUMP to dTMP

A

thymidylate synthase

63
Q

what reduces dihydrofolate to tetrahydrofolate

A

dihydrofolate reductase

64
Q

5-fluorouracil inhibits what

A

inhibits thymidylate synthase

65
Q

methotrextate

A

inhibits dihydrofolate reductase

66
Q

capecitabine inhibits what

A

inhibits thymidylate synthase
prodrug of 5FU

67
Q

degradation of pyrimidine nucleotides

A

beta-amino acids
CO2
NH3

68
Q

heme syntehsis
heme inhibits what

A

alas 1

69
Q

heme syntehsis low lead inhibits what

A

alas 2

70
Q

heme syntehsis
lead inhibits what

A

ALA dehydratase (delta-aminolevulinic acid dehydratase)
Ferrochelatase (mitchondrial enzyme)

71
Q

what is precursor of heme

A

glycine, succinyl CoA

Biomed (18 decks)

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