Previous Biochem Exams 1-3 Flashcards by Rachel Willauer

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

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Which molecules will be fund in mixed micelles of the intestines following digestion of a typical meal?

cholesterol

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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

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What is false regarding lipid metabolism?

more than 25% of dietary cholesterol is in esterified form

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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

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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

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What tissue is primarily involved in the synthesis of chylomicrons?

small intestinal epithelium

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Which enzyme initially hydrolyzes dietary triacylgycerides containing short chain immediately after ingestion?

gastric lipase

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All fatty acids require assistance by mixed micelles for absorption by intestinal mucosa.

false

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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

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What is the closest percentage of cholesterol molecules that are deprotonated at physiological pH?

0.01%

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What is the correct protein composition of lipoproteins in order from highest to lowest ratio of protein to lipid?

HDL > LDL > IDL > VLDL > chylomicron

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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

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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

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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

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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

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Which enzyme hydrolyzes dietary triacylglycerides containing short chain fatty acids immediately after ingestion?

lingual lipase

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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

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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

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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

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What is the primary site of the synthesis of IDLs?

vascular endothelium

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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

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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

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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

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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