Biochem Block 4
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Biochem Block 4
Biochem Block 4
What enzyme catalyzes the formation of cAMP?
cAMP pathway uses what type of receptor?
G protein--7 transmembrane domains
When a hormone binds a G protein, GDP is exchanged for what?
What are the 3 subunits of G protein?
Upon binding of a hormone, what subunit dissociates and binds the enzyme?
GTPase activity is present on what subunit?
cAMP activates what kinase?
protein kinase A
Phosphorylation is usually on what a.a residue?
O glycosidic bonds are formed from what a.a?
What effect does Cholera have on the G protein activity?
activation of alpha s subunit which constitutively activates protein kinase A
Cholera uses what receptor?
ADP ribosylation of alpha s subunit of Gprotein is caused by what toxin?
What causes constitutive activatio of alpha s Subunit of G protein?
What inhibits GTPase activity of alpha s subunit?
What is the sourse of ADP ribosylation?
What hormones act thru Gi receptor?
What is the difference between Gs and Gi receptor proteins?
upon activation of Gs--cAMP is activated
Upon activation of Gi--cAMP is deactivated
What hormone stimulates phosphodiestarase?
Methyl Xanthine has what effect on phosphodiesterase?
it inhibits it----possible hyperglycemia
What are the two types of Guanylyl cyclase?
What are the hormones that act thru cGMP?
ANF acts thru what type of cGMP receptor, membrane or cytosolic?
NO acts thru what type of cGMP receptor, membrane or cytosolic?
cGMP stimulates what protein kinase?
protein kinase G
What is the action of Silenafil?
prevents breakdown of
Insulin is needed for entry of glucose into what cells?
Mutation of RAS gene causes what?
decreased hydrolysis of GTP to GDP
G protein is constitutively active
Source of ADP ribosylation?
What two toxins do ADP ribosylation?
Cholera and E.coli cause what by constitutively activating alpha s subunit?
diarhea bc of increased Cl secretion which takes water out
What effect does Pertussis toxin have?
Mode of action of pertussis toxin?
ADP ribosylation of Gi receptor protein
Insulin is made up of how many a.a?
Insulin has what kind of chains?
intra chain disulfide bonds
inter chain disulfide bonds
Initially insulin is synthesized as what?
Where is the one polypeptide proinsulin is cut into two peptides?
Glucagon is made up of how many a.a?
Glucagon acts on what organ?
Glucagon stimulates glycogen metabolism in what organ?
What happens to acetone that is produced?
it is exhaled
What are the 2 organs that undergo gluconeogenesis?
How does the kidney compensate for the ketoacidosis?
it uses ammonia to neutralize H+
What kind of obesity has worse health consequence
What is the mode of action of Orlistat?
Inhibits pancreatic lipases and gastric lipases
How does sibutramine work?
Serotonin or norepinephrine reuptake inhibitor
"Metabolic Syndrome" is associated with what?
Why do men loose fat more easily because?
Has access to portal circulation
Lipoprotein lipase digests TAG found where?
Class III obesity is what BMI?
Class II obesity is what BMI?
Class I obesity is what BMI?
Numbering of purine rings is done in what direction?
Numbering of carbon and nitrogen atoms in a pyrimidine is in what direction?
What is the difference between ribose and deoxyribose?
ribose--OH on 2'
deoxyribose--H on 2'
Methylation of uracil produces what?
What is the rate determining step of De novo purine synthesis?
Glutamine PRPP amidotransferase
Sulfonamides like Trimethropin inhibits what enzyme?
Methotrexate inhibits what enzyme?
What is the only enzyme that uses thiamine only?
6-Mercaptopurine is an inhibitor of what 2 enzymes?
6-Mercaptopurine blocks synthesis of what 2 nucleotides?
Why is GTP used in the synthesis of AMP and ATP used in the synthesis of GMP?
To balance the use of nucleotides
Lesch-Nyhan syndrome is caused by a deficiency of what enzyme?
What enzyme is involved in the making of uric acid?
What amino acidpathy mimics the symptoms of Uric acid?
Gout is caused by deposition of what?
Inhibitor of xanthine oxidase
What is a competitive inhibitor of Aspartate transcarbamoylase?
5 Fluorouracil does what?
inhibits thymidylate synthesis
Trimethropin does what?
inhibits bacterial dihydrofolate reductase
Methotrexate does what?
inhibits bacterial dihydrofolate reductase
Ribonucleotide reductase is inhibited by what?
What enzyme is used to reduce the 4 ribonucleotides?
What reducing agent is used to reduce ribonucleotides?
What is used along with ribonucleotide reductase to reduce ribonucleotide
What is the result of dATP binding to ribonucleotide reductase activity site?
decreased catalytic activity
prevents DNA synthesis
Adenosine deaminase deficiency primarily affects what kinds of cells?
High levels of dATP have what effect?
decreased ribonucleotide reductase activity
What chemical prolongs the half life of adenosine deaminase?
PEG --polyethylene glycol
What are the enzymes that require vit b 1?
alpha keto acid dehydrogenase
branched chain AA dehydrogenase
Beri Beri results from a deficiency of what?
Vit b 1
BeriBeri results in what?
In alcoholics with vit b1 deficiency you get what?
Vit B1 and 2 are found where?
Deficiency of Vit b2?
What does Folate carry/Transfer?
What is checked at end of G1 phase?
Is the pentose sugar or the nitrogenous base labeled with the " prime" symbol?
What kind of bond connects the phosphate in a nucleotide?
What are the precursors of purine?
glycine, CO2, N-10 tetrahydrofolate, glutamine, aspartate
What is the rate limiting step in de novo purine synthesis?
glutamine PRPP amidotransferase
What activates Glutamine PRPP amidotransferase?
What inhibits Glutamine PRPP amidotransferase
Sulfanamides inhibit what?
synthesis of Folate
What is the mode of action of Sulfanamides?
blocks Dihydropteroate synthase
Trimethropin inbihits what?
Methotrexate inhibits what?
Human dihydrofolate reductase
Conversion of IMP to AMP requires what type of high energy molecule?
Conversion of IMP to GMP requires what type of high energy molecule?
Mycophenolic acid blocks what enzyme?
What drug is used in preventing graft rejection?
Degradation of nucleic acids produces what?
Hypoxanthine-guanine phosphoribosyltransferase uses what two precursorse to produce IMP and GMP?
Hypoxanthine + PRPP--->IMP
Guanine + PRPP----> GMP
How are dietary sources of vitamin A absorbed?
esters are broken down into retinol
retinol is absorbed
retinol is esterified into esters
Lipid soluble vitamins are carried how from the intestinal cell?
in the chylomicron
Too much retinoic acid causes what?
Are teratogens mutagens?
Examination of what PTH derivative establishes its presence?
How does calcium exist in plasma?
50 % free (ionized)
50% protein bound
How does a malignant myeloma cause hypercalcemia?
What are the 2 signs of Hypocalcemia?
Hypocalcemia in kids?
Hypocalcemia in adults?
What is the abreviation of dicarboxylic glutamate?
What is the rate determining step in purine synthesis?
What inhibits xanthine oxidase?
What prevents reabsorption of uric acid in the PCT?
Glutamine-PRPP amidotransferase is inhibited by?
IMP, GMP, AMP
IMP dehydrogenase is inhibited by?
Adenylosuccinate is inhibited by?
What deoxyribonucleotide inhibits Ribonucleotide reductase?
What stimulates the activity of Ribonucleotide Reductase?
Hydroxyurea blocks what enzyme?
Severe combined Immunodeficiency diseases is caused by a deficiency of what enzyme?
What accumulates in Adenosine Deaminase deficiency?
dATP from adenosine
fyi..adenosine + PRPP-->AMP-->ADP-->dADP--dATP
What is the consequence of accumulated dATP on Nucleotide synthesis?
dATP inhibits Ribonucleotide Reductase--> no nt
no nt--> low division of cell especially..lymphocytes
What extends the life of AD?
What is the rate limiting enzyme pyrimidine synthesis?
carbamoyl phosphate synthase II
What two sources give rise to a pyrimidine ?
What enzyme converts dUMP to dTMP?
What drug binds to thymidylate synthase and thus preventing the conversion of dUMP to dTMP?
5 Fluoro Uracil (5FU)
What is the methyl donor in the conversion of dUMP to dTMP?
N5N10 methylene tetrahydrofolate
CTP synthase is inhibited by what?
activated by what?
What drugs allows for suicide inhibition?
Methotrexate and Trimethropin are what type of inhibitors?
What are the degradation products of Pyrimidines?
Thymine--->methylmalonyl coA-->succinyl coA
Receptors for steroid hormones, thyroid and retinoic acid have what 2 domains on the intracellular receptors?
ligand binding domain for the hormone
DNA binding domain
Gs protein is also called what?
Which subunit of a Gs protein has GTPase activity?
What subunit of the G protein detaches with the GTP and binds to AC?
Phosphorylation takes place on what a.a residue?
serine or threonine
What toxin causes ribosylation of the alpha subunit?
What hormones act thru the Gi proten?
What calcium binding protein is used intracellularly?
Receptor for what hormone has intrinsic kinase activity?
How does mutated ras gene cause uncontrolled proliferation?
alpha s subunit is constitutively active
What 2 toxins cause ribosylation of alpha s subunit?
By what mechanism is the cholera brought on?
E.coli----no degradatation of GTP to GDP
phosphorylation of CFTR channel--loss of Cl
Proinsulin to insulin cleavage occurs where?
in the Golgi Apparatus
Which 2 G.I hormones stimulate the release of Insulin?
Gastric Inhibitory Protein
What is the mechanism of insulin secretion after glucose uptake?
glucose metabolized--> high ATP
High ATP---> prevents efflux of K+
high Intracellular K+---> depolarization
Ca influx---> fusion of vesicle with PM
What effect does insulin have on HMP shunt?
it promotes it b/c in fed state you can allow urself to maintain upkeep..which HMP shunt does by producing NADPH and Ribulose-5-phosphate
What is the a.a chain length of insulin?
Branched chain a.a are primarily metabolized where?
What are two symptoms of Hypoglycemia?
Adrenergic---due to epi
Neuroglycopenia---low glucose in brain
What are the 2 regulatory systems that respond to hypoglycemia?
alpha cells of islets of langerhans--glucagon
What BMI is overweight?
Obese class I--- >30
Obese Class II--- >35
Obese Class III --- >40
Men's obesity is classified as what?
Woman's obesity is classified as what?
What type of obesity, Android or Gynecoid has worse health consequences?
Why do men tend to loose faster?
because the abdominal fat(android) has a
- higher turnover rate
- more hormone sensitive
Leptin is produced by what cells?
What action does leptin have on the hypothalamus?
leptin inhibits hunger center in the brain
Nutritional hormones relay to what part of the brain?
What 2 nuclei in the hypothalamus control fuel intake and metabolism?
What hypothalamic nucleus stimulates eating?
Orexigenic nucleus secretes what peptide to stimulate eating?
Anorexigenic nucleus produces what signal that prevent eating?
Is Leptin appetite stimulating or inhibiting?
leptin is appetite inhibitng
Is ghrelin appetite stimulating stimulating or inhibitng?
Which neurons, orexigenic or anorexigenic are inhibited by leptin?
TNF-alpha has what effect on insulin resistance?
increases insulin resistance
What effect does PYY-36 have on the appetite?
in inhibits it
What 3 hormones inhibit the orexigenic neurons from releasing neuropeptide Y?
What are the 3 components of metabolic syndrome?
How does insulin resistance lead to dyslipidemia?
hormone senstitive lipase is not inhibited by insulin
HSP breaks down TAGs
increases of FA and cholesterol
What does orlistat do?
prevents release of pancreatic and gastric lipase
What does subatramine do?
serotonin and norepinephrine reuptake inhibitor
Prothrombin Time (PT) tests which clotting pathway?
PTT tests which clotting pathway?
What receptor does Insulin and Growth hormone use?
associated tyrosine kinase
What receptor do growth factors like PDGF, Insulin?
Intrinsic tyrosine kinase
What receptor uses JAK/STAT?
associated tyrosine kinase
15-17 translocation produces what condition?
Acute Meylegenous Leukemia
11-22 translocation produces what cancer?
11-14 translocation produces what cancer?
Mantle cell Lymphoma
Koilychia and dysphagia are caused by what?
iron deficiency anemia
What effect do nitrates have on hemoglobin?
nitrates oxidize ferrous iron to ferric
What is responsible for the polymerization of HbS?
hydrophobic interactions between the globin genes because of the valine instead of the glutamate
What is the antidote for cyanide poisoning?
administration of nitrites b/c nitrites oxidize hemoglobin to methemoglobin which binds CN- with high affinity sequestering it from the mitochondria
Radiation has what 2 effects on cells?
introduces double strand breaks
produces free radicals
The most abundant amino acid in collagen?
During exercise what metabolite stimulates the breakdown of glycogen?
Disulfide bond is an example of what type of protein structure?
Where does CO2 bind on a hemoglobin molecule?
amino terminal of
Which hemoglobin form T or R has higher oxygen affinity?
Alport's syndrom is due to what?
abnormal type IV collagen
What are the 3 symptoms of Alport's syndrome?
What is an example of super-secondary structure?
Proteins with super-secondary protein structures usually perform what function?
Proteins with sequences are degraded ubiquitously without selection?
Digestion of what is mostly affected in cystic fibrosis?
Which monosaccharide is not dependent on sodium- monosaccharide synport?
What activates trypsin?
What is the mode of action of orlistat?
blocks gastric and pancreatic lipases
Gamma glutamyl transferase is used for what?
amino acid transport across the cell membrane of the intestinal cell
What traps the glucose in the cell?
phosphorylation via glucokinase
What effect does HPV have on p53?
E6 protein degrades p53