Biochem lec 5A - important questions Flashcards
first phase of amino acid catabolism
-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
what is the first step in catabolism of most AA
transamination - transfer of their a-amino group to a-ketoglutarate
products of transamination
a-keto acid and glutamate
what is the most common N acceptor
a-ketoglutarate
what is transamination catalzyed by
aminotransferase
(transfer of amino group from one carbon skeleton to another)
all aa participate in transamination in their catbaolims except
lysine and threonine (deamination instead)
deamination def
deaminatino results in the libteration of the amino group as free ammonia
what is deamination of glutamate to a-ketoglutarate catalzyed by
glutamate dehydrogenase
what is the major disposal form of amino group derived from amino acids, and accounts for 90% of N components in urine
urea
urea is produced where and tranported how to where for excretion in urine
produced by liver, transported in blood to kidneys
what does the urea cycle convert and why
ammonia to urea (less toxic)
what is the rate limiting step in urea cycle
carbamoyl phosphate synthetase I
what is an essential activator of carbamoyl phosphate synthetase I
N-acetylglutamate
glucogenic AA
whose catabolism yields pyruvate or one of the intermedaites of the TCA cycle
ketogenic AA
whose catbolism yields either acetoacetate or one of its precursors (acetly CoA or acetoacetly CoA)
phenylketonuria (PKU)
-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
albinism reults from what
results from lack of tyrosinase, and thus melanin is not produced
albinos get skin cancer easily
what is the major site of heme biosynthesis
liver and erythrocyte-producing cells of bone marrow (bone marrow accounds for about 85%)
initial reaction and the last 3 steps in the formation of porphyrins occur where, and where do the intermediate steps occur
intermediate steps in the cytosol
last 3 steps in the mitochondria
why are mature rbcs unable to synthesize heme
lack mitochondria
degradation of heme (2 steps)
heme converted to biliverdin and CO by heme oxygenase
biliverdin converted to bilirubin by biliverdin reductase
enzyme for heme to biliverdin
heme oxygenase
enzyme for biliverdin to bilirubin
biliverdin reductase
bilirubin characteristics
very toxic and insoluable
jaundice (iterus)
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)
norepinephrine and epinephrine function
-regulate carbohydrate and lipid metabolism
-involved in fight or flight response
parkinson disease due to what
due to insufficient dopamine production caused by the loss of dopamine-producing cells in the brain (neurodegenerative movement disorder)
catecholamines are inactived by deamination using what as the methly donor
SAM
metabolic products of catecholamine inactivation are excreted in the urine as
vanillylmandelic acid (VMA) from epinephrine and noreepinephrine, and homovanillic acid (HVA) from dopamine
degradtion of epinephrine and norepinephrine becomes what
VMA
degradtion of dopamine becomes what
HVA
histamine involed w what
imflammatory reactions and gastric secretion
histidine becomes what through what enzyme
histidine -> histamine through decarboxylase PLP
tryptophan becomes what
serotonin
what is creatine
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
amount of creatine phosphate in body is proprtional to what
muscle mass
what are the precursors to creatine phosphate
arginine and glycine
melanin is synthesized from what
tyrosine using enzyme tyrosinase
melanin helps w what
protects underlying cells from harmful effects of sunlight
2 families of nucleotides
purines and pyrimidines
pyrimidine
cut the pie
(cytosine, uracil, thymine)
purines
pure as gold
adenine, guanine
nucleoside structure
nitrogenouse base and pentose monosaccharide (no phosphate)
nucleotide
nucleoside + phosphate
ribonucleoside
if the sugar is a ribose
deoxyribonucleoside
if the sugar is deoxyribose
purine ring is constructed where
in the liver
Ribose 5 - phosphate to PRPP through what enzyme
PRPP synthetase
what aa are in PRPP to IMP
glutamine, glycine, aspartate
AMP and GMP are converted to the dexy form by
Ribonucleotide reductase
what enzyme for hypoxanthine to IMP
hypoxanthine-guanine PRPP
what enzyme for guanine to GMP
hypoxanthine-guanine PRPP
what enzmye for adenine to AMP
Adenine PRPP
What is the treatment for GOUT
treatment with allpurinol (inhibits xanthine)/xanthine oxidase
what converts xanthine to uric acid
xanthine oxidase
what inhibits the enzyme that converts IMP to AMP and GMP
purinethol (6-mercaptopurine)
what inhibits ribounucleotide redutase
hydroxyurea
what catalyzes UTP to CTP
CTP synthethase
UMP can be phosphorylated to what
UDP and UTP
UTP is then covereted to what
UTP -> CTP
what aa are used in pyrimidine synthesis
glutamine (first step) and aspartate (second step)
what catalzyed dUMP to dTMP
thymidylate synthase
what reduces dihydrofolate to tetrahydrofolate
dihydrofolate reductase
5-fluorouracil inhibits what
inhibits thymidylate synthase
methotrextate
inhibits dihydrofolate reductase
capecitabine inhibits what
inhibits thymidylate synthase
prodrug of 5FU
degradation of pyrimidine nucleotides
beta-amino acids
CO2
NH3
heme syntehsis
heme inhibits what
alas 1
heme syntehsis low lead inhibits what
alas 2
heme syntehsis
lead inhibits what
ALA dehydratase (delta-aminolevulinic acid dehydratase)
Ferrochelatase (mitchondrial enzyme)
what is precursor of heme
glycine, succinyl CoA
