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Which of the following hormones triggers glycogenolysis?
Which of the following compounds serves as an activated monomer of glycogen synthesis?
-Note: glycogen synthesis utilizes activated glucose monomer UDP-glucose, to extend the polymer by one unit
Glycogen phosphorylase using inorganic phosphates (Pi) breaks the main chain of glycogen to produce
Which of the following compound is an immediate product of glycogen phosphorylase?
-Glucose 1 phosphate
note: Glycogen also
A liver biopsy of an infant revealed the glycogen structure. Which of the following is deficient in
If the glucosidase activity of debranching enzyme is defective, during glycogenolysis the
Will contain a single residue at the branch point
The glucose 1-phosphate produced by the action of phosphorylase is converted into glucose 6- phosphate by the enzyme
In the following reaction below, GTP⇒cGMP +PPi⇒2Pi formation of cGMP is catalyzed by
A glycogen polysaccharide contains 241 residues and no branches. Assuming complete
glycogenoysis of the above polysaccharide how many moles of (net) ATP are produced through glycolysis?
Which of the following compounds convert phosporylase b tense form (T) into a more relaxed (R) form?
Phosphorylase Kinase-P (active)
Which enzyme is activated to form the second messenger cAMP when glucagon binds to liver
cell surface receptors?
PLC cleaves phosphatidyl-inositol bisphosphate into DAG and
Phosphorylation of glycogen synthase reduces its affinity toward its substrate
When α-adrenergic receptors are stimulated there is an increase in the activity of PLC with a resultant increase in PIP2 hydrolysis. The products of PIP2 hydrolysis are...
Von Gierke’s Disease Lack of...
A patient was hypoglycemic especially few hours after the meal. His insulin and glucagon levels were normal. Which of the following enzyme would most likely be deficient in this patient?
Alcoholics may have fatty liver. Which of the following can best explain the mechanism behind this?
In addition to acetyl CoA, fatty acid biosynthesis also requires a reductant
Deficiency of vitamin B12 (deoxyadenosyl cobalamin) would cause which of the following diseases?
Methymalonic aciduria (acidemia)
Phytanic acid is not a substrate for beta-oxidation since it is substituted with:
-Methyl group @ β position.
The first enzyme in α-oxidation pathway is a
Deficient in Refsum’s disease
Which compound can undergo omega oxidation?
-ω-oxidation: more significant for fatty acids with 6 to 10 carbons
All enzymes that use biotin⇒carboxylase
Acetyl CoA carboxylase
Propionyl CoA carboxylase
Β-methyl crotonyl CoA carboxylase
Which of the following compounds is derived from histidine and mediates allergic and inflammatory reactions?
Which of the following compounds can detoxify xenobiotics in liver upon conjugation?
Which of the following cell types makes myelin?
Which of the following amino acid is not utilized in protein synthesis?
Which compounds is produced upon degradation of a ketogenic amino acid?
Most tissues cannot perform the urea cycle. These tissue release_______, which can be
converted into urea by the liver
Conversion of glutamine into glutamate and ammonia is catalyzed by
The following compounds is utilized in carbamoyl phosphate synthesis
___ is converted into urea in liver
The allosteric activator of carbamoyl phosphate synthase I is
Which of the following enzyme is involved in catabolism (inactivation) of catecholamine?
-Catecholamine O-methyltransferase (COMT)
-Monoamine oxidase (MAO)
act sequentially to inactivate catecholamines.
SAM mediated methylation
Catecholamine (epinephrine) synthesis
Phosphatidyl choline synthesis
Tryptophan derived compounds
What chemical messenger is formed from histidine, and its reaction is catalyzed by histidine decarboxylase found in mast cell?
i. Histidine⇒histidine decarboxylase⇒histamine
What mediates allergic and inflammatory reactions?
A coenzyme (vitamin derivative)that serves as a one carbon, donor for purine synthesis is
During the biosynthesis of pyrimidines, the two compounds that form the entire pyrimidine skeleton are
PRPP amidotransferase (phosphoriboxylamine transferase, PRAT) catalyzes the formation of
Which of the following enzymes is deficient in hereditary orotic aciduria?
AZT potently inhibits
RNA dependent DNA polymerase (reverse transcriptase)
Which of the following compounds is a committed metabolite for the denovo biosynthesis of purine?
PRPP combines with an amino group from glutamine to form 5’phosphribosylamine and PPi ,
catalzyed by the enzyme
PRPP amidotransferase/phosphoribosylamine transferase (PRAT)
Which of the following compounds is a common precursor for the biosynthesis of AMP and GMP?
A rate limiting step in nucleotide biosynthesis is catalyzed by
Carbamoyl phosphate synthase II
A compound that is utilized for de novo synthesis of purine, pyrimidine, salvage pathway, and NAD+ is
Compound that is an allosteric aactivator of PRPP amidotransferase?
Xanthine Oxidase catalyzes the formation of
__________ cannot perform de novo synthesis and are solely dependent upon salvage pathway
During the catabolism of purines, guanosine is converted into guanine and ribose-1-phosphate using _____, catabolized by the enzyme purine nucleoside phosphorylase (PNP).
Purine nucleoside phosphorylase (PNP), using the substrates guanosine and Pi, forms
The ultimate end product of urine degradation is
The enzyme that is deficient in gout and Lesch-Nyhan syndrome is...
Hypoxanthine guanine phosphoribosyl transferase
Hyperuricemia is common both in gout and Lesch-Nyhan Syndrome. Which of the following
explanations would be correct in describing hyperuricemia condition?
Higher levels of PRPP induce the de novo synthesis of purines, which eventually are
catabolized to a product that causes hyperuicemia.
GOUT and Lesch Nyhan: ↓HGPRT & ↑PRPP
Purine nucleoside phosphorylase (PNP) deficiency causes
Combined immune deficiency
During cell cycle, DNA synthesis occurs in the following phase
Deoxy UMP (dUMP) is converted into 5-methyl dUMP (dTMP) catalyzed by the enzyme
thymidylate synthase. In this reaction, which of the following compound/coenzyme is used?
*Which of the following compounds serves as a coenzyme for the reaction catalyzed by thymidylate synthase?
N5-N10-methylene THF (vitamin B9 derivative)
Dihydrofolate reductase activity is inhibited by
Which of the following compounds contain the vitamin B5 derivative pantothenate as part of the whole moiety?
*NDP is converted into dNDP by the enzyme
NDP is converted into dNDP catalyzed by the enzyme ribonucleotide reductase, using the coenzyme
Conversion of NDP into dNDP by ribonucleotide reductase involves reduction at position
number ____ of ribose
An amino acid that is required for purine synthesis is
Zinc fingers are part of the
DNA binding domain of the steroid receptor proteins
Conversion of cholesterol into pregnenolone and isocaptroaldehyde occurs inside the
*What is the role of (steroidogenic acute regulatory) StAR protein?
*Which of the following enzymes is deficient in congenital adrenal hyperplasia?
Steroid 21-hydroxylase (CYP21A2)
*During menstruation, apoptosis (programmed cell death) is induced due to the withdrawal of
A plasma protein that binds nonspecifically to steroids is_____
cholesterol serves as a precursor for
The ______ receptor protein is normally associated with heat shock protein (90kD)
Receptors for cortisol and aldosterone are usually bound to heat shock protein
StAR transport protein that transports cholesterol from cytosol into mitochondrial matrix where cholesterol can be cleaved into pregnenolone and
Cholesterol is a major precursor that undergoes side chain cleavage (RLS) in the mitochondria to form pregnenolone and C-6 isocaproaldehyde catalyzed by side chain cleavage enzyme called
The conversion of testosterone into estradiol is catalyzed by steroid
Cortisol synthesis and secretion is stimulated by
Testosterone is converted into a more potent androgen dihydrotestosterone (DHT) in some
androgen target cells before binding to the androgen receptor. This conversion requires the activity of
5 α-reductase that is located in the ER
Cholesterol is converted into pregnenolone inside themitochondrial matrix catalyzed by the
enzyme desmolase (20-22 lyase). For this reaction the cytosolic cholesterol is made available into the mitochondrial matrix by a transport protein called
Steroidogenic acute regulatory protein (StAR)
The most potent androgen is
Guanylate cyclase catalyzes the formation of the second messenger
The conversion of cholesterol into pregnenolone is catalyzed by
Desmolase/cholesterol 20-22 lyase
The conversion of testosterone into dihydrotestosterone (DHT) is catalyzed by steroid
In CAH, steroid 21-hydroxylase is deficient. Reason behind salt imbalance
Addison’s disease is an overall deficiency of adrenal steroid hormones. Patients are
hypoglycemic due to decreased levels of
Prolonged exposure to glucocorticoids, either due to the use of cortisol as an anti-inflammatory
drug or due to tumors of adrenal cortex results in
Which of the following compounds inhibits angiotensin converting enzyme (ACE)?
Along with estradiol, which of the following hormones cause endometrial wall thickening?
___________is a catabolic product of estradiol and a potent breast cancer inducer.
16-hydroxy estrogen (16-OHEN)
Which of the following enzymes is deficient in testicular feminization?
Steroid 5 α-reductase
Steroid hormones are inactivated upon conjugation with
Estradiol is inactivated upon conjugation with
Normally in vivo, steroid hormones are inactivated upon conjugation to
Receptor proteins for testosterone, estradiol and progesterone are located in the
With reference to steroid hormone induced gene expression, which of the following statement
best explains zinc fingers?
They contain zinc ions, and are part of the steroid hormone receptor that facilitates its
binding to DNA
Zinc fingers commonly refer to
The parts of the steroid hormone receptor proteins that are coordinated to zinc and
bind to DNA
In Wernicke-Korsakoff syndrome the conversion of pyruvate to acetyl CoA is deficient. Which vitamin metabolism is affected?
The contraction of the gallbladder to secrete bile is stimulated by
CCK (cholecystokinin) causes the secretion of
The release of enzymes and the secretion of the juice rich in bicarbonate from pancreas are
Guanylin causes the secretion of
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