1.Pantothenic acid is a constituent of the coenzyme primarily involved in:
A. Decarboxylation
B. Acylation
C.Dehydrogenation
D.Reduction
E. Oxidation
2. One product from the hydrolytic activity of a phospholipase A2 is:
A. Monoacylglycerol
B. Diacylglycerol
C. Phosphatidylcholine
D. Lysophosphatidylcholine
E. Phosphatidic acid
3. The enzyme that transfers the methyl group from N5-methyltetrahydrofolate to
homocysteine contains which of the following?
A. Lipoic acid
B. Nicotinic acid
C. Pyridoxal phosphate
D. Thiamine pyrophosphate
E. Vitamin B12
4. A person with elevated plasma concentrations of lactate, pyruvate, propionate, and 3-
hydroxyisovalerate is a 1ike1v candidate for treatment with:
A. Biotin
R. Niacin
C. Pantothenate
D. Pyridoxine
E.Thiamine
5. All of the following statement about O-linked glycoproteins are true EXCEPT:
A.The carbohydrate component can be branched and can contain many different
monosaccharides
B. The linkage between carbohydrate and protein can be through either sent or
threonine
C. Activated sugars are added directly to serine or the growing polysaccharide chain
in the endoplasmic reticulum.
D.Degradation of both the protein and polysaccharide components occurs in the
lysosomes
6. The methyl group which is added to norepinephrine in the synthesis of epinephrine is
derived from which compound?
A. S-adenosylmethionine
B. Acetyl CoA
C. Tetrahydrofolic acid
D.Threonine
E. Serine
7. With regard to facilitated diffusion, which one of the following statements is TRUE?
A.Transport through the membrane is an equilibration process
B.The transporter can move solute in only one direction
C. ATP is required as an energy source
D. Very few solutes enter the cell by this mechanism
E.Solutes can only leave the cell by this process, not enter the cell
8.In de novo synthesis of cholesterol by the liver all of the following are true EXCEPT:
A. Mevalonic acid is a key intermediate
B. All of the carbons are originally supplied by acetyl-CoA
C. A mixed-function oxygenase (cytochrome P450) participates in only one reaction
in the process
D. The primary control site is at the level of HMG-CoA reductase
E. Proteases control expression and degradation of key enzymes in the process.
9. Severe phenylketonuria and shortened life span is most likely to result from
A.Excess dietary phenylalanine
B. Excess dietary tyrosine
C. Deficient or missing dihydroptetidine reductase
D. Deficiency in tetrahydrofolate
E. Deficiency in Vitamin B12
10. All of the following statements about phosphatidic-acidare true EXCEPT:
A.It is synthesized front fatty acyl CoA and glycerol 3-phosphate
B. It is a major precursor of sphingolipids
C. It is a major precursor to all glycerol-based phospholipids
D.It can give rise to diacylglycerol and ultimately triacylglycerol
E.It is one product of the catalytic action of phospholipasc D
11. Cholera toxin causes massive and often fatal diarrhea by:
A. Inactivating Gi protein
B.Irreversibly activating adenylate cyclase
C. Locking d, protein into an inactive form
D. Rapidly hydrolyzing G protein GTP to GDP
F. Preventing GTP from interacting with G protein
12. The most direct route to phos (lecitlbi. ) biosynthesis is:
A. Choline phosphate + phosphatidic acid
B.CDP-choline + 1,2-diacylglycerol
C. CDP-phosphatidic acid + choline
D.DDP-choline + 1,2-diacylglycerol
E. Choline + ATP + 1,2-diacylglycerol
13. Nitric oxide is a free radical that functions in a variety of physiologic processes in nerve,muscle, and other cells. The action of nitric oxide is to directly activate;
A. Calcium/calmodulin stimulated protein kinase.
B.Guanylate cyclase
C. Protein kinase C
D. Protein phosphatase-1
E. The nicotinic cholinergic receptor
14. The transmembrane domains of integral membrane proteins are most often composed of:
A. Hydrophobic amino acids in random coil conformation and with minimal lipid-
protein interaction
B. Hydrophilic amino acids in a conformation that minimizes lipid-protein
interaction
C. Hydrophobic amino acids in a helical conformation
D. Hydrophilic amino acids in a helical conformation
E. Amino acids carrying N- and O-linked polysaccharides
Match the vitamins below with the roles of these vitamins described in the items below (Questions 16 and 17):
A.Vitamin A
B. Vitamin C
C Vitamin D3
D.Vitamin E
E. Vitamin K
15. This vitamin is involved in conversion of prothrombin precursors during blood clotting.
16.This vitamin is an antioxidant that minimizes free radical oxidation of polyunsaturated
fatty acids in LDLs.
17..Which of the fol towing amino acids is a required component of the human diet?
A. Alanine
B.Glycine
C. Isoleucine
D. Serine
E.Tyrosine
18. 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 (GleNAc)
B.Synthesis of the carbohydrate component of secreted glycoproteins occurs in both
the endoplasmic reticutum and the Golgi.
C.The synthesis of the common oligosaccharide requires dolichol phosphate and
takes place associated with the endoplasmic reticulum membrane,
D. Nucleotide activated sugars required for synthesis of the carbohydrate component
are synthesized in the lumen of the Golgi and end
E. During degradation in the lysosomes the polysaccharide chain must first be
separated from the protein before it can be completely hydrolyzed.
19. Which statement best characterizes the difference between active mediated transport
(AMT) and passive mediated transport (PMT)?
A.Only PMT requires energy input
B.Only AMT can occur against a concentration gradient
C. Only AMT shows saturation kinetics
D.Only PMT shows specificity for solute transport
E. Only AMT can be inhibited
20.Which of the following compounds is common to the synthesis of Prostaglandins and
leukotrienes:
A. Glutathione
B- Prostaglandin H2
C- Arachidonic acid
D.Thromboxane
F. Prostacyclin
21.Acute intermittent porphyria is accompanied by an increased urinary level of:
A. Biliverdin
B. Conjugated bilirubin
C.Heme
D.Unconjugated bilirubin
E.Porphobilinogen
22. Homocystinuria results from a:
A.Phenylalanine hydroxylase deficiency
B. Renal defect
C.Cystathionine synthetase deficiency
D. Homogentisic acid oxidase deficiency
E.Methylmalonyl CoA mutase deficiency
23. The most active form ofvitamin D is the 1, 25-(OH)2D3 and it is obtained from:
A. Mucosal oxidation of dietary D3
B.Sunlight radiation of the skin
C.Liver hydroxylation of 25-(OH)D3
D.Kidney hydroxylation of 25-(OH)D3
24.In phospholipid synthesis, either phosphatidic acid or a phosphate covalently bound to a
water-soluble alcohol is activated by conjugation to:
A. AMP
B. CoA
C.Carnitine
U.UTP
E. CMP
25.The signal recognition particle receptor is found in which of the following subcellular
locations?
A.Endoplasmic reticulum
B. Mitochondrion
C. Nucleus
D. Plasma membrane
E. Ribosome
26. De novo pyrimidine synthesis requires:
A. Phosphoribosyl pyrophosphate (PRPP) for the initial step
B. Tetrahydrofblate for the incorporation of carbons 2 and 8
C. Both carbon and nitrogen of aspartate to form the ring
D. NH4+ as a substrate for carbamoyl phosphate synthetase II
E. Glycine as the source of two nitrogens in the ring
27. Generally steroid hormones:
A. Bind with intracellular receptors
B. Do not bind with any receptor
C.Activate adenylate cyclase
D.Stimulate the production of cyclic AMP
E. Require a G-protein transducer
28. All of the following statements about glycosaminoglycans and proteoglycans are true
EXCEPT:
A. The carbohydrate component of proteoglycans is a long, heteropolysaccharide
consisting of a repealing disaccharide unit.
B. The carbohydrate component of hyaluronic acid and aggrecan is synthesized in
the Golgi.
C. Proteoglycans contain over 90% carbohydrate
D. Formation of iduronic acid occurs after addition of glucuronic acid to the growing
polysaccharide chain,
E.Synthesis of proteoglycans involves the sequential addition of nucleotide
activated sugars to a protein-bound polysaccharide chain.
29. Receptors that are coupled to G-proteinsare defined by a strut includes:
A. Cysteine-rich extracellular domains
B. Seven transmembrane spanning dornains
C.Immunoglobulin-like extracellular domains
D.Homodimers
E.A domain for binding lipophilic hormones
30. A patient with a partial gastrectomy can develop a vitamin B12 deficiency due to a
decreased production of which of the following substances?
A. Elongation factor
B. Extrinsic factor
C. Factor V III
D. Intrinsic factor
E. Release factor
31. Which one of the following species would you expect to be elevated in serum from a
patient with decreased I id i arc activity
A. HDL and LDL
B.LDL only
C. HDL only
D.Both chylomicrons and VLDL
E. Chylomicrons only
32. Molecular iron Fe, is:
A. Stored primarily in the spleen
B. Excreted in the urine as Fe++
C. Stored in the body in combination with ferritin
D. Absorbed in the intestine by transferrin
E. Absorbed in the ferric, Fe+3 form
33.A ganglioside may contain all of the following EXCEPT:
A.A ceramide structureV
B.Phosphate
C. One or more sialic acids
D.Glucose or galactose
E. Nitrogen and oxygen atoms derived from serine
34.The ion that is most important for the transport of both water and nutrients from the
intestinallumen to the mucosal cell is:
A. Potassium
B.Sodium
C.Chloride
D. Bicarbonate
E.Magnesium
35.Folate is important in normal cellular development, and a deficiency of folate during
pregnancy can lead to neural tube defects. One known biochemical role of folate in
metabolism is to:
A.Function in one-carbon transfer reactions
B. Mediate decarboxylation reactions
C. Participate in transamination reactions
D.Serve as an antioxidant
E.Act as a neurotransmitter
36. Which of the following process is believed to have an important role in regulating the
rate of biosynthesis of cholesterol acetyl-CoA in the liver:
A. The condensation of malonyl-CoA with acetyl-CoA
B. The cleavage of HMG-CoA to form acetoacetate and acetyl-CoA
C. The reactions involved in the cyclization of the polyisoprenoid precursor of the
sterol ring system
D.The enzymatic reduction of 3-hydroxy-3-methylglutaryl-CoA
EThe introduction of a hydroxyl group at the 3-position of the steroid ring system
37.All of the following compounds have 21 carbons EXCEPT:
A. Testosterone
B. Progesterone
C. Cortisol
D. Pregnenolone
38.The rate of simple diffusion of a solute across a cell membrane:
A. Exhibits saturation kinetics
B.Is dependent an temperature
C.Is primarily against the concentration gradient
D. Is independent of membrane thickness
E.Is independent of solute concentration
39. The mainmetabolic source ofone-carbon units that are transferred by tetrahydrofolic
acid in humans is:
A.Alpha-carbon of glycine.
B.Beta-carbon of alanine
C. Beta-carbon of serine
D. CO2
E. Methionine
40.Hormonal stimulation of the formation of the second messenger inositol 1,4,5
triphosphate (IP3) directly leads to the release of which other intracellular messenger
A. Cyclic AMP
B.Prostaglandin
C. Calcium
D.Leukotriene
E. Thromboxane
41.Hormone receptors that stimulate cyclic AMP production:
A. Are part of a complex of two proteins that transform the external signal into
internal cyclic AMP production...
B. Cause release of the catalytic subunit upon binding of the hormone
C. Are proteins distinct and separate from those that catalyze the production of cyclic
AMP.
D. Are the outer protruding portion of a single protein that acts as a receptor and an
enzyme that produces cyclic AMP.
E.Are not very specific and bind a number of different hormones.
42. LDL-receptor deficiency could cause all of the following to occur EXCEPT:
A decrease in cellular uptake of LDL
B.Elevation of circulating LDL level
C.Increased cholesterol synthesis in peripheral tissue
D.Inhibition of chylomicron synthesis
E.Elevated concentration of plasma cholesterol
43. Biological lipid bilayer membranes contain significant amounts of which of the following
lipids:
A. Cholesterol
B.Cholesterol ester
C. Linoleate
D. Sphingosine
E. Triacylglycerol
44. It has been proposed that a factor in the pathogenesis of gout is a deficiency of renal
ammonium ion production leading to an acidic urine, a common sign in gout. Thus, the
substrate used for ammonium ion production in the kidney would be spared, and this
substance could he used instead for increased purine synthesis. This substrate is:
A.5-Phosphoribosylamine
B. Glycine
C.Uric acid
D. Aspartic acid
E. Glutamine
45, The first semester is almost over and you look forward to celebrating it with a nice cool
brew. Given that your beer of choice has the following composition, how many Calories
(i.e., kcal) does each 12-ounce bottle contain?
Alcohol = 14 g/12 oz.; Carbohydrate = 13 g/12 oz.; Protein = 1 g/12 oz.
A. 56
B.112
C. 154
D. 182
E. 196
46. The apoliproprotein that plays a major role in the clearance of triacylglycerol from VLDL is:
A.Apoliproprotein A
B.Apolipoprotcin B-100
C.Apolipoprotcin B-48
D. Apolipoprotein C
E. Apolipoprotcin E
Exam III Key Page 1 of 1
MedicalSchool Biochemistry
Keys to Exam III
Question / Answer / Question / AnswerVer 1 / Ver 2 / Ver 1 / Ver 2
1 / D / B / 25 / E / A
2 / C / D / 26 / D / C
3 / E / E / 27 / C / A
4 / A / A / 28 / E / B
5 / D / C / 29 / C / B
6 / C / A / 30 / B / D
7 / C / A / 31 / D / D
8 / E / C / 32 / C / C
9 / C / C / 33 / D / B
10 / C / B / 34 / A,B,C,D,E, / B
11 / B / B / 35 / C / A
12 / A / B / 36 / B / D
13 / D / B / 37 / B / A
14 / A / C / 38 / B / B
15 / B / E / 39 / B / C
16 / A,C / D / 40 / C / C
17 / C / C / 41 / A / C
18 / D / D / 42 / C / D
19 / D / B / 43 / A / A
20 / B / C / 44 / E / E
21 / B / E / 45 / D / C
22 / A / C / 46 / B / D
23 / C / D
24 / A / E
1