1. the Carbon Atoms of Cysteine Are Derived From

1. The carbon atoms of cysteine are derived from:

A. Methionine

B. Serine

C. Homocysteine

D. Pyruvate

E. Tetrahydrobiopterin

2. LDL-receptor deficiency could cause all of the following to occur EXCEPT:

A. A decrease in cellular uptake of LDL

B. Elevation of circulating LDL level

C. An increase in cholesterol synthesis in peripheral tissue

D. Inhibition of chylomicron synthesis

E. Elevated concentration of plasma cholesterol

3. The most direct route to phosphatidylethanolamine biosynthesis is:

A. Ethanolamine phosphate + phosphatidic acid

B. CDP-ethanolamine + 1,2-diacylglycerol

C. CDP-phosphatidic acid + ehanolamine

D. UDP-ethanolamine + 1,2-diacylglycerol

E. Ethanolamine + ATP + 1,2-diacylglycerol

4. The second messenger system in cells involving the phosphatidyl inositol mechanism

initially results in an increase in cytosolic concentration of

A. Ca2+

B. Na+

C. cAMP

D.cGMP

E. K+

5. Biological lipid bilayer membranes contain which one of the following lipid compounds?

A. Cholesterol.

B. Cholesteryl ester.

C. Linoleic acid.

D. Palmitic acid.

E. Stearic acid.

6. Sterols that have 21 carbons include all of the following EXCEPT:

A. Estradiol

B. Progesterone

C. Cortisol

D. Pregnenolone

E. Aldosterone

7. Acetate contains 2 carbon atoms and cholesterol contains 27. How many acetate

molecules are required to synthesize one molecule of cholesterol?

A. 15

B. 16

C. 17

D. 18

E. 19

8. All of the following diseases are due to a defect in lysosomal degradation of a

sphingolipid EXCEPT:

A. Tay-Sachs Disease

B. Gaucher's Disease

C. Hunter Syndrome

D. Nieman-Pick Disease

E. Fabry's Disease

9. All of the following statements concerning G proteins are correct EXCEPT:

A. They bind GTP

B. They are found on the outer surface of the plasma membrane,

C. One form activates phospholipase C.

D. One form inhibits adenylate cyclase

E. They have GTPase activity

10. The apolipoprotein that plays a role in the clearance of LDL from plasma is:

A. Apolipoprotein A

B. Apolipoprotein B-100

C. Apolipoprotein B-48

D. Apolipoprotein C-II

E. Apolipoprotein E

11. All of the following statements about phosphatidylserine are true EXCEPT:

A. Can be converted to phosphatidylethanolamine by decarboxylation

B. Can be derived from phosphatidylethanolamine by reaction with ethanolamine

C.Is a major precursor to anionic glycerol-based phospholipids

D. Is an intermediate in a cycle that produces choline in a net fashion

12. Which of the following statements concerning glutamine is FALSE:

A. Glutaminase generates glutamine from glutamate using free ammonia.

B. Glutamine is the most abundant amino acid in serum.

C. Guutamine synthetase utilizes ATP.

D. Glutamine donates a nitrogen to aspartate to form asparagine.

E. Glutamine can be used as a carbon source for energy by it conversion to TCA

cycle intermediates.

13. A patient is treated with a new cardiotonic steroid that acts similarly to ouabain. All of

the following would be expected to occur in the cardiac muscle cells upon treatment

EXCEPT:

A. The drug binds to Na+, K+-ATPase

B. The cytoplasmic Ca++ concentration increases

C. The cytoplasmic Na+ concentration increases

D. The cytoplasmic K+ concentration increases

E.The strength of cardiac muscle contraction increases

14. All of the following statements are true about the regulation of cholesterol biosynthesis

EXCEPT:

A. Activation of a protease in the endoplasmic reticulum up regulates cholesterol

biosynthesis.

B. Statins reduce cholesterol biosynthesis by inhibiting HMG CoA reductase.

C. HMG CoA reductase is negatively regulated by glucagon through covalent

modification.

D. HMG CoA reductase levels are regulated by its degradation stimulated by sterol

derivatives.

E. The Sterol Regulatory Element Binding Protein only activates transcription of the

gene encoding HMG CoA reductase.

15. Folate plays a role in single-carbon unit transfer in the synthesis of nucleotides. Which of

the following nucleotides require folate for synthesis?

A. Adenosine, cytosine, and uracil

B. Adenosine, guanine, and uracil

C. Adenosine, guanine, and thymidine

D. Cytosine, thymidine, and uracil

E. Guanine, thymidine, and uracil

16.A rapid way to purify proteins that are targeted to lysosomes would be to use affinity

chromatography. An appropriate antibody to use on an affinity chromatography column

to isolate these proteins would be one directed against:

A. acid hydrolases

B.clathrin

C.glucose-6-phosphate

D. mannose-6-phosphate

E. sialic acid

17. A ganglioside may contain all of the following EXCEPT:

A. A ceramide structure

B. Sulfate

C. One or more sialic acids

D. Glucose or galactose

E. A fatty acid

18. The formation of deoxyribonucleotides from the corresponding ribonucleotides:

A. utilizes ribonucleoside monophosphates

B. requires an enzyme that utilizes tetrahydrofolic acid to reduce a disulfide bond

C. results in the deoxygenation of the sugar at the nucleoside diphosphate level

D. is carried out by phosphoribosyltransferases

E. is unimportant in the overall regulation of DNA systhesis

19. Conjugation of bilirubin occurs in:

A.the small intestine

B. the reticuloendothelial system

C.the liver

D. red blood cells

E.the plasma

20. Which of the following statements regarding iron metabolism is FALSE:

A. Iron is transported in plasma chiefly bound to transferrin.

B. Reducing agents promote the absorption of iron from the intestine.

C. Iron crosses membranes in the Fe2+ form.

D. Iron is transported in plasma chiefly as part of ferritin.

E. Iron bound to ferritin is in the Fe3+ form.

21. All of the following statements about glycosaminoglycans and proteoglycans are true EXCEPT:

A. The proteoglycans contain long, heteropolysaccharides consisting of a repeating

disaccharide unit that is covalently attached to protein.

B. Hyaluronic acid and aggrecan form a non-covalent complex held together by a

link protein.

C.Proteoglycans are synthesized on the plasma membrane.

D. Formation of iduronic acid occurs after addition of glucuronic acid to the growing

polysaccharide chain.

E.Sulfate is added to the growing heteropolysaccharide chain of proteoglycans.

22. Homocystinuria can result from all of the following EXCEPT:

A. vitamin B12 deficiency

B. phenylalanine hydroxylase deficiency

C. folate deficiency

D. cystathionine synthetase deficiency

E. cystathionase deficiency

Match the following numbered statements and protein names to the lettered protein

classifications or descriptive statements of function in signal transduction.

23. Possesses tyrosine kinase activity.

24. Coupled to cAMP production via a specific G-protein.

25. Hydrolyzes PIP2, yielding DAG and 1P3-.

A. EGF receptors

B. Phospholipase C

C. ß-adrenergic receptors

D. Glucocorticoid receptors

E. Protein kinase A

26. Which one of the following changes would you expect in a patient with a deficiency in

ApoC-II.

A. Elevation of both serum HDL and LDL

B. Elevation of serum LDL only

C. Elevation of serum HDL only

D. Elevation of both serum chylomicrons and VLDL

E. Elevation of serum chylomicrons only

27. Which of the following reactions uses a tetrahydrofolate derivative rather than S-

adenosylmethionine as a methyl donor:

A. The methylation of guanidinoacetic acid to form creatine

B. The methylation of homocysteine to form methionine

C. The methylation of norcpinephrine to form epinephrine

D. The methylation of melatonin to form N-acetylserotonin

E. The methylation of phosphatidylethanolamine to form phosphatidylcholine

28. The action of which of the following water-soluble vitamins is antagonized by

methotrexate?

A. Vitamin C

B. Vitamin B12

C. Vitamin B6 (pyridoxine)

D. Riboflavin

E. Folic acid

29. All of the following statements are true about leukotrienes EXCEPT:

A. They are derived from arachidonic acid.

B. They can be derivatized with amino acids.

C. Their synthesis is inhibited by aspirin.

D. Their precursor availability requires action by phospholipase A2.

E. Their synthesis is inhibited by anti-inflammatory steroids.

30. Steroid receptors are most closely related to receptors for which hormone?

A. Growth hormone.

B. Insulin.

C. Epinephrine.

D. Thyroxine.

E. Glucagon.

31. The least oxidized form of carbon carried by tetrahydrofolic acid is:

A. 5,10-methylene

B.5,10-methenyl

C. 5-formyl

D. 5-methyl

E. 10-formyl

32. All of the following processes occur rapidly in the membrane lipid bilayer EXCEPT:

A. Flexing of the phospholipids fatty acyl chains

B. Lateral diffusion of phospholipids

C. Transverse diffusion of phospholipids

D. Rotation of phospholipids around their long axes

E. Lateral diffusion of membrane proteins

33. The regulated step in heme biosynthesis is the step catalyzed by:

A. ferrochelatase

B. uroporphyrinogen III cosynthase

C. δ-aminolevulinic acid dehydratase

D. porphobilinogen deaminase

E. δ -aminolevulinic acid synthase

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 to the protein through a leader sequence common to

all O-linked glycoproteins.

C. Activated sugars are added directly to serine and the growing polysaccharide

chain only in the Golgi.

D. Degradation of both the protein and polysaccharide components occurs in the

lysosomes.

35. Which of the following are true descriptions of glycosyl groups of membranes?

1. Associated with lipids.

2.Associated with proteins.

3. Localized on the extracellular side of plasma membranes.

4. Responsible for many antigenic determinants of the membrane.

A. 1,2and3

B. 1 and 3

C. 2 and 4

D. 4 only

E.All four

36. Aside from obvious structural differences, pyrimidine synthesis differs from that of

purine synthesis in which way?

A.Purine nucleotides are preformed prior to addition the ribose sugar

B. Purine synthesis does not require carbons carried by tetrahydrofolate

C. Purine synthesis requires carbamoyl phosphate

D. Pyrimidine nucleotides are built upon PRPP

E. Pyrimidine biosynthesis requires carbamoyl phosphate

37. Allopurinol is used to treat gout because:

A. it activates thymidylate synthase

B. it inhibits PRPP synthesis

C. it inhibits hypoxanthine-guanine phosphoribosyltransferase

D. it inhibits xanthine oxidase

E. it activates phosphoribosyltransferases

38. All of the following are either primary or secondary active transporters EXCEPT:

A. The iodide transporter of the thyroid follicular cell

B. The transporter that concentrates Ca++ in the sarcoplasmic reticulum

C. The red blood cell glucose transporter

D. The Na+/glucose symporter of intestinal epithelial cells

E. The Na +/Ca++ antiporter of the plasma membrane of cardiac muscle

Match the fat-soluble vitamins below with the roles of these vitamins described in the items

below:

A. Vitamin A.

B.Vitamin D3.

C. Vitamin E.

D. Vitamin K.

39. This vitamin is involved in conversion of prothrombin precursors during blood clotting.

40. This vitamin combines with opsin to form the visual pigment in ocular photoreceptors.

41. This vitamin is an antioxidant which minimizes oxidation of polyunsaturated fatty acids

by free radicals.

42. Which of the following contains glycerol:

A. Glucosylceramide

B. Sphingosine

C.Prostacyclin

D. Cardiolipin

E. Estradiol

43. All of the following are true of nitric oxide EXCEPT:

A. it is made from nitrogen donated by citrulline

B. it activates guanylate cyclase

C. it is a gaseous signaling molecule

D. it can be made by a reaction carried out by nitric oxide syntheses

E. it is a potent vasodilator

44.All of the following statements about N-linked glycoproteins are true EXCEPT:

A. Nucleotide-activated sugars required for synthesis of the carbohydrate component

are synthesized in the lumen of the Golgi and endoplasmic reticulum.

B. Synthesis of the carbohydrate component occurs in both the endoplasmic

reticulum and the Golgi.

C. The synthesis of the common oligosaccharide requires dolichol phosphate and

takes place associated with the endoplasmic reticulum membrane.

D. The carbohydrate component contains a common oligosaccharide made up of

mannose and N-acetyl glucosamine (GIcNAc).

E. During degradation in the lysosomes the polysaccharide chain must first be

separated from the protein before it can be completely hydrolyzed.

45.Oxaloacetate can be produced from which of the following amino acids?

A. Glutamate

B. Phenylalanine

C. Proline

D.Aspartate

E. Serine

46. All of the following statements concerning insulin's mechanism of action are TRUE

EXCEPT:

A. Insulin binding to its receptor activates phosphorylation of its tyrosine residues.

B.Insulin receptor activation stimulates steps leading to an increased guanine

nucleotide exchange on RAS.

C. Insulin stimulates processes leading to MAP kinase activation.

D. The insulin-receptor complex is internalized by a clathrin-dependent process.

E. Insulin action involves participation of a trimeric G protein.

47. The principle plasma carrier of endogenously synthesized triacylglycerol is:

A. Serum albumin

B.LDL

C. HDL

D. Chylomicron

E. VLDL

48. Which of the following vitamins is required for the action of transaminases?

A.Niacin

B. Pantothenate

C. Pyridoxal phosphate

D. Riboflavin

E. Thiamine

49. In de novo synthesis of cholesterol by the liver all of the following are true EXCEPT:

A. The precursor HMG-CoA is synthesized in the mitochondria

B. Synthesis involves the action of mixed function oxidases.

C. Mevalonic acid is a key intermediate.

D. The primary control site is the HMG-CoA reductase of the endoplasmic

reticulum.

BIOCHEMISTRY 2002

EXAM III

1