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Single Response: (1st group)


Deficiency of which of the following vitamins can lead to anemia?




folic acid




vitamin B12




vitamin C




vitamin E




all of the above




Which line in the following table best represents the U. S. Government recommended distribution of Calories among dietary fat, carbohydrate and protein?

                Fat(%)    Carbohydrate(%)   Protein(%)




       10                      80                      10




       30                      60                     10




       40                       20                     40




        60                      20                     20




        80                      10                     10




All of the following are true of the basal energy expenditure (BEE), also known as the basal metabolic rate (BMR) EXCEPT




the decrease in old age due to loss of muscle mass is inevitable




it is generally higher for men than for women of equal age and surface area




measurements are made in the fasted state




decrease in old age can lead to so great a decrease in caloric need that deficiency of essential nutrients can result.




it peaks in the first years of life




Substances with vitamin D activity




may be obtained only from animal sources or exposure to sunlight




may be obtained only from plant sources or exposure to sunlight




may be obtained from plant or animal origins.




are absorbed from the intestine less effectively as an individual ages




are synthesized in the skin with undiminished ability as an individual ages




In the absorption of dietary calcium




vitamin D status is equally important in calcium-rich and calcium-poor diets




some kinds of dietary fiber appear to enhance calcium absorption




animal protein has a negative effect




fish with soft bones (e.g., canned salmon) are poor sources of calcium




soluble calcium salts are the only effective forms of dietary calcium supplementation.




All of the following may have a physiological antioxidant role EXCEPT












vitamin C








vitamin E




Vitamin C is generally associated with acting as a cofactor in which of the following kinds of reaction?
















one-carbon transfer








Vitamin C




inhibits absorption of nonheme iron




antagonizes the action of vitamin E




in large doses cures the common cold




can be made from the amino acid, hydroxyproline, but in amounts insufficient to meet the body's needs.




requirement is increased by cigarette smoking


 Single Response: (2nd  group)


During fasting, all of the following would tend to increase the flux through gluconeogenesis EXCEPT:




The concentration of free amino acids increases




The concentration of glycerol increases




The concentration of cyclic-AMP rises




The concentration of fructose-2,6-bisphosphate rises




The enzyme phosphoenolpyruvate carboxykinase is induced




All of the following contribute to the increase in ketone body synthesis in the liver during fasting EXCEPT:




The increased insulin to glucagon ratio activates lipoprotein lipase in adipose tissue




Increased blood concentrations of free fatty acids bound to albumin




Inactive acetyl CoA carboxylase




More flux through beta-oxidation




The liver makes more acetyl CoA than the TCA cycle can use




A patient with type I diabetes has come to the emergency room with ketoacidosis. All of the following might help to explain why her ketones are high EXCEPT:




Protein kinase A in her liver is to high




Free fatty acids in her blood are two high




Too much acetyl-CoA is produced by the liver




Too much hydroxymethylglutaryl CoA is produced




Carnitine deficiency




The pKa for ammonium ion is about 9.4 and the pH of blood is about 7.4. The ratio of ammonia to ammonium ion (ammonia/ammonium ion) in blood is about:
























Which of the following enzyme reactions takes place during the synthesis of urea from ammonium ion and glutamate?




Carbamoyl phosphate + citrulline = ornithine




Aspartate + citrulline + ATP = argininosuccinate + AMP + PPi




Argininosuccinate = aspartate + arginine




CO2 + NH4+ + 2 ADP = carbamoyl phosphate + 2 ATP




Argininosuccinate = arginine + urea




All of the following would be expected to increase the activity of the urea cycle EXCEPT








Switching to a high protein diet




Going from the fed state of a normal diet to a fasting state




An increase in gluconeogenesis








Which of the following is an essential amino acid?
























The products of the catabolism of cysteine are:




Serine and phosphate




Serine and HCl




Pyruvate and sulfate




Serine and sulfate




Alanine and sulfate




All of the following are substrates or products of the phenylalanine hydroxylase reaction EXCEPT:
























You suspect that your 12 year old male patient has an inborn error in methionine metabolism. It may be that cystathionine synthase is deficient. If this is true, he should have high serum concentrations of:




















Methyl cobalamin




1-  Plants and most of animals have the ability to synthesize vitamin C from D-glucose via uronic acid pathway.

[   T   ]

2-  D-ascorbic acid is the physiologically active form of vitamin C

[   F   ]

3-  Ascorbic acid is reversibly reduced to form dehydroascorbic acid.               

[   F   ]

4-  Citrus fruits and green vegetables are good sources of ascorbic acid.            

[   T   ]

5-  Ascorbic acid is a fat soluble antioxidant.                                  

[   F   ]

6-  Vitamin C deficiency leads to scurvy.          

[   T   ]

7-  The dye used in ascorbic acid determination is dichloro-phenolindophenol.

[   T   ]

8-  Ascorbic acid content of food is not affected by storage

[   F   ]

9-  Ascorbic acid is a strong reducing agent.     

[   T   ]

10-  Vitamin C decreases the absorption of iron from the intestine.

[   F   ]

11. Globulins are soluble in distilled water.


12. Biuret reaction can be given by all proteins.

[   T   ]

13. Albumin can be precipitated by half saturation of ammonium sulfate solution.

[   F   ]

14. Albumin and globulins are heat coagulable proteins.

[   T   ]

15. During precipitation of proteins by Na tungestate, the proteins combine with acid radical to form insoluble salt.

[   T   ]

16. Denatured protein is less soluble than native protein.

[   T   ]

17. Proline & hydroxyproline react with ninhydrin with the production of blue color.

[   F   ]

18. Gliadin and histones are soluble in water.    

[   F   ]

19. Flocculation of proteins takes place when they are heated far away from its pI.       

[   F   ]

20. The solubility of proteins is markedly influenced by pH

[   T   ]


 Stem Questions: (Key Answer down)

 For every question, there are five statements that may be correct or incorrect, choose the Correct  statement (s):

 Group (A):


During the process of glucose production and metabolism,



A) the liver is the main organ of production.

B) metabolism in the glycolytic pathway starts with glucose-6-phosphate.

C) there is a net production of 4 molecules of ATP, by aerobic glycolysis.

D) the liver is the site of gluco-regulatory action of glucagon.

E) human growth hormone stimulates glucose uptake in fat and muscle.




The tricarboxylic acid cycle (kreb's cycle)



A) is a source of adenosine triphosphate(ATP).

B) has a purely catabolic function.

C) converts metabolic energy into chemical energy.

D) allows for the complete combustion of fatty acids.

E) requires co-enzymes for its continued operation.




Glucose transfer across the placenta is:



A) energy dependent.

B) much slower at high concentrations (more than 22 mmol/l).

C) more rapid than fructose transfer.

D) not dependent on a concentration gradient.

E) glucagon dependent.




The following statements relate to the citric acid cycle.



A) acetyl-CoA and oxaloacetate react to form citrate.

B) the cycle reforms oxaloacetate.

C) CO2 evolved in one turn of the cycle originates from the 2 C-atoms of

      the acetyl group in acetyl-CoA used to form citrate. 

D) it is involved in gluconeogenesis from glutamate.

E) it is the main source of NADPH for fatty acid synthesis.



Which of the following might apply to a patient with an inadequately controlled insulin–dependent diabetes?


A) an abnormally slow drop in blood glucose concentration following

     a meal.

B) an abnormally low concentration of fatty acids in the blood.

C) a high concentration of ketones in the blood.

D) glycosuria.

E) an abnormally high rate of glycogen synthesis.




Which of the following hormones stimulate gluconeogenesis?



A) aldosterone.

B) glucagon.

C) insulin.

D) epinephrine.

E) cortisol.




Glycogen synthetase, the enzyme involved in the biosynthesis of glycogen, may



A) be activated by the phosphorylation of a specific serine residue.

B) be activated by increased calcium level.

C) be more specifically defined as UDP-glucose-glycogen glucosyl


D) synthesize glycogen without a polymer primer.

E) employ UDP-glucose as a glucosyl donor.




Which of the following might apply to an infant with glycogen storage disease type 1 (Von Gierke’s disease)?



A) blood glucose is abnormally low after a 6-hour fast.

B) extensive deposition of glycogen occurs in the liver.

C) liver glucose-6-phosphase activity is abnormally high.

D) blood lactic acid levels are high.

E) hypolipemia occurs.




Consider the process involved in the oxidation of H atoms(combined in metabolites) to give water.



A) proteins with conjugated heme groups , called cytochromes, are


B) the rate of electron transport is increased when the ATP/ADP ratio is high.

C) oxidation of the 2 H atoms from the conversion of succinate to

     fumarate can produce, as a consequence, 2 ATP molecules.

D) if phosphorylation is uncoupled, electron transport can never occur.

E) oxidative phosphorylation occurs in the cytosol.




Concerning the urea cycle,



A) the enzyme ornithine transcarbamylase is concerned with the formation      of citrulline from ornithine.

B) all the enzymes are present in the mitochondria.

C) urea is formed from ammonia, CO2 and the amino group of glutamate.

D) 3 high energy-phosphates are consumed in the synthesis of each

      molecule of urea.

E) it takes place in the liver and kidney.




The following statements apply to the biochemical disorder associated with the syndrome called argininosuccinic aciduria.



A) there is a lack of the enzyme carbamylphosphate synthetase.

B) argininosuccinate accumulates in the blood and urine.

C) there is a lack of argininosuccinase activity.

D) a normal amount of urea is produced.

E) there is a lack of the enzyme arginase.




Concerning creatinine



A) the daily urinary output of creatinine for any particular normal adult is

     approximately constant.

B) the weight excreted per day depends mainly on the body’s muscle mass

C) it is the metabolic precursor of muscle creatine.

D) the molecule acquires its methyl group from the amino acid methionine

E) it is formed by the decarboxylation of histidine.




Mammalian biosynthesis of the following require one or more methyl groups to be provided by transfer from methionine through the intermediate S-adenosyl-methionine



A) valine.

B) uridine monophosphate.

C) choline.

D) adrenaline.

E) ribosomal RNA.




Pyridoxal phosphate is required as a cofactor in the following reactions of particular amino acids:



A) deamination.

B) decarboxylation.

C) transamination.

D) desulphuration.

E) acetylation.




Regarding  phenylketonuria



A) it can only be diagnosed after the first year of life.

B) the enzyme phenylalanine hydroxylase is defective.

C) tyrosine builds up in the blood.

D) high levels of phenylpyruvic acid are excreted in the urine.

E) blood from phenylketonurics contains high levels of phenylalanine.



In animals, the following compounds are mainly formed by biosynthesis from tyrosine.


A) serotonin.

B) thyroxine.

C) phenylalanine.

D) adrenaline.

E) homogentisic acid.



Consider the substance L-3,4-dihydroxyphenylalanine (dopa):


A) it can be formed from L-tyrosine.

B) It is a major precursor of tyrosine in the body.

C) L-3,4-dihydroxyphenylethylamine (dopamine) is formed by

     decarboxylation of dopa.

D) dopa is an important neurotransmitter.

E) dopa is an intermediate compound in the biosynthesis of adrenaline.



Which clinical observation(s) below is/are suggestive of Hartnup disease?


A) burnt sugar smell in urine.

B) elevated plasma tyrosine and methionine levels.

C) pellagra-like skin rash.

D) urine darkens upon standing.

E) high fecal levels of tryptophan and indole derivatives.



  Group (B):


A low level of potassium in the plasma may be caused by


A) dehydration.

B) thiazide diuretics.

C) acidosis.

D) primary hyperaldosteronism.

E) a beta-cell tumour of the pancreas.



Hypokalemia may lead to


A) paralytic ileus.

B) mental confusion.

C) increased sensitivity of the renal tubules to antidiuretic hormone(ADH).

D) aciduria.

E) elevation of the ST segment on the electrocardiogram.



Folic acid


A) deficiency leads to megaloblastic anemia.

B) is water soluble.

C) does not require gastric intrinsic factor for its absorption.

D) is found only in animal foods.

E) is necessary for nucleic acid synthesis.



Vitamin K


A) is required for the synthesis of prothrombin.

B) is water soluble.

C) deficiency may contribute to hemorrhagic disease of the newborn.

D) deficiency may result from the use of broad spectrum antibiotics.

E) may be deficient in the diet of certain food fadists.



Vitamin B12


A) requires intrinsic factor for absorption.

B) is water soluble.

C) deficiency can be treated by oral supplementation.

D) is only obtained from animal sources in the diet.

E) is destroyed by cooking.



Concerning iron metabolism:


A) plasma iron is carried by transferrin which is a b-globulin.

B) on an average diet containing 10-15mg of iron, only about 5-15% of the

      iron is absorbed.

C) the total body iron is about 40g.

D) on the average, about 70% of the TIBC is saturated.

E) plasma ferritin determination ia a very good index of iron storage.



The adult human hemoglobin A


A) has a molecular weight of 20.000.

B) has a globin portion containing predominantly alpha and gamma chains.

C) has a higher affinity for oxygen than fetal hemoglobin(Hb F).

D) is produced at a rate of 6 g per day in normal conditions.

E) contains heme groups which are porphyrin- iron structures.



Calcium absorption is


A) increased in diets containing high protein.

B) decreased in celiac disease.

C) increased in high phosphate diets.

D) directly increased by parathormone.

E) decreased in chronic pancreatitis.



Vitamin C:


A) is required for the maturation of collagen.

B) is an antioxidant.

C) is required for steroid hydroxylation.

D) is not synthesized by man and the guinea pig.

E) is needed for the conversion of cholesterol to bile acids.


Which of the following statements regarding vitamin A is true?


A) it is related to tocopherol.

B) it is a component of rhodopsin.

C) its deficiency leads to night blindness.

D) it is also known as opsin.

E) b-carotene is a precursor of vitamin A.



Severe deficiency of vitamin D causes:


A) beri beri.

B) osteomalacia.

C) osteopetrosis.

D) rickets.

E) osteogenesis imperfecta.



The factors helping iron absorption from the intestine are:


A) gastric Hcl.

B) ascorbic acid.

C) oxalates.

D) ceruloplasmin.

E) increased body needs.



Pantothenic acid is a constituent of:




C) coenzyme A.


E) acyl carrier protein (ACP) of fatty acid synthetase.



Factors that shift the oxygen –dissociation curve to the right are:


A) high pH.

B) high pCO2.

C) high 2,3-bisphosphoglycerate.

D) hypothermia.

E) fetal hemoglobin.



Which of the following statements correctly describe transport of O2 by hemoglobin?


A) O2 binds to hemoglobin more avidly than does CO.

B) the binding of O2 to hemoglobin causes a valence change in the iron of

     the heme moiety.

C) each of the four heme moietics binds O2 independently.

D) the plot of percentage of O2 bound versus O2 pressure is sigmoidal in


E) binding of CO to hemoglobin, increases the affinity between

     hemoglobin and O2.



Regarding trace elements:


A) the superoxide dismutase contains zinc.

B) chromium increases the effects of insulin are decreases insulin


C) copper is needed for the activation of glutathione peroxidase.

D) patients with cholestatic liver disease have demonstrated manganese

     deposition in brain tissue.

E) manganese activates xanthine oxidase enzyme.



Concerning Wilson’s disease:


A) it is a genetically determined defect in ATPase.

B) copper is transported normally from the intestine into the liver.

C) copper cannot be transported out of the liver into the bile.

D) it is associated with low serum ceruloplasmin concentration.

E) it is treated by ammonium tetramolybedate.



The following conditions may lead to hypercalcemia:


A) primary hyperparathyroidism.

B) hypoalbuminemia.

C) secondary hyperparathyroidism.

D) pseudohypoparathyroidism.

E) malignant disease.



Key answer:

                                          Group (A):                                        Group (B):

 B      D        E


A      B        D     


A      B        D      


A      D       E


A      B        C         E


B      C       


A      C        D      


A      B       D      


A      B        D      


A      C       D      


A      B        E      


B       E


D      E


 C       E


A      B        E


A      B       D     


A      B        C       D        E


A      C      


B      C        E




B        D      


  B      C      D    


A       B        D        E


A      B       D      


C       E


C      D      E


B        C


A      B      C      D      


D        E


B      D       E     


A      B        D       


B      D      E


A      B        C       D        E


A     C       E    


A      E


 C      E








MedBiochem Exam 3   

For each of the following questions, choose the one best answer  (Answer Key is down).

 1. A DNA deletion occurs 1000 bp upstream of the src protooncogene, causing it to be activated. The sequence deleted is probably a(n):

 A. promoter.

 B. operator.

 C. enhancer.

 D. silencer.

 E. initiator.


2. Your molecular biologist colleague tells you she is "about to run a Western blot." Most likely her first step will be to:

 A. Prepare an acrylamide gel containing urea.

 B. Prepare a hybridization probe.

 C. Prepare an agarose gel.

 D. Prepare an SDS-polyacrylamide gel.

 E. A or C.


3. Which of the following is NOT a possible consequence of a single nucleotide deletion in the coding region of an exon?

 A. Change in reading frame.

 B. Diminution of polyadenylation.

 C. Deletion of the 5' splice site.

 D. Nothing (i. e., no consequence).

 E. Loss of the start codon.


4. Which of the following processes will be affected by naladixic acid in E. coli?

 A. mRNA translation.

 B. mRNA capping.

 C. DNA methylation.

 D. DNA replication.

 E. All of the above.


5. Which of the following is NOT a feature of pseudogenes?

 A. Often lack introns.

 B. Are transcribed, spliced, and polyadenylated normally.

 C. Often have poly(A) tails.

 D. Are not made into mRNA.

 E. A and B.


6. Which of the following would NOT make a good selectable marker for a plasmid expressed in bacteria?

 A. alpha amanatin resistance.

 B. naladixic acid resistance.

 C. tetracycline resistance.

 D. ampicillin resistance.

 E. disruption of the lac Z gene.


7. Which of the following enzymes are NOT used in cDNA cloning?

 A. RNA polymerase.

 B. DNA polymerase.

 C. Reverse transcriptase.

 D. Restriction endonuclease.

 E. DNA ligase.


8. Which statement best describes, "junk" DNA?

 A. Some "junk" DNA may have a function.

 B. It is never transcribed into RNA.

 C. It consists of short repeated sequences of DNA.

 D. Pseudogenes never have introns.

 E. All pseudogenes contain Alu sequences.


9. Which of the following statements is NOT true?

 A. Prokaryotic chromosomes have multiple origins of replication.

 B. snRNAs have 5' Caps.

 C. Transfer RNA "decodes" the Genetic Code.

 D. rRNA has phosphate at its 5' end.

 E. Mitochondria use a unique DNA polymerase for replication.


10. Which of the following is NOT involved in translational initiation or elongation?

 A. tRNA synthetase.

 B. AUG codon.

 C. GTP.

 D. Shine-Delgarno sequence.

 E. EF-Tu.


11. Which of the following statements is FALSE?

 A. Metazoan DNA often contains repeated elements.

 B. Repeated DNA elements never have a function.

 C. Euchromatin tends to contain active genes.

 D. Histone modification can modulate gene transcription.

 E. Only a single histone H1 per nucleosome.


12. Which of the following is NOT a feature of nuclear mRNA splicing?

 A. Has a "lariat" intermediate.

 B. Requires the dinucleotides "GU" at the 5' end of the intron.

 C. Requires the signal AAUAAA in the mRNA.

 D. Is required prior to transport of most mRNAs from the nucleus to the cytoplasm.

 E. Is not required for histone mRNA formation.


13. Which of the following statements is NOT true of PCR?

 A. It is useful in the diagnosis of certain genetic disorders.

 B. It requires stringent laboratory precautions to ensure its validity.

 C. RT-PCR requires the use of the enzyme reverse transcriptase during cDNA synthesis.

 D. Use of thermostable DNA polymerases have greatly aided in its usefulness.

 E. Only one primer is required.


14. All the following RNAs have a 7-methyl guanosine cap EXCEPT:

 A. histone mRNA.

 B. the lac operon mRNA.

 C. the snRNA component of the U2 snRNP.

 D. ribosomal protein L17 mRNA.

 E. adenosine deaminase mRNA.


15. Which statement about mRNA splicing is FALSE?

 A. Intron sequences encode protein domains.

 B. Mechanism involves an unusual 5' to 2' nucleotide linkage.

 C. The second transesterification releases the lariat intermediate.

 D. snRNPs have a protein component.

 E. Exons are linked by phosphodiester bonds.


16. Which of the following most closely describes hnRNA?

 A. It participates directly in translation.

 B. It is the primary product of pol II transcription.

 C. It always contains introns.

 D. All hnRNA must be polyadenylated before it is translated.

 E. B and D.


17. Which of the following feature of eukaryotes serves the same function as the Shine-Delgarno sequence?

 A. 5' Cap.

 B. Pribnow box.

 C. Enhancer.

 D. Homeo box.

 E. Polyadenylation signal.


18. Which of the following proteins can introduce positive supercoils into DNA?

 A. Primosome.

 B. DNA ligase.

 C. Helicase.

 D. Single strand-binding protein.

 E. XPF protein.


19. A mutation that allows read-through of a stop codon during translation is called a ______ mutation.

 A. termination.

 B. transversion.

 C. amber.

 D. suppressor.

 E. silencer.


20. The gene for albumin is highly expressed in the liver; which of the following is LEAST likely about the chromatin near that gene?

 A. The albumin gene is in a region of euchromatin in liver.

 B. The DNA is highly methylated at pCpG sequences in the region.

 C. Histones are less abundant in the region.

 D. Histones are acetylated in the region.

 E. A and C.


21. Which of the following is NOT a general feature of enhancers?

 A. Distance independence.

 B. They are found in prokaryotes and eukaryotes.

 C. Orientation independence.

 D. The proteins that bind them generally function as dimers.

 E. B and C.


22. Which statement about the mRNA 5' cap is FALSE?

 A. Contains a methylated guanosine residue.

 B. Interacts with fMet-tRNA during translational initiation.

 C. Ribosomal RNAs do not have caps.

 D. Aids in ribosome-mRNA association.

 E. Has a free 3' hydroxyl group.


23. The first three nucleotides of a palindromic restriction endonodease recognition sequence are 5'-AAG-3'. What is the entire six basepair recognition sequence (both strands)?

 A. 5'-AAG-3'

 B. 5'-AAGCTT-3'

 C. 5'-AAGCTT-3'

 D. 5'-AAGGAA-3'

 E. None of the above.


24. You have determined that a strand of DNA is GC-rich. Its complementary strand is:

 A. AT-rich.

 B. pyrimidine-rich.

 C. purine-rich.

 D. GC-rich.

 E. cannot determine from the information given.


25. Which of the following is NOT required for DNA sequencing by the Sanger method?

 A. DNA polymerase.

 B. Reverse transcriptase.

 C. Oligonucleotide primer.

 D. dTTP & dCTP.

 E. Dideoxy adenosine triphosphate.


26. You have incorporated a radioactive "label" into a PCR primer. After 30 cycles of PCR, the radioactivity will be found:

 A. only in the original target DNA molecules.

 B. in 50% of the new DNA molecules.

 C. interspersed between the parent and child strands of both new DNA molecules.

 D. in 100% of the new DNA molecules.

 E. A and D.


27. Which statement most accurately describes restriction endonucleases?

 A. They fall into the helix-loop-helix family of DNA binding proteins.

 B. DNA methylases protect bacteriophage genomes from digestion.

 C. Useful restriction enzyme sites in the "polylinker" digest the plasmid only once.

 D. They require DNA ligase to complete their activity.

 E. Always cut within the lac Z gene.


28. Which of the following statements is FALSE about eukaryotic chromosome structure?

 A. Centromeres contain alphoid repeats.

 B. Protein scaffold required for complete compaction.

 C. High telomerase activity has been associated with some cancers.

 D. Mitochondrial chromosomes sometimes contain short telomeres.

 E. Mitochondrial genes sometimes use a different genetic code.


29. Which of the following proteins probably acts as a dimer?

 A. E. coli RNA polymerase.

 B. Histone H1.

 C. Cleavage stimulation factor.

 D. EF-Tu.

 E. The C/EBP enhancer binding factor.


30. Which of the following sets of components are required for enzymatic DNA sequencing?

 A. DNA, a primer, ATP, dideoxy nucleotides, DNA polymerase.

 B. DNA, a primer, dNTPs, dideoxy nucleotides, DNA polymerase.

 C. RNA, two primers, NTPs, dideoxy nucleotides, RNA polymerase II.

 D. RNA, two primers, NTPs, AZT, Taq polymerase.

 E. DNA, a primer, dNDPs, dideoxy ribonucleotides, RNA polymerase II.


31. Which of the following statements is FALSE?

 A. Hypervariable regions form the epitope of the antibody or T-cell receptor.

 B. An antibody can be secreted or exist as an integral membrane protein.

 C. IgA and IgG can form polymeric immunoglobulins in the presence of J-chain.

 D. DNA recombination events, involving widely separated DNA elements on the chromosome, are required for variable region domain formation of antibodies and T-cell antigen receptors, as well as heavy chain class switching events.

 E. IgM, the most abundant immunoglobulin, always appears first during the course of an immune response, followed by IgG during the secondary response.


32. Radioactive 32P is incorporated into the alpha phosphate position of ATP. Which of the following statements is TRUE?

 A. The radioactivity will be transferred to the retinoblastoma protein by the action of cyclinD-cdk4.

 B. The radioactivity will be removed from mRNA by the 5' capping reaction.

 C. The radioactivity will be incorporated into tRNA by eukaryotic RNA polymerase III.

 D. The radioactivity will be incorporated into DNA by the action of reverse transcriptase.

 E. The radioactivity will be incorporated into the Ras protooncogene by the action of Sos.


33. Increased plasma insulin can result in:

 A. increased adipocyte adenylate cyclase activity.

 B. decreased hepatocyte glucokinase

 C. decreased hepatocyte glycogen.

 D. decreased hormone sensitive lipase activity.

 E. decreased hepatocyte pyruvate dehydrogenase activity.


34. All the following substances are potentially mitogenic EXCEPT:

 A. Platelet-derived growth factor.

 B. Insulin.

 C. Exocrine factors.

 D. Contact inhibition.

 E. Steroid hormone.


35. A chronic alcoholic is admitted to your service with a blood pH of 7.2. Which of the following explains this finding?

 A. Ethanol is an acid that produces acidosis when consumed in large quantities.

 B. Ethanol is converted into lactic acid that will lower blood pH.

 C. Ethanol elevates the NADH concentrations in the liver causing an increased conversion of pyruvate to lactate.

 D. Ethanol decreases the respiratory rate leading to a buildup of CO2 that is converted to carbonic acid.

 E. Ethanol blocks electron transport causing a buildup of NADH and lactate.


36. Which immune response would be considered an immune system dysfunction?

 A. Successful vaccination against rabies virus.

 B. Organ transplant rejection.

 C. Immune response to influenza virus.

 D. An autoimmune response.

 E. Successful vaccination against poliovirus.


37. In uncontrolled type I diabetes mellitus, it would be expected that:

 A. blood pH would be greater than 7.4.

 B. excretion of keto-acids in the urine would decrease.

 C. gluconeogenesis by the liver will decrease.

 D. utilization of ketones by the brain will increase.

 E. lipolysis in adipose tissue will increase.


38. Glucagon plays a homeostatic role by:

 A. increasing in response to elevated blood glucose levels and then activating liver glycogen synthetase.

 B. increasing in response to lowered blood glucose levels and then activating liver glycogen phosphorylase.

 C. stimulating the release of glucose residues from muscle glycogen during intense exercise.

 D. activating adenylate cyclase in skeletal muscle cells.

 E. facilitating glucose uptake into skeletal muscle.


39. Which of the following is LEAST likely to activate a protooncogene?

 A. A point mutation in an enhancer.

 B. A deletion mutation that alters a diagnostic RFLP that is located 10 kb upstream.

 C. A mutation that removes a site of protein tyrosine phosphorylation.

 D. A translocation adjacent to a retroviral promoter.

 E. A point mutation in the regulatory protein domain.


40. The statements below are TRUE, EXCEPT which one?

 A. The immune system can directly mediate cytotoxicity to "foreign" cells by the complement cascade, by cytolysin or by perforin.

 B. The CD4 (or T4) T-cell protein also serves as the receptor for the HIV virus responsible for AIDS.

 C. Cytokines are produced when immune system cells become activated.

 D. The fundamental structural motif of the antibody is the so-called immunoglobulin fold, i.e., three beta-pleated sheets held together by disulfide bonds.

 E. Cytokines can assist the differentiation of cells of the immune system.


41. How are calcitonin and calcitriol similar?

 A. They both regulate serum calcium.

 B. They both mobilize calcium from bone.

 C. They both increase the synthesis of a calcium binding protein in the intestine.

 D. They both prevent mobilization of calcium from bone.


42. Which of the following are NOT tumor suppressors?

 A. Adenomatous polyposis coli (APC).

 B. Retinoblastoma.

 C. H-ras.

 D. BRCA1.

 E. p53.


43. All of the following are likely to occur after eating a large amount of carbohydrate EXCEPT:

 A. the synthesis of triacylglycerol in the liver.

 B. the synthesis of glycogen in the liver.

 C. increased pentose phosphate pathway activity in liver.

 D. release of glycerol from adipose tissue.

 E. the synthesis and release of VLDL from the liver.


44. All of the following are potential protooncogenes EXCEPT:

 A. the epidermal growth factor (EGF) receptor.

 B. histone H2B.

 C. a protein in the phospholipase C (PLC) signalling pathway.

 D. a protein that regulates DNA repair.

 E. a transcription factor that binds to a cyclin gene promoter.


45. Which of the following statements is TRUE about antigen-antibody reactions?

 A. They are not involved in allergic responses.

 B. They function to identify antigens for subsequent removal from the body.

 C. They occur because of the complementarity between epitope and parasite.

 D. They occur because of complementarity between alpha helices and beta turn structures.

 E. They only involve proteins.


46. The enzyme in liver that is stimulated first by glucagon is:

 A. phosphofructokinase

 B. glycogen synthase

 C. hormone sensitive lipase

 D. protein kinase A

 E. isocitrate dehydrogenase


47. Which of the following is NOT a feature of tumor suppressor genes?

 A. Are sometimes associated with familial cancers.

 B. Generally function to control cell growth.

 C. Rb controls the G1 breakpoint.

 D. Mutations in p53 are associated with 50% of all colon cancers.

 E. Only dominant mutations are observed.


48. Which statement below is TRUE about antibodies?

 A. Antibodies are normally made against nucleic acids.

 B. Antibodies all require J-chains.

 C. Antibodies are lipoproteins.

 D. Antibodies are cytokines produced by plasma cells.

 E. All antibodies are composed of heavy chains and light chains.


49. Which of the following reactions is needed for utilization of acetoacetate by EXTRAHEPATIC tissues?

 A. decarboxylation of acetoacetate to acetone.

 B. carboxylation of acetoacetate.

 C. reduction to beta-hydroxybutyrate.

 D. transfer of coenzyme A from succinyl CoA to acetoacetate.

 E. condensation with acetyl CoA to form HMG CoA.


50. 1,25-dihydroxycholecalciferol (calcitriol):

 A. is produced by the liver.

 B. inhibits resorption of calcium ions from bone.

 C. promotes intestinal synthesis of a calcium binding protein.

 D. reduces absorption of calcium from the kidney.

 E. synthesis is reduced by parathyroid hormone.


51. Which of the following is exhibited by diabetics WITHOUT insulin therapy?

 A. An increase in the rate of VLDL synthesis by the liver.

 B. An increase in the rate of oxidation of fatty acids by the liver.

 C. An increase in the rate of protein synthesis in muscle.

 D. An increase in the conversion of alanine to pyruvate in skeletal muscle.

 E. An increase in the use of acetone as energy by the brain.


52. Your patient has a genetic defect that blocks the synthesis of androstenedione. Which of the following will also be reduced by this defect?

 A. progesterone.

 B. testosterone.

 C. pregnenolone.

 D. cortisol.

 E. aldosterone.


53. Which of the following statements below is FALSE?

 A. Histocompatibility antigens are cell surface protein structures capable of presenting antigenic fragments to T-cells for specific recognition by T-cells.

 B. Class switching changes the immunoglobulin class, but not the paratope.

 C. Antibody paratopes result from the juxtaposition six hypervariable regions, three each from the light chain and the heavy chain variable domains.

 D. B-cells synthesize heavy chains, light chains and secretory piece.

 E. The five major immunoglobulin classes are IgM, IgG, IgD, IgE, and IgA.


54. Which of the following statements are TRUE about the cell cycle?

 A. cdk's require cyclins for their activities.

 B. phosphorylation of the retinoblastoma protein by cycD-cdk4 allows cells to pass the G1 checkpoint.

 C. Some cells can reenter G1 phase from G0 phase.

 D. DNA content during G2 is 4N.

 E. All of the above.


55. In the fed state:

 A. glucose is both converted to glycogen and stored in skeletal muscle.

 B. adipose tissue converts triglycerides to glucose.

 C. amino acids are transaminated to form ketone bodies.

 D. glycogen stores in liver are depleted.

 E. glycogen phosphorylase is in the active form.


56. Which of the following statements is FALSE?

 A. Immunogens are normally viewed as foreign by the immune system.

 B. Antigens are almost always high molecular weight lipids or carbohydrates.

 C. Antigens can be parts of parasites, bacteria or viruses.

 D. Epitopes of proteins are generally five to six amino acids in size.

 E. Antigens have small topological features called epitopes.


57. Chronic alcohol consumption:

 A. leads to decreased NADH production in the cytosol and mitochondria.

 B. leads to hyperglycemia because alcohol is converted to glucose.

 C. leads to decreased rates of inactivation of drugs by cytochrome P450.

 D. leads to decreased concentrations of pyruvate in the liver.

 E. leads to increased chylomicron production by the liver


58. All of the statements below about T-cells are TRUE, EXCEPT which one?

 A. The T-cell antigen receptor specifically recognizes the antigen fragment carried by the major histocompatibility complex class I protein.

 B. The major histocompatibility complex class I protein is recognized by the CD8 (or T8) protein of the cytotoxic T-cell.

 C. The T-cell antigen receptor is a heterodimeric protein with variable region domains and constant region domains.

 D. The major histocompatibility complex class II protein is recognized by the CD4 (or T4) protein of the helper T-cell.

 E. The CD3 complex of the T-cell carries and displays the antigen fragment.


59. Found in, or characteristic of, brain tissue:

 A. glucokinase

 B. glucose 6-phosphatase

 C. major site of lipolysis

 D. major site of conversion of lactate to glucose

 E. can metabolize ketone bodies for energy


60. Twenty four hours after a meal, the primary source of glucose carbons for the brain is:

 A. dietary glucose.

 B. muscle glycogen.

 C. glycerol from adipose tissue.

 D. fatty acids.

 E. skeletal muscle protein.


Key Answer

1. D

11. B

21. B

31. E

41. A

51. B

2. D

12. C

22. B

32. C

42. C

52. E

3. C

13. E

23. B

33. D

43. D

53. D

4. D

14. B

24. D

34. D

44. B

54. E

5. B

15. A

25. B

35. B

45. B

55. A

6. A

16. B

26. D

36. D

46. D

56. B

7. A

17. A

27. C

37. E

47. E

57. D

8. A

18. C

28. D

38. B

48. E

58. E

9. A

19. D

29. E

39. B

49. D

59. E

10. A

20. B

30. B

40. D

50. C

60. E





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