Download 1 - Medical Mastermind Community

1.
All of the following statements about O-linked glycoproteins are true EXCEPT:
A.
B.
C.
D.
E.
2.
Cystic fibrosis patients are frequently on antibiotics for infections. Antibiotics increase
the chances for deficiency in which one of the following vitamins?
A.
B.
C.
D.
E.
3.
Vitamin A
Vitamin C
Vitamin D
Vitamin E
Vitamin K
All of the following steps take place in insulin biosynthesis EXCEPT:
A.
B.
C.
D.
E.
4.
The carbohydrate component can be branched and can contain many different
monosaccharides.
The carbohydrate is attached directly to a growing oligosaccharide linked to the
protein through either scrine or threonine.
Activated sugars are added to protein only in the Golgi.
Degradation of both the protein and oligosaccharide components occurs in the
lysosomes.
The oligosaccharide component of all O-linked glycoproteins contains a common
leader sequence attached directly to the protein.
Insulin mRNA contains signal colons.
The A and B chains of insulin are held together by two interchain disulfide bonds.
Disulfide bond formation occurs in the cytosol.
Mature insulin is stored in secretory granules.
Release of insulin into the circulation is a highly regulated process involving
Ca2+-dependent exocytosis.
Ascorbic acid is associated with all of the following processes EXCEPT:
A.
B.
C.
D.
E.
Iron absorption from the intestine
Participation in hydroxylation reactions in the synthesis of collagen
Wound healing
Inactivation of oxygen free radicals in aqueous environments
Inactivation of lipid peroxides in membranes
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5.
All of the following statements about glycosaminoglycans and proteoglycans are true
EXCEPT:
A.
B.
C.
D.
E.
6.
Transport by simple diffusion is characterized by all of the following EXCEPT:
A.
B.
C.
D.
E.
7.
A ceramide structure
A fatty acid
One or more sialic acids
Glucose or galactose
All of the following can lead to hyperbilirubinemia EXCEPT:
A.
B.
C.
D.
E.
9.
Nonsaturablc increase as a function of concentration
Lacks stereospecificity
Increases as a function of lipid solubility
Can be abolished by a single mutation
Does not result in movement against a concentration gradient
A cerebroside may contain all of the following EXCEPT:
A.
B.
C.
D.
8.
Hyaluronic acid and aggrecan form a non-covalent complex held together by a
link protein.
Sulfate is added to the growing oligopolysaccharide chain of proteoglycans by
PAPS (3'-phosphoadenosine 5'-phosphosulfate).
Glycosaminoglycans are I00% polysaccharide while proteoglycans are composed
of mostly polysaccharide with a small amount of protein.
Formation of iduronic acid occurs after addition of glucuronic acid to the growing
oligosaccharide chain.
The glycosaminoglycan hyaluronic acid is assembled in the Golgi.
Elevations in uric acid
Liver Disease
Hemolytic crises
Blockage of the bile duct
Premature birth
Which of the following enzymes in the heme biosynthetic pathway is inhibited by lead?
A.
B.
C.
D.
E.
Protoporphyrinogen oxidase
Uroporphyrinogcn III cosynthase
δ-aminolevulinic acid dehydratase
Porphobilinogen deaminase
δ-aminolevulinic acid synthase
2
10.
The carbon atoms of aspartate are derived directly from:
A.
B.
C.
D.
E.
11.
All of the following statements about cholesterol in membranes are true EXCEPT:
A.
B.
C.
D.
E.
12.
Cholesterol increases the phase transition temperature of membranes containing
mostly unsaturated fatty acid side chains.
Cholesterol is more abundant in the plasma membrane than mitochondrial
membranes.
The cholesterol content of a membrane has no influence on the rate of ion
transport by a carrier-type ionophore.
Cholesterol is absent from bacterial membranes.
The hydroxyl group of cholesterol in membranes is in contact with the aqueous
phase.
All of the following statements concerning iron utilization in the body are true EXCEPT:
A.
B.
C.
D.
E.
13.
Methionine
Serine
Homocysteine
Oxaloacetate
Tetrahydrobiopterin
A clathrin-mediated process is involved in iron uptake into cells.
Ferrous (Fe2+) iron is transported in serum bound to transferrin.
Ferrous (Fe2+) iron is the form preferentially absorbed in the intestine.
Intracellular iron is stored in the liver as the ferric form (Fe3+) bound to ferritin.
Some iron is released into the intestine due to secretion in bile.
Binding of gonadotrophin-releasing hormone to its receptor in the anterior pituitary leads
to all of the following responses EXCEPT:
A.
B.
C.
D.
E.
Activation of a G protein
Activation of phospholipase C
Activation of protein kinase C
Decrease in cytosolic Ca2+
Release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
from the cell
3
14.
All of the following diseases are due to a defect in lysosomal degradation of a
sphingolipid EXCEPT:
A.
B.
C.
D.
E.
15.
Which of the following reactions uses S-adenosylmethionine as a direct methyl donor?
A.
B.
C.
D.
E.
16.
The conversion of methylmalonyl CoA to succinyl CoA
The methylation of dUMP to form dTMP
The methylation of homocysteine to form methionine
The formation of 5,10-methylene-FH4 from serine
The methylation of guanidinoacetate to form creatine
All of the following statements concerning vitamin D are correct EXCEPT:
A.
B.
C.
D.
E.
17.
Hurler
Gaucher's
Tay-Sachs
Nieman-Pick
Fabry's
In skin, 7-dehydrocholesterol is converted to cholcealciferol by the action of
mixed function oxidases.
In kidney, formation of calcitrol (active vitamin D) is stimulated by parathyroid
hormone.
Vitamin D inhibits renal excretion of Ca2+.
High levels of Ca2+ in the blood decrease formation of the active vitamin.
Vitamin D stimulates Ca2+ absorption in the intestine.
The protein that plays a role in the transfer of cholesterol from extrahepatic tissue to
HDLs is:
A.
B.
C.
D.
E.
Apolipoprotein A
Apolipoprotein B-100
Apolipoprotein B-48
Apolipoprotein C
Apolipoprotein E
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18.
Non-Steroidal Anti-Inflammatory Drugs (NSAID) reduce the cellular levels of all of the
following EXCEPT:
A.
B.
C.
D.
19.
Folate is reduced to tetrahydrofolic acid by a reaction catalyzed by the enzyme:
A.
B.
C.
D.
E.
20.
Dihydrofolate reductase
Methotrexate reductase
Thymidylate synthetase
Dihydropteridine reductase
Ribonucleotide reductase
With respect to bile acids/salts all of the following are true EXCEPT:
A.
B.
C.
D.
E.
21.
Prostacyclin
Prostaglandin H2 (PGH2)
Arachidonic acid
Thromboxane
Secondary refers to those bile acids/salts that are sulfated in the liver.
Primary refers to those bile acids/salts that are initially made in the liver.
The rate limiting step in their synthesis is stimulated by cholesterol.
Conjugation of bile salts with glycine or taurine increases their solubility in water.
Incomplete reabsorption of bile salts/acids is a mechanism for elimination of
cholesterol.
All of the following statements about phosphatidylserine are true EXCEPT:
A.
B.
C.
D.
It is a major precursor in sphingolipid biosynthesis.
It can be made by reaction of serine with phosphatidylcholine.
It can be converted to phosphatidylethanolamine by decarboxylation.
It is an intermediate in a cycle that produces ethanolamine in a net fashion.
22. Tyrosine can be produced from which of the following amino acids?
A.
B.
C.
D.
E.
Glutamate
Phenylalanine
Proline
Methionine
Serine
5
23.
Which of the following DOES NOT provide carbon(s) to the building of the purine ring
structure?
A.
B.
C.
D.
E.
24.
All of the following statements about steroid hormone receptors are true EXCEPT:
A.
B.
C.
D.
E.
25.
The receptor contains a DNA binding domain that binds zinc at specific sites.
The hormone-receptor complex binds to specific response elements in genes
leading to activation of transcription.
Receptors contain a tyrosine kinase that is activated by hormone binding.
The steroid hormone binds its receptor intracellularly.
Hormone binding to its receptor is saturable.
The signaling pathways triggered by epidermal growth factor and insulin share all of the
following characteristics in common EXCEPT:
A.
B.
C.
D.
E.
26.
Glycine
Methenyl-FH4
CO2
Formyl-FH4
Glutamine
Receptor activation results in autophosphorylation of intracellular tyrosine kinase
domains of the receptor.
Hormone-receptor complexes are internalized into the cell by clathrin-mediated
endocytosis.
Binding of hormone causes dimerization of the receptor.
Both hormones contain at least one intrachain disulfide bond.
Receptor activation leads to a cascade of intracellular phosphorylations.
The two enzymes that require vitamin B12 cofactors are:
A.
B.
C.
D.
E.
Methylmalonyl CoA mutase and mammalian ribonucleotide reductase.
Cystathionine synthase and mammalian ribonucleotide reductase.
Methylmalonyl CoA mutase and methionine synthase.
Mammalian ribonucleotide reductase and thymidylate synthase.
Cystathionine synthase and thymidylate synthase.
6
27.
All of the following statements concerning membrane transport processes are true
EXCEPT:
A.
B.
C.
D.
E.
28.
Which of the following is TRUE of both proteoglycans and glycoproteins?
A.
B.
C.
D.
29.
The saccharide component of both proteoglycans and glycoproteins can be
branched.
Polysaccharides of both glycoproteins and proteoglycans are made up of repeating
disaccharide units.
Polysaccharides of both proteoglycans and glycoproteins can contain sialic acid.
The protein component of both proteoglycans and glycoproteins is synthesized in
the endoplasmic reticulum.
VLDLs are synthesized in the liver for transport of which of the following to adipose
tissue:
A.
B.
C.
D.
E.
30.
The protein defective in cystic fibrosis is a chloride channel containing two ATP
binding domains.
Resistance to chemotherapy drugs in cancer cells can occur by gene amplification
of an endogenous ATP-dependent transporter.
Ca2+ transporters in the endoplasmic reticulum utilize ATP hydrolysis to maintain
cytosolic Ca2+ levels.
The plasma membrane Na+/K+-ATPase transports 3 Na out of the cell for every 2
K+ it transports into the cell.
Glucose uptake into red blood cells is a Na+-dependent process.
Triacylglycerols
LDL receptors
Apolipoproteins for HDL synthesis
Apolipoprotein B-100
Phospholipids
Which one of the following treatments would INCREASE secondary active transport of
glucose into kidney and intestinal epithelial cells?
A.
B.
C.
D.
E.
Addition of ouabain
Decrease intracellular K+ levels
Decrease intracellular Na+ levels
Addition of a glucose analog
Decrease in intracellular ATP levels
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31.
All of the following are involved in transfer of dietary triacylglycerol from the intestine
to the adipose EXCEPT:
A.
B.
C.
D.
E.
32.
Cellular energy generation is severely compromised in thiamine deficiency because
thiamine pyrophosphate is:
A.
B.
C.
D.
E.
33.
A major cofactor for most oxidation-reduction reactions
An essential cofactor for pyruvate and α-ketoglutarate dehydrogenases
A cofactor for amino acid decarboxylases
Necessary for utilizing amino acids for energy via transamination
Necessary for oxidation of alcohol
The most direct route to phosphatidylinositol biosynthesis is:
A.
B.
C.
D.
E.
34.
Chylomicrons
Apolipoprotein B-48
Lipoprotein lipase
Apolipoprotein C-II
Lecithin:Cholesterol Acyl Transferase
Inositol phosphate + phosphatidic acid
CDP-inositol + 1,2-diacylglycerol
CDP-diacylglycerol + inositol
Phosphatidyicholine + inositol
Inositol + ATP + 1,2-diacylglycerol
All of the following statements concerning lipids in membranes are true EXCEPT:
A.
B.
C.
D.
E.
In mammalian cells, cardiolipin is found predominantly in the mitochondrial
membrane.
Free fatty acids are largely absent from cell membranes.
Sphingomyelin is a major component of bacterial membranes.
An increase in chain length of fatty acyl residues of lipids makes the membrane
less fluid.
Carbohydrate-containing lipids are largely found in the plasma membrane of
mammalian cells.
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35.
Which one of the following changes would you expect in a patient with a deficiency in
the B-48:E receptor?
A.
B.
C.
D.
E.
36.
All of the following statements about the regulation of cholesterol biosynthesis are true
EXCEPT:
A.
B.
C.
D.
37.
HMG CoA reductase levels are regulated by a transcription activator released
from the Golgi by proteolysis.
Stating reduce cholesterol biosynthesis by inhibiting HMG CoA reductase.
HMG CoA reductase levels are reduced by its proteolysis stimulated by sterol
derivatives.
The Sterol Regulatory Element Binding Protein only activates transcription of the
gene encoding HMG CoA reductase.
Lesch-Nyhan Syndrome is associated with a deficiency in:
A.
B.
C.
D.
E.
38.
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 chylomicron remnants only
Adenosine deaminase
Hypoxanthine-guanine phosphoribosyltransferase
Orotate phosphoribosyltransferase
Orotidine decarboxylase
Adenine phosphoribosyltransferase
The carbons of glycine are used in the formation of
1.
2.
3.
4.
A.
B.
C.
D.
E.
Creatine
Heme
Adenosine monophosphate
Tyrosine
1, 2, 3 only
1, 3 only
2, 4 only
4 only
All of the above
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39.
Which of the following molecules is a product of pyrimidine degradation?
A.
B.
C.
D.
E.
40.
Which ONE of the following individuals would most likely be in nitrogen equilibrium?
A.
B.
C.
D.
E.
41.
A normal adult male
A normal pregnant female
A growing child
An adult male recovering from surgery
A normal female on a very low protein diet
In the biosynthesis of cell membrane proteins, each of the following steps occurs
EXCEPT:
A.
B.
C.
D.
E.
42.
ß-Aminoisobutyrate
Xanthine
Uric acid
Allopurinol
Orotate
Signal recognition particles binds to the signal codons of mRNA's encoding
membrane or secreted proteins.
Docking of ribosomes to the endoplasmic reticulum membrane involves a
GTP/GDP cycle.
Specialized proteins catalyze folding of the nascent polypeptide chains.
Chain elongation and translocation of the nascent polypeptide through a pore in
the endoplasmic reticulum membrane are separate but simultaneous processes.
Many mitochondrial proteins are encoded in the nucleus and are made in the
cytosol on free ribosomes.
Which of the following statements about serine is TRUE?
A.
B.
C.
D.
E.
It is converted to pyruvate and urea by a dehydratase.
It may be synthesized from glucose via an intermediate of the TCA cycle.
It is converted to glycine by a reaction requiring tetrahydrofolate.
It is the only amino acid that contains a hydroxyl group.
It is an essential amino acid.
10
43.
In de novo synthesis of cholesterol by the liver all of the following are true EXCEPT:
A.
B.
C.
D.
44.
All of the following statements about N-linked glycoproteins are true EXCEPT:
A.
B.
C.
D.
45.
Phosphatidylinositol
Sphingomyelin
Ceramide
Leukotriene C4
Prostacyclin
All of the following treatments will tend to increase intracellular cyclic AMP levels
EXCEPT:
A.
B.
C.
D.
E.
47.
The carbohydrate component contains a common oligosaccharide made up of
mannose and N-acetyl glucosamine (GIcNAc).
Formation of the oligosaccharide component occurs in both the endoplasmic
reticulum and the Golgi.
The elongation of the protein-linked oligosaccharide in the Golgi requires
dolichol phosphate.
Nucleotide-activated sugars required for synthesis of the oligosaccharide
component are synthesized in the cytoplasm.
Glycerol is present in which one of the following?
A.
B.
C.
D.
E.
46.
Farnesyl pyrophosphate is the immediate precursor to squalene.
All of the carbons are supplied by 18 acetyl-CoA's.
The precursor HMG-CoA is synthesized in the mitochondrial matrix.
Several reactions involve mixed function oxidases.
Addition of epinephrine
Addition of caffeine
Addition of cholera toxin
Addition of diptheria toxin
Inhibition of the intrinsic GTPase activity of a Gs protein
All of the following statements concerning G proteins involved in intracellular signaling
are true EXCEPT:
A.
B.
C.
D.
E.
Certain oncogenes result from mutations in a G protein.
Cholera toxin action is associated with covalent modification of a G protein.
All G proteins contain an intrinsic GTPase activity.
Pertussis toxin is associated with covalent modification of a G protein.
All G proteins are monomeric.
11
Medical School Biochemistry Course
EXAM ANSWER KEY
BLOCK III
Q#
1
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V1
V2
V3
V4
C
C
E
A
B
D
E
C
A
A
C
A
B
D
E
C
C
E
E
A
E
A
D
A
C
E
C
C
A
C
A
B
A
A
C
E
C
C
D
C
B
E
C
D
C
E
B
C
C
A
D
B
A
D
A
E
C
E
E
D
C
D
A
A
A
C
A
C
C
A
C
C
A
A
A
E
D
C
A
A
A
A
A
E
A
E
B
D
C
C
E
E
E
C
C
A
A
E
C
A
C
E
C
D
D
D
E
E
E
B
D
D
E
B
A
C
D
B
C
E
E
A
E
E
E
A
B
A
A
C
C
A
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B
C
B
E
C
E
C
E
C
D
C
C
D
B
A
D
C
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C
E
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A
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A
A
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E
C
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C
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E
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C
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A
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A
D
D
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D
E
E
A
E
C
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