1.Insulin production by ß-cells of the pancreas involves each of the following processes
EXCEPT:
A.Glycosylation of the polypeptide
B.Packaging of the hormone in secretory granules
C.Removal of the signal peptide and formation of disulfide bonds to form proinsulin
D.Removal of the C-peptide
E.Transcription of mRNA encoding pre-proinsulin
2.Cholera toxin causes massive and often fatal diarrhea by:
A.Inactivating Gi protein
B.Irreversibly activating adenylate cyclase
C.Locking Gs protein into an inactive form
D.Rapidly hydrolyzing G protein GTP to GDP
E.Inhibition of guanylate cyclase
3. All of the following are true of nitric oxide EXCEPT:
A. Its synthesis is increased by the drug Viagra
B. It activates guanylate cyclase
C. It is a gaseous signaling molecule that can diffuse from one cell to another
D. It results in relaxation of smooth muscle
E. Its nitrogen atom comes from arginine
4. A cell population in culture is treated with a membrane-permeable analog of cyclic AMP in the absence of hormone treatment. What is themost likely effect of adding this compound?
A.Activation of a G protein
B.Activation of protein kinase A
C.Binding of arrestin to a receptor
D.Activation of adenylate cyclase
E.Activation of protein kinase C
I
5.Which of the following is TRUE of proteoglycans and glycoproteins?
A.The polysaccharide component of both proteoglycans and glycoproteins can be branched
B.The polysaccharide component of both proteoglycans and glycoproteins can be elongated in the Golgi
C.Polysaccharides can be linked to protein via asparagine for both proteoglycans and
glycoproteins
D.Polysaccharides of both proteoglycans and glycoproteins can contain sialic acid
E.Polysaccharides of glycoproteins are made up of repeating disaccharide units while the
polysaccharides of proteoglycans are more complex
6. All of the following molecules contain carbons obtained from the tetrahydrofolate one-carbon pool EXCEPT:
A.The purine ring
B.Methylcobalamin
C.dTMP
DThe pyrimidine ring
ESerine
7. The major regulatory step in the biosynthesis of cholesterol involves formation of:
A. Squalene
B. Lanosterol
C. Mevalonate
D. Hydroxymethyl-glutaryl CoA
E. Acetoacetyl CoA
8. Which of the following provides carbon atoms in the biosynthesis of the pyrimidine base structure?
A. Aspartate
B. Glycine
C. Glutamine
D. Serine
E. S-Adenosylmethionine
9. Insulin binds its receptor on the plasma membrane to regulate cell metabolic activity. All of the following statements about the insulin receptor are true EXCEPT:
A. The receptor is composed of polypeptide chains joined by disulfide bonds
B. Insulin binding to the receptor activates a tyrosine kinase domain in the receptor
C. The receptor is internalized into the cell following insulin binding
D. The receptor requires a trimeric G protein for signaling
E. The receptor undergoes autophosphorylation
10. Which of the following statements concerning vitamin B12 is FALSE?
A. It is enriched in animal by-products
B. It is used in the conversion of methylmalonyl CoA to succinyl CoA
C. It is utilized in the direct formation of methionine from homocysteine
D. It binds intrinsic factor that is produced by parietal cells
E. It is utilized in the direct formation of cystathionine from homocysteine
11.A young child is in an automobile accident that requires surgical intervention and substantial recovery time in the hospital. Consultation with a nutritionist results in a specific dietary plan that includes supplementation with an amino acid typically considered to be non-essential. Which of the following amino acids is an essential amino acid under conditions of enhanced growth or surgical recovery?
A. Alanine
B. Arginine
C. Glycine
D. Serine
E. Tyrosine
12. The major function of HDLs is to:
A. Transport cholesterol to peripheral tissue
B. Promote recycling of the LDL receptor
C. Bind cholesterol released from peripheral cell membranes
D. Transport dietary triglycerides to intestinal epithelial cells
E. Activate cholesterol esterification by acyl-CoA:cholesterol acyltransferase (ACAT)
13. All of the following statements about phosphatidylethanolamine are trueEXCEPT:
A. Can be made by decarboxylation of phosphatidylserine
B. Can be used to make phosphatidylserine by displacement of ethanolamine by serine
C. Can be converted to phosphatidylcholine by methylation
D. Can be used to make phosphatidylcholine by displacement of ethanolamine by choline
E. Can be used to produce ethanolamine from an amino acid in a net fashion
14. The major function of the LDL receptor is to:
A. Mediate the uptake of LDLs into cells
B. Transfer cholesterol esters from LDLs to HDLs
C. Transfer cholesterol esters from the cytoplasm to the plasma membrane
D. Prevent conversion of cholesterol to cholesterol esters
E. Recycle apoproteins from LDLs back to HDLs
15. Before the introduction of vitamin D-fortified milk, children who spent most of their time
indoors often developed rickets. In these vitamin D-deficient children, the most likely
explanation for their bone malformations is:
A. Excessive deposition of calcium in bone
B. Excessive renal excretion of phosphate ion
C. Inadequate uptake of calcium in the intestine
D. Lack of weight-bearing exercise
E. Excessive renal tubular reabsorption of calcium
16. The most direct route to cardiolipin biosynthesis is:
A. Phosphatidylglycerol + phosphatidic acid
B.CDP-glycerol + phosphatidylglycerophosphate
C. CDP-diacylglycerol + phosphatidylglycerol
D.Phosphatidylinositol + phosphatidylglycerol
E.Diacylglycerol + ATP + glycerol phosphate
17. A patient presents with extreme swelling and tenderness in the joints of the extremities. Examination of synovial fluid extracted from a big toe reveals the presence of urate crystals and confirms the diagnosis of gouty arthritis. The drug allopurinol is prescribed in order to inhibit which of the following enzymes?
A. Adenosine deaminase
B. AMP deaminase
C. Nucleoside phosphorylase
D. Uricase
E. Xanthine oxidase
18. All of the following play an important role in biosynthesis of many integral membrane proteins EXCEPT:
A. Clathrin
B. Signal recognition particle
C. Chaperones
D. GTP
E. ATP
19. A patient presents in your office with very high levels of serum cholesterol despite following the diet and exercise regimen you prescribed last year. You decide that this patient would benefit from a drug such as Lipitor (atorvastatin). This class of drugs is effective in treating hypercholesterolemia because it:
A. Stimulates phosphorylation of ß-hydroxy-ß-methylglutaryl-CoA reductase
B. Increases degradation of ß-hydroxy-ß-methylglutaryl-CoA reductase
C. Binds cholesterol and prevents it from being absorbed by the intestinal mucosa
D. Directly prevents the deposition of cholesterol on artery walls
E. Inhibits ß-hydroxy-ß-methylglutaryl-CoA reductase
20. All of the following statements regarding the water-soluble vitamins are true EXCEPT:
A. Many electron transfer reactions use cofactors derived from Vitamins B2 or B3 (riboflavin and niacin)
B. Vitamin B1 (thiamine) is a precursor for a catalytic component of alpha-ketoglutarate dehydrogenase
C. Excess amounts of water-soluble vitamins are usually excreted in the urine
D. Biotin is used to carry C1 units at the same oxidation level as that in S-adenosyl methionine
E. Deficiency in Vitamin C (ascorbate) disrupts modification of proline residues in connective tissue protein
21. All of the following statements about genetically inherited defects are true EXCEPT:
A. Hunter syndrome is due to deficient degradation of a glycosaminoglycan in the lysosomes
B. I-cell disease results in impaired targeting of extracellular proteins to the lysosomes for degradation
C. Leukocyte adhesion deficiency Type II results in improper modification of the carbohydrate portion of glycoproteins
D. Tay-Sachs disease results in accumulation of a ganglioside in the lysosomes
E. Niemann-Pick disease results in accumulation of sphingomyelin in the lysosomes
22. Which of the following statements about the fat-soluble vitamins is TRUE?
A. Excess Vitamin A is oxidized in the liver for excretion as a component of bile
B. In most people, exposure of the skin to sunlight decreases the amount of Vitamin D needed in the diet
C. A major function of Vitamin E (tocopherol) is to facilitate electron transfer from NADH to oxygen in the mitochondrial membrane
D. Vitamin K is required for activation of clotting factors by carboxylation of selected aspartate residues
E. Regulation of bone mineralization is disrupted by Vitamin A deficiency
23. The ionophore valinomycin greatly increases the permeability of K+ across membranes by acting as a carrier for the ion. This action requires diffusion in the membrane. Which ONE of the following is most likely to INCREASE valinomycin-mediated K+ flux across the membrane?
A. A decrease in temperature
B. A decrease in average chain length of fatty acid residues of membrane lipids
C. An increase in saturated fatty acid residue content of membrane lipids
D. An increase in carbohydrate residue content of membrane proteins
E. A decrease in the content of essential fatty acyl residues in membrane lipids
24. Which of the following best describes the mechanism by which cholesterol (or a metabolite) represses the expression of enzymes involved in cholesterol biosynthesis?
A.It acts directly as a transcription factor
B. It directly inhibits a protease that releases a transcription factor
C. It binds to the Steroid Regulatory Element Binding Protein (SREBP) and inhibits its action
D. It prevents the movement of the pre-SREBP from the endoplasmic reticulum to the Golgi
25. Trace amounts of 3H-thymidine were added for 2 hours to a nonsynchronized culture of cells doubling in number every 24 hours. Then, unincorporated label was removed by washing and radioactivity was visualized by autoradiography of cells fixed on coverslips. Which one of the following is most likely to be observed?
A.Radioactivity is present in nuclei of all cells
B. Radioactivity is present in the cytoplasm of all cells
C. Radioactivity is present in the nuclei of 10-30% of the cells
D. Radioactivity is present in the cytoplasm of 10-30% of the cells
E. No radioactivity is incorporated
26. All of the following statements concerning apoptosis are true EXCEPT:
A. A proteolytic cascade is activated
B.It can involve release of a mitochondrial protein into the cytoplasm
C. It can be triggered by ligand binding to the cell surface
D. Nuclear DNA remains intact after apoptosis is triggered
E. Apoptosis is required for normal embryological development
27. Which of the following statements about serine is FALSE:
A. It contributes carbon to the one-carbon pool
B. It is a three carbon amino acid formed from 3-phosphoglycerate
C.It is converted to glycine by a reaction requiring tetrahydrofolate
D.It controls its own production by feedback inhibition of 3-phosphoglycerate dehydrogenase
E.It is synthesized from glucose via an intermediate of the TCA cycle
28. All of the following statements about sialic acid (N-acetyl neuraminic acid) are true EXCEPT:
A. It is present in gangliosides but absent from cerebrosides
B. Its attachment to some molecules regulates their lifetime in the circulation
C. It can be a component of both glycolipids and glycoproteins
D.It is formed by isomerization of glucuronic acid
E. It is removed by enzymes in the lysosome
29. Which ONE of the following acts directly to trigger release of Ca2+ from the endoplasmic reticulum?
A. Diacylglycerol
B. Inositol trisphosphate (IP3)
C. Cyclic AMP
D.Protein kinase C
E.Calmodulin
30. Sphingolipids:
A. Contain a backbone that derives its carbons from condensation of palmitic acid and glycine
B. Have two fatty acyl chains, one as an amide, one as an ester
C. Are conjugated with taurine prior to entering the gut
D. Are stored with triglycerides in intracellular lipid droplets
E. Can be sulfated using an adenosine-based carrier molecule
31. All of the following are important functions of bile acids and bile salts EXCEPT:
A.Help to dissolve biliary cholesterol
B. A significant component of chylomicrons
C. Absorption of fat-soluble vitamins
D.Emulsify triglycerides taken in the diet
E. Removal of cholesterol from the body
32. Which one of the following statements about heme biosynthesis is TRUE?
A.Some carbons of heme are furnished by S-adenosyl methionine
B. Defects in the enzymes of heme biosynthesis are usually asymptomatic in heterozygotic individuals
C. Accumulation of heme biosynthetic intermediates can result in photosensitivity
D. The iron atom is inserted before the porphyrin ring is closed
E. All steps in heme biosynthesis take place in the cytoplasm
33. A patient presents in your office with very high levels of serum cholesterol. After a series of tests you conclude that the patient has elevated LDL cholesterol, but has normal levels of liver LDL receptor. The most likely explanation for this situation is:
A. Dysfunctional apoprotein B-100
B. Inability to remove cholesterol from the LDL complex
C. Defective lipoprotein lipase
D. Decreased acyl-CoA:cholesterol acyltransferase activity
E. Altered phosphorylation of the LDL receptor
34. All of the following statements about O-linked glycoproteins are true EXCEPT:
A. The carbohydrate component can be branched and can contain many different
monosaccharides
B. The carbohydrate is attached directly to a growing oligosaccharide linked to the protein through either serine or threonine
C. Activated sugars are added one at a time to the protein in the endoplasmic reticulum
D.Degradation of both the protein and polysaccharide components occurs in lysosomes
E. The oligosaccharide component of O-linked glycoproteins in the plasma membrane faces the extracellular matrix
35. Which of the following is NOT found as a major constituent in biological membranes?
A. Sphingomyelin
B. Cholesterol
C. Free fatty acids
D. Phosphatidylcholine
E. Phosphatidylethanolamine
36. Which of the following statements concerning tyrosine is FALSE:
A. It is the product of phenylalanine hydroxylase
B. It is used together with glycine in the formation of creatine
C.It is utilized in the formation of epinephrine
D. It is an essential amino acid in patients with phenylketonuria
E. Its formation utilizes tetrahydrobiopterin
37. All of the following statements regarding iron metabolism are true EXCEPT:
A. Ferritin is the major storage form of iron
B. Iron is transported in the bloodstream as ferrous ion (Fe2+) complexed with transferrin
C. Iron uptake by peripheral cells is limited by the number of transferrin receptors at the cell surface
D. Reactive oxygen species can be produced in reactions involving iron
E. Mobilization of stored iron and its transport in the bloodstream requires both oxidation and reduction of the iron
38.All of the following statements about N-linked glycoproteins are true EXCEPT:
A. The carbohydrate component contains a common oligosaccharide made up of mannose and N-acetyl glucosamine (G1cNAc)
B. Synthesis of the carbohydrate component can occur in both the endoplasmic reticulum and the Golgi
C. Elongation of the protein-linked oligosaccharide in the Golgi requires
sugar-nucleotide:nucleotide antiporters
D. Dolichol phosphate shuttles activated sugars from the cytoplasm into the endoplasmic reticulum lumen
E.The polysaccharide chain remains attached to the protein during degradation in the lysosomes
39. Conversion of nucleoside diphosphates to deoxynucleoside diphosphates is carried out by:
A. Dihydrofolate reductase
B. Ribonucleotide reductase
C. Xanthine oxidase
D.Hypoxanthine-guanine phosphoribosyltransferase
E. Dihydropteridine reductase
40. Which of the following reactions requires S-adenosylmethionine as a methyl donor?
A. Formation of 5, 10-methylene-FH4 from serine
B. Methylation of homocysteine to form methionine
C. Formation of epinephrine from norepinephrine
D. Methylation of dUMP to form dTMP
E. Formation of creatinine from creatine phosphate
41. Cystic fibrosis is a common inherited disease in the Caucasian population. The product of this gene (CFTR) exhibits all of the following properties EXCEPT:
A. It is a member of a large superfamily of ATP-binding proteins
B. It is an integral membrane protein with 2 ATP-binding sites
C. It is a chloride channel
D. It derives energy from a Na+ gradient
E. It is insensitive to cardiac glycosides such as digitalis
42. All of the following statements concerning synthesis of thyroid hormones are true EXCEPT:
A. Tyrosine is iodinated before it is incorporated into thyroglobulin
B. Iodination occurs in a colloid extracellular space
C. Active hormone is released by proteolysis of a precursor stored in intracellular vesicles
D.Active hormone contains either three or four iodine residues per molecule
E. Iodide is actively accumulated by the thyroid gland
43. Diacylglycerol is a necessary intermediate on the biosynthetic path to all of the following EXCEPT:
A. Phosphatidylcholine
B. Triacylglycerol
C. Phosphatidylethanolamine
D.CDP-diacylglycerol
E. Phosphatidylserine
44. All the following statements about cyclooxygenase activity are true EXCEPT:
A. Forms a precursor of leukotrienes
B. Can be inhibited by aspirin
C. Catalyzed by two distinct isoenzymes
D.Forms a precursor of prostacyclin
E.Important in inflammation and hemostasis
45. All of the following statements regarding polyamines are true EXCEPT:
A. They obtain carbons from glutamate
B. Their synthesis involves the decarboxylation of ornithine
C. They obtain carbons and nitrogen from serine
D. They are highly cationic molecules
E. They play important roles in cell growth and differentiation
46. All of the following are characteristic of facilitated diffusion EXCEPT:
A. Saturation kinetics as a function of substrate concentration
B. Inhibition by structural analogs of substrate
C. Stereospecificity
D. Movement of substrate against its concentration gradient
E. Can be lost by genetic mutation
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Answers
1. A
2. B
3. A
4. B
5. B
6. D
7. C
8. A
9. D
10. E
11. B
12. C
13. D
14. A
15. C
16. C
17. E
18. A
19. E
20. D
21. B
22. B
23. B
24. D
25. C
26. D
27. E
28. D
29. B
30. E
31. B
32. C
33. A
34. C
35. C
36. B
37. B
38. E
39. B
40. C
41. D
42. A
43. D
44. A
45. C
46. D
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