Previous Biochem Exams 1-3 Flashcards
What is the most accurate combination of each lipoprotein lipase isomer with its Km, relative to each other?
adipose tissue has a larger Km than heart muscle which has a smaller Km
Which molecules will be fund in mixed micelles of the intestines following digestion of a typical meal?
cholesterol
What is true regarding lipid metabolism?
lipids are passively transported into intestinal cells for accumulation into chylomicrons
pancreatic juice is rich in a proenzyme form of phospholipase A2
phospholipase A2 can remove fatty acids from a phospholipid
What is false regarding lipid metabolism?
more than 25% of dietary cholesterol is in esterified form
- Which of the following statements regarding lipid metabolism is false?
A. chylomicrons are composed of material that includes phospholipids, esterified cholesterol and apolipoprotein B-100
B. the mixture of lipids absorbed by the intestinal cells migrate to the ER to be packaged into a lipoprotein
C. newly synthesized TAGs and cholesteryl esters are very hydrophobic and aggregate in an aqueous environment D. none of the above are false
A. chylomicrons are composed of material that includes phospholipids, esterified cholesterol and apolipoprotein B-100
- Which statement is correct?
A. HDLs may be synthesized in both the intestine and the liver
B. the major forces driving the formation of lipid bilayers are the hydrophobic interactions between the polar head groups
C. cellular membranes contain cholesterol esters
D. none of the above are correct
E. all the above are correct
A. HDLs may be synthesized in both the intestine and the liver
What tissue is primarily involved in the synthesis of chylomicrons?
small intestinal epithelium
Which enzyme initially hydrolyzes dietary triacylgycerides containing short chain immediately after ingestion?
gastric lipase
All fatty acids require assistance by mixed micelles for absorption by intestinal mucosa.
false
- The following statements regarding plasma lipoproteins metabolism are correct EXCEPT
A. all undergo Apo-B100-mediated endocytosis
B. usually have a nonpolar core containing triacylglycerols and cholesterol esters
C. do not generally contain free (unesterified) fatty acids
D. include chylomicrons generated
A. all undergo Apo-B100-mediated endocytosis
What is the closest percentage of cholesterol molecules that are deprotonated at physiological pH?
0.01%
What is the correct protein composition of lipoproteins in order from highest to lowest ratio of protein to lipid?
HDL > LDL > IDL > VLDL > chylomicron
Which of the following are NOT correct?
A. HMG CoA Reductase is the enzyme catalyzing the major control point for cholesterol biosynthesis
B. Lipid/cholesterol deposition can lead to plaque formation, causing the narrowing of blood vessels, atherosclerosis and increased risk of coronary artery disease
C. Cholesterol may be eliminated from the liver as esterified cholesterol in the bile, converted to bile salts that are secreted into the intestinal lumen or sent to the peripheral tissues
D. all of the above (a-c) are correct
E. none of the above (a-c) are correct
C. Cholesterol may be eliminated from the liver as esterified cholesterol in the bile, converted to bile salts that are secreted into the intestinal lumen or sent to the peripheral tissues
Which of the following are NOT correct?
A. Plasma lipoproteins do not generally contain free (unesterified) fatty acids
B. Statins are used to decrease plasma cholesterol in patients with hypercholesterolemia
C. More than 90% of the TAG in the core of circulating HDL is degraded by LPL
D. all of the above (a-c) are correct
E. none of the above (a-c) are correct
C. More than 90% of `the TAG in the core of circulating HDL is degraded by LPL
Which of the following are NOT correct?
A. The primary role of LDL particles is to provide cholesterol to the liver
B. Bile salts are highly effective detergents
C. Patients with cystic fibrosis have a defect in the function of the chloride channels
D. all of the above (a-c) are correct
E. none of the above (a-c) are correct
A. The primary role of LDL particles is to provide cholesterol to the liver
Which of the following are NOT correct?
A. Acetate provides half the carbons in the synthesis of cholesterol
B. Chylomicrons remnants, are removed from the circulation by the liver
C. HMG CoA reductase is inhibited by high cholesterol
D. all of the above (a-c) are correct
E. none of the above (a-c) are correct
A. Acetate provides half the carbons in the synthesis of cholesterol
Which enzyme hydrolyzes dietary triacylglycerides containing short chain fatty acids immediately after ingestion?
lingual lipase
A 45 year old person is found to have an elevated serum cholesterol of 300 mg percent measured by standard conditions after a 12 hour fast. Which lipoprotein would contribute to the measurement of plasma cholesterol in a normal person following a 12 hours fast
HDL and LDL
The following statements regarding lipoprotein metabolism are correct EXCEPT
A. VLDL contains cholesterol
B. VLDL contains TAGs
C. VLDL contains a protein called apolipoprotein B-100
D. cholesterol esters in the LDL are metabolized by LPL
cholesterol esters in the LDL are metabolized
The correct statements about chylomicron metabolism include:
A. chylomicrons are synthesized in the liver
B. chylomicrons are dense lipoprotein particles
C. chylomicron remnants are delivered into the intestine through receptor-mediated endocytosis
D. all of the above (a-c) are correct
E. none of the above (a-c) are correct
none of the above
What is the primary site of the synthesis of IDLs?
vascular endothelium
A patient with a history of recurring attacks of pancreatitis and increased plasma triglyceride levels associated with chylomicrons, most likely has deficiency in?
lipoprotein lipase
A patient presents with very high levels of serum cholesterol. After a series of tests, it is concluded that the patiet has high circulating levels of LDL cholesterol, but has normal levels of liver LDL. One potential explanation for this observation is?
a mutation in Apo B100
A patient with hereditary type I hyperlipidemia presents with elevated levels of chylomicrons and VLDL triglycerides in the blood. The main function of the chylomicron in circulation is to do?
transport dietary lipids from the intestine to target tissues
The modification to bile salts that increases with working pH range and amphipathic nature of bile salts is?
conjugation to taurine or glycine
What are the products of the action of lipoprotein lipase of TAGs?
glycerol and fatty acids
The molecule has no phosphates attached to the sugar that is attached to a purine. It is a…
nucleoside
5-phosphoribosyl-1-pyrophosphate (PRPP) is used in de novo synthesis of AMP but not in the salvage synthesis of AMP.
false
Inosine monophosphate (IMP) is the precursor for both AMP and GMP.
true
Mycophenolic acid inhibits an enzyme involved in the de novo synthesis of
GMP
Hypoxanthine-guianine phosphoribosyltransferase is involved in
salvage pathway
Capecitabine is a prodrug that undergoes enzymatic activation to inhibit
thymidylate synthase
Substrates for ribonucleotide reductase includes ADP, GDP, CDP, and TDP
false, not TDP
What is the least contribution to stabilize base stacking of DNA?
hydrogen bonding
What sequence is suitable for antiparallel triple helix formation with doublestranded DNA that consists of 5’-d(GAAGGGAAAA)-3’ and 3’-d(CTTCCCTTTT)-5’?
3’-d(GAAGGGAAAA)-5’
Inhibition of histone deacetylase induces the formation of a chromatin structure that is NOT suitable for gene transcription.
false
What is the biggest increase in its surface exposure during change from duplex DNA to a random coil?
base
Which of the following statements is FALSE?
(A) B-DNA is the most prevalent conformation for duplex DNA under physiological conditions.
(B) A-DNA is a right-handed helix.
(C) Z-DNA is a left-handed helix.
(D) In Z-DNA, purine adopts syn conformation.
(E) B-DNA has wide minor groove that is easily accessible to proteins.
(E) B-DNA has wide minor groove that is easily accessible to proteins.
To elongate DNA chain, DNA polymerases require a DNA template, 3’end (DNA or RNA primer), and NTP.
false
Which of the following statements about is FALSE?
(A) Pol I has 3’ to 5’ exonuclease activity.
(B) Pol I has 5’ to 3’ exonuclease activity.
(C) Pol III has 3’ to 5’ exonuclease activity.
(D) Pol III has 5’ to 3’ exonuclease activity.
(D) Pol III has 5’ to 3’ exonuclease activity.
Topotecan inhibits topoisomerase by forming a covalent bond with the enzyme.
false
The end replication by telomerase, primase, DNA polymerase, and ligase produces a 5’ end overhang with lengthened telomeres.
false
Replication of mitochondrial DNA does NOT require telomerase
true
Nucleobase 8-oxoguanine causes what mutation after rounds of DNA replication?
G to T transversion
Nucleobase lesion OMe-6-guanine causes what mutations after rounds of DNA replication
G to A transition
The Fenton reaction of ____ with Fe(II)-complexed DNA produces ____.
hydrogen peroxide
hydroxyl radical
What does not make covalent adducts with DNA?
bleomycin
What are the most reactive alkylation sites in the duplex DNAs?
N2 and N7
What is the most potent bis-alkylating agent?
the nitrogen mustard with two carbons between N and each Cl as well as the aromatic ring on the N to distribute the lone pair the N has
Which of the following statements about transcription is FALSE?
(A) RNA is synthesized by DNA-dependent RNA polymerase.
(B) Primer is NOT required for chain initiation.
(C) 5’-End of the chain contains triphosphate group.
(D) Both template strand and coding strand are transcribed.
(D) Both template strand and coding strand are transcribed.
Prokaryotic RNA polymerase core enzyme has the catalytic activity but does NOT recognize core promoter.
true
In prokaryotic transcription, intrinsic termination is mediated by rho factor.
false
In prokaryotic transcription, three types of RNA polymerases transcribe mRNA, tRNA, and rRNA.
false
B-DNA is a right handed helix whereas A-DNA is a left handed helix.
false
In “beads on a string” form of chromatin, level of acetylation of core histone is ____, level of histone H1 is _____, and gene transcription is _____.
high
low
likely
What nucelotides are good substrates for DNA polymerase?
dATP
deoxy triphosphate nucleotides
The DNA topoisomerase poison such as topotecan inhibits DNA scission.
false, inhibits ligation
Which of the following is NOT a biochemical function of HIV reverse transcriptase? (A) RNA-dependent DNA polymerase (B) RNA-dependent RNA polymerase (C) DNA-dependent DNA polymerase (D) Ribonuclease H
(B) RNA-dependent RNA polymerase
8 oxoguanine causes G to A transversion mutations.
false, G to T transversion
UV induced cyclobutane pyrimidine dimers (CPD) MOST frequently form between
T and T
The major modification site for nitrogen mustards and cisplatin is the N7 of guanine.
true
Bleomycin is a potent DNA-cleaving agent.
true
Inside the cell, the chloride of cisplatin is replaced by water molecule, generating LESS reactive aquated species.
false
Which is NOT a DNA intercalator?
doxorubicin, dactinomycin, mitomycin C, bleomycin
mitomycin C
___ is the most prevalent conformation for duplex DNA under physiological conditions.
B form
Highly acetylated core histones are found in “beads on a string” form of chromatin.
true
What is the best substract for DNA polymerases?
dGTP
deoxy triphosphates
The end-replication problem of eukaryotic DNA replication is solved by ____
telomerase
Topotecan inhibits topoisomerase by preventing the formation of the “cleavage complex” of topoisomerase covalently bound to DNA.
false
Which of the following does NOT belong to the biochemical functions of HIV reverse transcriptase?
RNA-dependent RNA polymerase activity
____ is the most reactive of the reactive oxygen species and attacks DNA either by adding to DNA bases or by hydrogen atoms from DNA.
hydroxyl radical
The main source of DNA lesions by reactive oxygen species is believed to involve the Fenton reaction of H2O2 with ____ complexed DNA to generate _____.
Fe (II)
hydroxyl radical
N7 methylguanine is more mutagenic than O6 methylguanine.
false
8-oxoguanine causes G to T transversion mutations.
true
UV rays induce cyclobutane pyrimidine dimers.
true
Aflatoxin B1 is a metabolically activated alkylator.
true
Inside the cell, the chloride of cisplatin is replaced by water molecule to give an inactive aquated form of cisplatin.
false
nitrogen mustards MAINLY modify N7 of guanine.
true
Nitrogen mustards undergo internal cyclization to form aziridinium ion.
true
cisplatin MAINLY modifies N7 of guanine
true
Doxorubicin alkylates N2 of guanine.
false
doxorubicin inhibits topoisomerase II
true
doxorubicin can generate free radicals.
true
doxorubicin is a strong intercalating agent
true
doxorubicin belongs to anthracyclin antibiotics
true
Which is a DNA cleaving agent?
cisplatin, dactinomycin, mitomycin C, bleomycin
bleomycin
RNA is synthesized by DNA dependent RNA polymerase
true
RNA is synthesized from 5’ to 3’ direction
true
both template strand and coding strand are transcribed.
false
Mg II is required for the nucleotidyl transfer in RNA synthesis.
true
The 5’ end of the chain contains triphosphate group.
true
In prokaryotic transcription, ____ recognizes sequences located -10 and -35 regions upstream of transcription start site.
sigma factor
Mitomycin C is a bifunctional (or bisalkylating) alkylator
true
Mitomycin C requires reductive activation.
true
Mitomycin C MAINLY alkylates N7 of guanine.
false
Anthramycin is a monofunctional or monoalkylating alkylator
true
Anthramycin MAINLY alkylates N2 of guanine.
true
Cystinuria is due to a
renal defect
The urea cycle (does/does not) occur primarily in the kidneys (as/not as) a production directly from the hydrolysis of ornithine.
does not
not as
After degradation, the carbon skeleton of leucine may be found ultimately in
palmitate
acetyl CoA
Amino acids whose carbon skeletons are converted to pyruvate include
cysteine
What forms pyruvate upon transamination?
alanine
Which amino acids are both glycogenic and ketogenic?
isoleucine
An essential amino acids includes tyrosine or tryptophan
tryptophan
Which statement concerning methionine is incorrect:
A. methionine is the principle methyl donor in the body
B. methionine is used in the biosynthesis of creatine phosphate
C. methionine can be utilized to form cysteine via serine
D. methionine is ultimately converted to propionyl-CoA when degraded
E. All of the above (A-D) are correct
All of them are correct
The hydrolysis of which amino acid in the serum forms the basis for a treatment of leukemia
asparagine
The major site for degradation of most amino acids in mammals is the
liver
