Biochem Post Test

Biochemistry Choose the best answer: ___1. Which among the following lipoproteins is inversely related to the incidence of coronary atherosclerosis? A. Chylomicrons B. HDL C. LDL D. VLDL ___2. In the shuttle of mitochondrial acetyl coenzyme A to the cytosol for fatty acid synthesis, in which step generates NADPH? A. Oxaloacetate + acetyl coenzyme A  citrate B. Oxaloacetate  malate C. Malate  pyruvate D. Pyruvate  oxaloacetate ___3. The lipoprotein that serves to transport triacyglycerol from the liver to the different extrahepatic tissues. A. Chylomicrons B. HDL C. LDL D. VLDL ___4. In the following steps in ketone bodies metabolism, NADH is generated in: A. Acetoacetate  acetone B. Acetoacetate  beta hydroxybutyrate C. Acetoacetyl coenzyme A + acetyl coenzyme A  HMG CoA D. Beta hydroxybutyrate acetoacetate ____5. Human body synthesize cholesterol de novo from acetyl coenzyme A. Cholesterol synthesis occurs in which of the following organelles? A. Cytosol B. endoplasmic reticulum C. mitochondria D. ribosomes ___6. Which among the following conditions is characterized by abnormal accumulation of galactocerebroside in the affected tissues? A. Farber’s disease B. Fabry’s disease C. Krabbe’s disease D. Gaucher’s ___7. Which of the following lipoproteins has the highest triacylglycerol content? A. Chylomicrons B. HDL C. LDL D. VLDL ___8. Ketone bodies maybe synthesized from fatty acids by which of thefollowing organs or cells? A. Skeletal muscle B. liver C. kidney D. erythrocytes ___9. Spontaneous decarboxylation of acetoacetate results in the formation of: A. Acetone B. acetyl coenzyme A C. 3-hydroxybutyrate D. propionate ___10. The major site of fatty acid synthesis. A. Mammary gland B. liver

C. adipose tissue

D. Kidney

___11. Which among the following is accumulated in tissues of patient with Tay-Sach’s disease? A. Ceramide trihexoside B. galactocerebroside sulfate C. ganglioside D. sphingomyelin ___12. In the biosynthesis of fatty acids, what is the compound that transports the acetate group out of the mitochondria into the cytoplasm? A. Pyruvate B. malate C. citrate D. acyl carnitine ___13. The committed step in fatty acid synthesis is the formation of: A. Malonyl coenzyme A B. Acetyl coenzyme A C. Acety acyl carrier protein D. Malonyl acyl carrier protein

___14. I n the complete oxidation of one (1) mole of palmitic acid to CO 2 and H2O, the total number of ATP generated is: A. 12 B. 24 C. 131 D. 129 ___15. Which of the following is a C-19 steroid? A. Cholic acid b. cortisol C. estradiol ___16. Which of the following is C-24 steroid? A. Chenodeoxycholic acid B. cortisol

D. testosterone

C. estradiol D. progesterone

___17. Which among the following is an essential requirement for triacyglycerol synthesis in the adipose tissue? A. Adrenaline B. cortisol C. glucagon D. insulin ___18. Which among the ketones bodies is not a source of fuel in the extrahepatic tissues like the heart muscle? A. Acetoacetic acid B. acetone C. beta-hydroxybutyric acid D. ketoacids ___19. Which of the following is the end product of extramitochondrial lipogenesis? A. Oleic acid B. palmitic acid C. palmitoleic acid D. stearic acid ___20. Which of the following is the committed step in beta oxidation? A. Activation of fatty acid B. Oxidative step C. Carnitine transport D. Ketothiolysis ___21. Which of these enzymes catalyze the rate-limiting step in cholesterol synthesis? A. HMG-CoA synthase C. HMG-CoA reductase B. HMG-CoA oxidase D. HMG-CoA acetylase ___22. All sphingolipids are synthesized from which of the following precursors? A. Glycerol B. phosphatidic acid C. ceramide D. cholesterol ___23. Acetyl CoA for extramitochondrial palmitate synthesis is derived from this Kreb’s citric acid cycle intermediate: A. Malate B. succinate C. citrate D. alpha-ketoglutarate ___24. The main source of NADPH for lipogenesis: A. Glycolysis B. HMP shunt C. polyol pathway

D. uronic acid pathway

___25. Beta-oxidation is inhibited in the fed state because malonyl CoA which arises from acetyl CoA inhibits: A. Acetyl CoA carboxylase C. carnitine palmitoyl transferase 1 B. Acyl CoA dehydrogenase D. Thiolase ___26. What is the possible role of modified histones? A. methylation of histones is correlated with activation and repression of gene transcription. B. Sumoylation of histones leads to transcription activation C. Phosphorylation of histones H3 and H4 is associated with the condensation of chromosomes during the replication cycle D. Acetylation of histone H1 is associated with chromosomal assembly during DNA replication

___27. Which is considered as transcriptionally active chromatin A. B. C. D.

euchromatin heterochromatin constitutive chromatin telomeres

___28. This is the noncoding intervening sequence. A. B. C. D.

exon intron kinetochore telomeres

___29. This is the enzyme responsible DNA unwinding during replication A. B. C. D.

DNA ligase Helicase DNA polymerase Topoisomerase

___30. Eukaryotic RNA polymerase II synthesizes: A. B. C. D.

rRNA mRNA tRNA sn RNA

___31. Which one is responsible for splicing reactions of mRNA A. B. C. D.

“snurp” Ribozyme RNA polymerase DNA polymerase

___32. Part of DNA template where transcription is to commence. A. B. C. D.

promoter repressor enhancer terminator

___33. The genetic code is characterized as: A. B. C. D.

non-degenerate non-overlapping species-specific non-specific

___34. Type of DNA mutation where there is replacement of purine with a pyrimidine . A. B. C. D.

transition transversion silent mutation full mutation

___35. The total DNA of a cell line or tissue. A. Genomic DNA library B. cDNA library

C. introns D. exons ___36. Complementary DNA copies of the population of mRNAs in a tissue. A. B. C. D.

Genomic DNA library cDNA library introns exons

___37. The entire collection of expressed mRNAs in an organism. A. B. C. D.

RNA clone cDNA library genomic DNA library transcriptome

_C__38. Mutation of this genes will lead to loss of the integrity of the genome: A. Oncogenes

B. Tumor suppressor genes

C. Mutator genes

D. protooncogenes

_B__39. Mutation of this gene confer chemoresistance in cancer: A. pRB

B. p53

C. ras gene D. mismatch repair gene

_B__40. Human papilloma viral infection causes overexpression of E6 which facilitates the Degradation of: A. pRB

B. p53

C. mutator gene

D. protooncogene

D. A/C

_____41. Storage molecule of genetic information: A. DNA B. RNA C. Both D. Neither _____42. RNA and DNA differ from each other: A. In DNA, the nucleotides run 5’ to 3’ direction B. In RNA, the sugar is linked to the base by an N-glycosidic linkage C. In RNA, the sugar is d-ribose D. In DNA, thymine is found instead of uracil _____43. A Pyrimidine BASE A. Adenine B. Guanine

C. Uracil

D. cytidine

E. C and D

_____44. Serves as transporter of amino acid to the site of protein synthesis A. mRNA B. tRNA C. rRNA D. micro RNA _____45. Hyperchromicity effect is observed in: A. DNA renaturation B. DNA denaturation

C. dsDNA

____46. Which among the following is not a nucleoside? A. Adenosine B. guanosine C. cytosine

D. RNA

D. Thymidine

_____47. Nucleotide derivative that acts as” second messenger”. A. ATP B. ADP C. cAMP D. GTP E. UDP ____48. If the adenine content of a double-helical DNA is 20% of the total bases, the cytosine content would be: A. 20% B. 30% C. 40% D. 50% E. 60% ____49. What is the predominant form of DNA in the cell? A. A-DNA B. B-DNA C. C-DNA

D. Z-DNA

____50. Which form is favored at low humidity? A. A-DNA B. B-DNA C. C-DNA _____51. Watson-Crick base pairs: A. Adenine pairs with uracil A. Adenine pairs with thymine B. Guanine pairs with cytosine

D. Z-DNA

D. A/B/C E. B/C

_____52. Factors that can cause DNA denaturation: A. High temperature B. Alkaline pH

C. Both

D. Neither

_____53. Which among the following is the most condensed form of DNA? A. Beads on a string B. 10nm fiber C. 30nm fiber D. naked DNA _____54. This molecule has cap and a tail: A. rRNA B. mRNA

C. tRNA

D. DNA

_____55. This molecule has the anti-codon A. mRNA B. tRNA

C. rRNA

D. micro RNA

_____56. Salvage pathways of nucleotide metabolism: A. utilizes free bases as substrates for nucleotide biosynthesis B. takes place in the ribosomes C. derives its ring components from amphibolic intermediates D. is most efficient than the de novo pathway ____57. The enzyme that catalyzes the committed step in purine de novo pathway: A. xanthine oxidase B. PRPP synthetase C. PRPP glutamylamido transferase D. HGPRTase _____58. Xanthine oxidase inhibitor: A. Colchicines B. Methotrexate C. Allopurinol D. Acetaminophen _____59. The first purine nucleotide synthesized by the de novo pathway: A. AMP B. GMP C. IMP D. OMP _____60. Major source of ribose for nucleotide biosynthesis: A. HMP shunt B. Meister’s cycle C. Glycolysis

D. Kreb’s cycle

____61. Protein digestion starts in the: A. Mouth where the amylase can be found B. Stomach where the acidic environment favors denaturation C. Intestines where proteolytic enzymes are abundant D. All of the above

____62.The following statement(s) is/are TRUE about protein turnover:

A. B. C. D.

Proteins that are important in metabolic regulation are generally short-lived Protein turnover takes place constantly in cells Ubiquitin tap the protein for destruction All of the above

____63. The highest protein structural organization assumed by both functional hemoglobin and immunoglobulin molecules: A. Primary structure C. secondary structure B. Tertiary structureD. quarternary structure ____64. The major mechanism of detoxification of ammonia in the brain tissue is the formation of: A. Alpha-ketoglutarate C. succinate B. Glutamine D. urea ____65. In amino acid catabolism, which of the following is a correct pair as to clinical disorder and its associated deificient enzyme? A. Absence of alpha-branched chain keto acid decarboxylase- Richner Hanhart syndrome B. Ornithine transcarbamoylase deficiency –Hyperammonemia type 1 C. Hydroxyphenylpyruvate hydroxylase deficiency –Classic phenylketonuria D. Lack of homogentisate oxidase – Alkaptonuria ____66. Which of the following amino acid functional group pairs is not correct? A. Arginine:guanidine B. Histidine:imidazole C. Phenylalanine:hydroxyphenyl D. Tryptophan:indole E. Csyteine:sulfhydryl ____67. Helical formation or helix is a characteristics of what protein structure? A. Primary B. Secondary C. Tertiary D. Quarternary ____68. Among the following amino acids, which one is converted to pyruvate through transamination reaction? A. Alanine B. Methionine C. Threonine D. Valine ___69. Which of the following amino acids is convertible to pyruvate by direct deamination? A. Alanine B. Cysteine C. Glycine D. Serine

____70. The amino acid precursor of catecholamines:

A. B. C. D. E.

Glycine Proline Threonine Tryptophan Tyrosine

____71. Among the following amino acids, which one is purely ketogenic? A. Isoleucine B. Leucine C. Phenylalanine D. Threonine E. Tryptophan ____72. Urea is the major pathway of nitrogen excretion in humans. It is synthesized in the : A. Brain B. Intestine C. Kidney D. Liver E. Skeletal muscle ____73. Among the intermediates in urea cycle, which one provides the linkage of urea cycle and the citric acid cycle? A. Alpha ketoglutarate B. Aspartate C. Fumarate D. Malate E. Oxaloacetate ____74. Amino acid precursor of serotonin A. Alanine B. Aspartate C. Tryptophan D. Methionine E. Tyrosine ____75. Which of the following is a non essential amino acid? A. Leucine B. Tyrosine C. Lysine D. Methionine E. Valine ____76. Anaerobic glycolysis produces how many moles of ATP per mole of glucose? A. 2 B. 6 C. 8 D. 12 E. 24 ____77. Rate limiting enzyme and the major regulatory enzyme in glycolysis: A. Triose phosphate isomerase B. Glyceride 3-phosphate dehydrogenase C. Phosphofructokinase D. Aldolase

____78. Enzyme that links glycolysis and the citric acid cycle

A. B. C. D.

Pyruvate dehydrogenase Isocitrate dehydrogenase Alpha-ketoglutarate dehydrogenase Succinate dehydrogenase

____79. Insulin stimulates which of the following metabolic pathways? A. Glycogenolysis C. gluconeogenesis B. Glycolysis D. lipolysis ____80. Which is not an intermediate of the Kreb’s cycle? A. Isocitrate C. Succinate B. Pyruvate D. Malate ____81. Which enzyme reverses the hexokinase reaction in the liver during fasting to liberate free glucose into the blood? A. Glucose-6-phosphatase C. Pyruvate carboxylase B. PEP carboxykinase D. Fructose 1,6-bisphosphatase ____82. Which of the following enzymes is common to both glycolysis and gluconeogenesis? A. Pyruvate carboxylase C. Phosphoglycerate kinase B. Hexokinase D. Fructose 1,6-bisphosphatase ____83. The major metabolic product under normal circumstances by RBC and by the muscle cells during intense exercise is recycled through the liver in the Cori cycle. The metabolite is: A. Oxaloacetate C. Alanine B. Glycerol D. Lactate _____84. In starvation,glucagon induces the formation of which of the following enzymes in carbohydrate metabolism: A. Phosphofructokinase-1 B. Pyruvate kinase C. Fructose 1,6 bisphosphatase D. Phosphoenolpyruvate carboxykinase _____85. The chief constituent of fibrous part of plants, is: A. Starch B. Cellulose C. Chitin

D. peptidoglycan

_____86. A sugar alcohol that is implicated in the causation of cataract in galactosemia, is: A. Mannitol B. Galactitol C. Sorbitol D. A/B/C _____87. TRUE regarding sucrose: A. It has a free carboxyl group B. It is non-reducing sugar

C. It is also known as sucrose D. A/B/C

_____88. D-glucose and D-mannose are: A. Anomers B. epimers C. enantiomers

D. none of the above

_____89. Glycolysis, glycogenesis and lipogenesis are stimulated by this hormone: A. Glucagon B. Insulin C. Cortisol D. epinephrine

_____90. It is an amphibolic pathway and regarded as the final common pathway of metabolism: A. Embden-Meyerhof pathway C. Glycogenesis B. Citric acid cycle D. Kreb’s-Henseleit cycle _____91. The energy generation phase of glycolysis starts with this reaction: A. Conversion of glucose to glucose-6-phosphate B. Conversion of fructose to fructose-6-phosphate C. Conversion of fructose-6-phosphate to DHAP and glyceraldehydes-3phosphate D. Conversion of glyceraldehydes-3-phosphate to 1,3-diphosphoglycerate _____92. Complete oxidation of one mole of glucose using the malate aspartate shuttle will yield how many moles of ATP ( net): A. 40 B. 38 C. 36 D. 24 E. 12 ____93. This cycle recycles lactate formed in the muscles back to glucose in the liver: A. Anaerobic glycolysis C. Cori cycle B. Uronic acid pathway D. Glucose-alanine cycle ____94. Storage form of glucose in animals: A. Starch B. polysaccharides

C. glycogen

D. A/B/C

____95. Gluconeogenesis is the process of: A. Transformation of non-glucose substrates into glucose B. Breakdown of glycogen into single glucose units C. Breaking glucose into energy D. A/B/C Matching type: A. B. C. D. E. F.

Methotrexate Trimethoprim Azaserine Sulfa drugs Colchicine Allopurinol

B____96. Inhibits dihydrofolate reductase in bacterial cells C____97. Inhibits incorporation of N3 and N9 in the purine ring D____98. PABA analogue/pteridine ring inhibitor A____99. Inhibits reduction of dihydrofolate to tetrahydrofolate E____100. Inhibits tuibulin in PMN’s END OF EXAM GOOD LUCK!!!