Download 1. The carbon atoms of cysteine are derived from: A. Methionine B

1.
The carbon atoms of cysteine are derived from:
A.
B.
C.
D.
E.
2.
LDL-receptor deficiency could cause all of the following to occur EXCEPT:
A.
B.
C.
D.
E.
3.
Ethanolamine phosphate + phosphatidic acid
CDP-ethanolamine + 1,2-diacylglycerol
CDP-phosphatidic acid + ehanolamine
UDP-ethanolamine + 1,2-diacylglycerol
Ethanolamine + ATP + 1,2-diacylglycerol
The second messenger system in cells involving the phosphatidyl inositol mechanism
initially results in an increase in cytosolic concentration of
A.
B.
C.
D.
E.
5.
A decrease in cellular uptake of LDL
Elevation of circulating LDL level
An increase in cholesterol synthesis in peripheral tissue
Inhibition of chylomicron synthesis
Elevated concentration of plasma cholesterol
The most direct route to phosphatidylethanolamine biosynthesis is:
A.
B.
C.
D.
E.
4.
Methionine
Serine
Homocysteine
Pyruvate
Tetrahydrobiopterin
Ca2+
Na+
cAMP
cGMP
K+
Biological lipid bilayer membranes contain which one of the following lipid compounds?
A.
B.
C.
D.
E.
Cholesterol.
Cholesteryl ester.
Linoleic acid.
Palmitic acid.
Stearic acid.
1
6.
Sterols that have 21 carbons include all of the following EXCEPT:
A.
B.
C.
D.
E.
7.
Acetate contains 2 carbon atoms and cholesterol contains 27. How many acetate
molecules are required to synthesize one molecule of cholesterol?
A.
B.
C.
D.
E.
8.
Tay-Sachs Disease
Gaucher's Disease
Hunter Syndrome
Nieman-Pick Disease
Fabry's Disease
All of the following statements concerning G proteins are correct EXCEPT:
A.
B.
C.
D.
E.
10.
15
16
17
18
19
All of the following diseases are due to a defect in lysosomal degradation of a
sphingolipid EXCEPT:
A.
B.
C.
D.
E.
9.
Estradiol
Progesterone
Cortisol
Pregnenolone
Aldosterone
They bind GTP
They are found on the outer surface of the plasma membrane,
One form activates phospholipase C.
One form inhibits adenylate cyclase
They have GTPase activity
The apolipoprotein that plays a role in the clearance of LDL from plasma is:
A.
B.
C.
D.
E.
Apolipoprotein A
Apolipoprotein B-100
Apolipoprotein B-48
Apolipoprotein C-II
Apolipoprotein E
2
11.
All of the following statements about phosphatidylserine are true EXCEPT:
A.
B.
C.
D.
12.
Which of the following statements concerning glutamine is FALSE:
A.
B.
C.
D.
E.
13.
Glutaminase generates glutamine from glutamate using free ammonia.
Glutamine is the most abundant amino acid in serum.
Guutamine synthetase utilizes ATP.
Glutamine donates a nitrogen to aspartate to form asparagine.
Glutamine can be used as a carbon source for energy by it conversion to TCA
cycle intermediates.
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.
B.
C.
D.
E.
14.
Can be converted to phosphatidylethanolamine by decarboxylation
Can be derived from phosphatidylethanolamine by reaction with ethanolamine
Is a major precursor to anionic glycerol-based phospholipids
Is an intermediate in a cycle that produces choline in a net fashion
The drug binds to Na+, K+-ATPase
The cytoplasmic Ca++ concentration increases
The cytoplasmic Na+ concentration increases
The cytoplasmic K+ concentration increases
The strength of cardiac muscle contraction increases
All of the following statements are true about the regulation of cholesterol biosynthesis
EXCEPT:
A.
B.
C.
D.
E.
Activation of a protease in the endoplasmic reticulum up regulates cholesterol
biosynthesis.
Statins reduce cholesterol biosynthesis by inhibiting HMG CoA reductase.
HMG CoA reductase is negatively regulated by glucagon through covalent
modification.
HMG CoA reductase levels are regulated by its degradation stimulated by sterol
derivatives.
The Sterol Regulatory Element Binding Protein only activates transcription of the
gene encoding HMG CoA reductase.
3
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.
B.
C.
D.
E.
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.
B.
C.
D.
E.
17.
acid hydrolases
clathrin
glucose-6-phosphate
mannose-6-phosphate
sialic acid
A ganglioside may contain all of the following EXCEPT:
A.
B.
C.
D.
E.
18.
Adenosine, cytosine, and uracil
Adenosine, guanine, and uracil
Adenosine, guanine, and thymidine
Cytosine, thymidine, and uracil
Guanine, thymidine, and uracil
A ceramide structure
Sulfate
One or more sialic acids
Glucose or galactose
A fatty acid
The formation of deoxyribonucleotides from the corresponding ribonucleotides:
A.
B.
C.
D.
E.
utilizes ribonucleoside monophosphates
requires an enzyme that utilizes tetrahydrofolic acid to reduce a disulfide bond
results in the deoxygenation of the sugar at the nucleoside diphosphate level
is carried out by phosphoribosyltransferases
is unimportant in the overall regulation of DNA systhesis
4
19.
Conjugation of bilirubin occurs in:
A.
B.
C.
D.
E.
20.
Which of the following statements regarding iron metabolism is FALSE:
A.
B.
C.
D.
E.
21.
Iron is transported in plasma chiefly bound to transferrin.
Reducing agents promote the absorption of iron from the intestine.
Iron crosses membranes in the Fe2+ form.
Iron is transported in plasma chiefly as part of ferritin.
Iron bound to ferritin is in the Fe3+ form.
All of the following statements about glycosaminoglycans and proteoglycans are true
EXCEPT:
A.
B.
C.
D.
E.
22.
the small intestine
the reticuloendothelial system
the liver
red blood cells
the plasma
The proteoglycans contain long, heteropolysaccharides consisting of a repeating
disaccharide unit that is covalently attached to protein.
Hyaluronic acid and aggrecan form a non-covalent complex held together by a
link protein.
Proteoglycans are synthesized on the plasma membrane.
Formation of iduronic acid occurs after addition of glucuronic acid to the growing
polysaccharide chain.
Sulfate is added to the growing heteropolysaccharide chain of proteoglycans.
Homocystinuria can result from all of the following EXCEPT:
A.
B.
C.
D.
E.
vitamin B12 deficiency
phenylalanine hydroxylase deficiency
folate deficiency
cystathionine synthetase deficiency
cystathionase deficiency
5
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.
B.
C.
D.
E.
26.
Which one of the following changes would you expect in a patient with a deficiency in
ApoC-II.
A.
B.
C.
D.
E.
27.
EGF receptors
Phospholipase C
ß-adrenergic receptors
Glucocorticoid receptors
Protein kinase A
Elevation of both serum HDL and LDL
Elevation of serum LDL only
Elevation of serum HDL only
Elevation of both serum chylomicrons and VLDL
Elevation of serum chylomicrons only
Which of the following reactions uses a tetrahydrofolate derivative rather than Sadenosylmethionine as a methyl donor:
A.
B.
C.
D.
E.
The methylation of guanidinoacetic acid to form creatine
The methylation of homocysteine to form methionine
The methylation of norcpinephrine to form epinephrine
The methylation of melatonin to form N-acetylserotonin
The methylation of phosphatidylethanolamine to form phosphatidylcholine
6
28.
The action of which of the following water-soluble vitamins is antagonized by
methotrexate?
A.
B.
C.
D.
E.
29.
All of the following statements are true about leukotrienes EXCEPT:
A.
B.
C.
D.
E.
30.
Growth hormone.
Insulin.
Epinephrine.
Thyroxine.
Glucagon.
The least oxidized form of carbon carried by tetrahydrofolic acid is:
A.
B.
C.
D.
E.
32.
They are derived from arachidonic acid.
They can be derivatized with amino acids.
Their synthesis is inhibited by aspirin.
Their precursor availability requires action by phospholipase A2.
Their synthesis is inhibited by anti-inflammatory steroids.
Steroid receptors are most closely related to receptors for which hormone?
A.
B.
C.
D.
E.
31.
Vitamin C
Vitamin B12
Vitamin B6 (pyridoxine)
Riboflavin
Folic acid
5,10-methylene
5,10-methenyl
5-formyl
5-methyl
10-formyl
All of the following processes occur rapidly in the membrane lipid bilayer EXCEPT:
A.
B.
C.
D.
E.
Flexing of the phospholipids fatty acyl chains
Lateral diffusion of phospholipids
Transverse diffusion of phospholipids
Rotation of phospholipids around their long axes
Lateral diffusion of membrane proteins
7
33.
The regulated step in heme biosynthesis is the step catalyzed by:
A.
B.
C.
D.
E.
34.
All of the following statements about O-linked glycoproteins are true EXCEPT:
A.
B.
C.
D.
35.
ferrochelatase
uroporphyrinogen III cosynthase
δ-aminolevulinic acid dehydratase
porphobilinogen deaminase
δ -aminolevulinic acid synthase
The carbohydrate component can be branched and can contain many different
monosaccharides.
The carbohydrate is attached to the protein through a leader sequence common to
all O-linked glycoproteins.
Activated sugars are added directly to serine and the growing polysaccharide
chain only in the Golgi.
Degradation of both the protein and polysaccharide components occurs in the
lysosomes.
Which of the following are true descriptions of glycosyl groups of membranes?
1.
2.
3.
4.
A.
B.
C.
D.
E.
36.
Associated with lipids.
Associated with proteins.
Localized on the extracellular side of plasma membranes.
Responsible for many antigenic determinants of the membrane.
1, 2 and 3
1 and 3
2 and 4
4 only
All four
Aside from obvious structural differences, pyrimidine synthesis differs from that of
purine synthesis in which way?
A.
B.
C.
D.
E.
Purine nucleotides are preformed prior to addition the ribose sugar
Purine synthesis does not require carbons carried by tetrahydrofolate
Purine synthesis requires carbamoyl phosphate
Pyrimidine nucleotides are built upon PRPP
Pyrimidine biosynthesis requires carbamoyl phosphate
8
37.
Allopurinol is used to treat gout because:
A.
B.
C.
D.
E.
38.
it activates thymidylate synthase
it inhibits PRPP synthesis
it inhibits hypoxanthine-guanine phosphoribosyltransferase
it inhibits xanthine oxidase
it activates phosphoribosyltransferases
All of the following are either primary or secondary active transporters EXCEPT:
A.
B.
C.
D.
E.
The iodide transporter of the thyroid follicular cell
The transporter that concentrates Ca++ in the sarcoplasmic reticulum
The red blood cell glucose transporter
The Na+/glucose symporter of intestinal epithelial cells
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.
B.
C.
D.
Vitamin A.
Vitamin D3.
Vitamin E.
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.
B.
C.
D.
E.
Glucosylceramide
Sphingosine
Prostacyclin
Cardiolipin
Estradiol
9
43.
All of the following are true of nitric oxide EXCEPT:
A.
B.
C.
D.
E.
44.
All of the following statements about N-linked glycoproteins are true EXCEPT:
A.
B.
C.
D.
E.
45.
Nucleotide-activated sugars required for synthesis of the carbohydrate component
are synthesized in the lumen of the Golgi and endoplasmic reticulum.
Synthesis of the carbohydrate component occurs in both the endoplasmic
reticulum and the Golgi.
The synthesis of the common oligosaccharide requires dolichol phosphate and
takes place associated with the endoplasmic reticulum membrane.
The carbohydrate component contains a common oligosaccharide made up of
mannose and N-acetyl glucosamine (GIcNAc).
During degradation in the lysosomes the polysaccharide chain must first be
separated from the protein before it can be completely hydrolyzed.
Oxaloacetate can be produced from which of the following amino acids?
A.
B.
C.
D.
E.
46.
it is made from nitrogen donated by citrulline
it activates guanylate cyclase
it is a gaseous signaling molecule
it can be made by a reaction carried out by nitric oxide syntheses
it is a potent vasodilator
Glutamate
Phenylalanine
Proline
Aspartate
Serine
All of the following statements concerning insulin's mechanism of action are TRUE
EXCEPT:
A.
B.
C.
D.
E.
Insulin binding to its receptor activates phosphorylation of its tyrosine residues.
Insulin receptor activation stimulates steps leading to an increased guanine
nucleotide exchange on RAS.
Insulin stimulates processes leading to MAP kinase activation.
The insulin-receptor complex is internalized by a clathrin-dependent process.
Insulin action involves participation of a trimeric G protein.
10
47.
The principle plasma carrier of endogenously synthesized triacylglycerol is:
A.
B.
C.
D.
E.
48.
Which of the following vitamins is required for the action of transaminases?
A.
B.
C.
D.
E.
49.
Serum albumin
LDL
HDL
Chylomicron
VLDL
Niacin
Pantothenate
Pyridoxal phosphate
Riboflavin
Thiamine
In de novo synthesis of cholesterol by the liver all of the following are true EXCEPT:
A.
B.
C.
D.
The precursor HMG-CoA is synthesized in the mitochondria
Synthesis involves the action of mixed function oxidases.
Mevalonic acid is a key intermediate.
The primary control site is the HMG-CoA reductase of the endoplasmic
reticulum.
11
BIOCHEMISTRY 2002
EXAM III
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
B
D
B
A
A
A
D
C
B
B
B
A
D
E
C
D
B
C
C
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
D
C
B
A
C
B
D
B
E
C
D
D
C
E
B
E
E
D
C
D
12
40
41
42
43
44
45
46
47
48
49
A
C
D
A
A
D
E
E
C
A