Exam 4 Practice Exams

Question 1

Which of the following is false regarding the urea cycle?

a. The synthesis of carbamoyl phosphate requires ATP, bicarbonate and a source of nitrogen.
b. The purines guanine and adenine are used as a source of nitrogen in this pathway.
c. NH3 from glutamine or ammonia is one source of nitrogen used to produce urea.
d. This pathway utilizes both cytoplasmic and mitochondrial enzymes.

Answer 1

b. The purines guanine and adenine are used as a source of nitrogen in this pathway.

Question 2

During the de novo synthesis of purines, the purine bases are formed first, and then are attached as a whole, whereas pyrimidine bases are built, piece-by-piece on the activated ribosyl platform.

a. True
b. False

Answer 2

b. False

Question 3

Please choose the true statement:

a. The pyrimidines found in nucleic acid are uracil, thymine and cytosine.
b. The pyrimidines found in nucleic acid are guanine, thymine and cytosine.
c. The purines found in nucleic acid are guanine and cytosine.
d. The purines found in nucleic acid are glycine and alanine

Answer 3

a. The pyrimidines found in nucleic acid are uracil, thymine and cytosine.

Question 4

In an experiment, the tRNA that carries aspartate was correctly charged with aspartate. This aspartate was then chemically altered, through amination, to become asparagine. The result is that the tRNA that normally carries Asp, is now carrying Asn. To which mRNA codon, shown below, would this tRNA most likely bind?

a. GAC
b. AAC
c. CAG
d. CAA

Answer 4

a. GAC

Question 5

Please select the false statement:

a. Phenylalanine and tryptophan can be used to produce both glucose and ketone bodies.
b. U1, U2, U4, U5 and U6 snRNPs, which are comprised of protein and RNA, are splicing factors.
c. Glutamine synthetase uses glutamate, ATP, and ammonium to produce glutamine.
d. The enzyme glutamate dehydrogenase forms L-glutamate from oxaloacetate and ammonium.

Answer 5

d. The enzyme glutamate dehydrogenase forms L-glutamate from oxaloacetate and ammonium.

Question 6

Please select the true statement:

a. Urate is produced during amino acid catabolism, and is eliminated in the urine.
b. Lack of sufficient urate in the blood, caused by a deficiency in xanthine oxidase, causes gout.
c. Humans and other primates eliminate nitrogenous waste as allantoin.
d. Urate is a potent antioxidant.

Answer 6

d. Urate is a potent antioxidant.

Question 7

Please select the false statement regarding PKU:

a. Phenylketonuria generally results from a dysfunction in the enzyme phenylalanine hydroxylase or a deficit in the cofactor tetrahydrobiopterin.
b. Phenylketonuria can cause profound cognitive impairment if not treated within the first year of life.
c. Phenylketonuria is caused by a recessive autosomal defect.
d. Persons with PKU must reduce their intake of tyrosine throughout their life compared to persons without PKU

Answer 7

d. Persons with PKU must reduce their intake of tyrosine throughout their life compared to persons without PKU

Question 8

Cis factors would be most likely to be degraded by proteases, whereas trans factors would be most likely to be degraded by nucleases.

a. True
b. False

Answer 8

b. False

Question 9

Which intermediate is not one of the seven common metabolites of protein degradation?

a. Pyruvate
b. Oxaloacetate
c. Citrate
d. Acetyl CoA

Answer 9

c. Citrate

Question 10

Which of the following could be bound to DNA during initiation of transcription in eukaryotes:

a. Lac repressor
b. TFIID
c. sigma factor
d. Rec A

Answer 10

b. TFIID

Question 11

Please select the true statement to show what enzyme synthesizes each product.

a. RNA Pol II: mRNA; RNA Pol I: most rRNA; RNA Pol III: tRNA
b. RNA Pol I: mRNA; RNA Pol II: most rRNA; RNA Pol III: tRNA
c. RNA Pol II: mRNA; RNA Pol III: most rRNA, RNA Pol I: tRNA
d. RNA Pol III: mRNA; RNA Pol II: most rRNA; RNA Pol II: tRNA

Answer 11

a. RNA Pol II: mRNA; RNA Pol I: most rRNA; RNA Pol III: tRNA

Question 12

The first committed step of glycolysis is:

a. Catalyzed by hexokinase
b. Up-regulated by fructose 2,6-BP
c. Up-regulated by glucagon.
d. Up-regulated by glucose 6-phosphate

Answer 12

b. Up-regulated by fructose 2,6-BP

Question 13

Please select the false statement about transcription factors:

a. Zinc fingers bind the DNA major groove and require zinc metals coordinated to His and/or Cys.
b. Each B-zip protein is a single helix that binds DNA and forms a homo or hetero dimer to effect transcription.
c. CAP binds DNA in bacterial cells when there are low concentrations of lactose available.
d. Homeodomain proteins are eukaryotic transcription factors with helix-turn-helix motifs

Answer 13

a. Zinc fingers bind the DNA major groove and require zinc metals coordinated to His and/or Cys.

Question 14

If there were no lactose and no glucose present, what would be the state of the lac operon:

a. Transcription of the lac genes would be repressed.
b. Transcription of the lac genes would be present at basal levels.
c. Transcription of the lac genes would be present at activated levels.
d. There is no correct answer here

Answer 14

a. Transcription of the lac genes would be repressed.

Question 15

Please select the true statement:

a. Deamination of guanine forms uracil.
b. The factors present at the initiation site prior to the start of transcription in E. coli are: TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH.
c. TFIIH has helicase and kinase activities that are necessary for promoter escape.
d. The UP sequence is found upstream of transcripts that are rarely used

Answer 15

c. TFIIH has helicase and kinase activities that are necessary for promoter escape.

Question 16

Please select the false statement

a. Bacterial genes can be transcribed and translated at the same time
b. RNA is more resistant to hydrolytic damage than DNA because RNA is reduced at the 2’ position whereas DNA is not.
c. Eukaryotic chromosomes have many origins of replication
d. Telomerase has a reverse transcriptase function.

Answer 16

b. RNA is more resistant to hydrolytic damage than DNA because RNA is reduced at the 2’ position whereas DNA is not.

Question 17

Histone deacetylases (HDACs) increase the accessibility of DNA to transcriptional machinery by removing acetyl groups from acetylated histones.

a. True
b. False

Answer 17

b. False

Question 18

Which statement correctly describes the first committed step in the de novo synthesis of purines:

a. This step is requires the amino group from glutamine.
b. This step is catalyzed by PRPP hydroxylase.
c. This step phosphorylates Ribose1-Phosphate to make PRPP.
d. This step transfers hypoxanthine to PRPP.

Answer 18

a. This step is requires the amino group from glutamine

Question 19

Please select the true statement:

a. DNA Pol III is a eukaryotic DNA polymerase that synthesizes DNA during replication.
b. DNA ligase is an enzyme that works by transesterfication and does not require ATP.
c. The RNA in Okazaki fragments in prokaryotes is removed by Pol ∂.
d. RNA primer synthesis is necessary during replication in eukaryotes and E.coli.

Answer 19

d. RNA primer synthesis is necessary during replication in eukaryotes and E.coli.

Question 20

The urea cycle is highly active in muscles.

a. True
b. False.

Answer 20

b. False.

Question 21

Please select the true statement regarding pyridoxal phosphate:

a. This cofactor is required for all aminotransferases.
b. This cofactor is a derivative of folic acid.
c. This cofactor transfers CO2 during amino acid catabolism.
d. None of the above are true.

Answer 21

a. This cofactor is required for all aminotransferases.

Question 22

Which of the following intermediates can be used to make glucose in humans?

a. Alanine
b. Lysine
c. Acetyl CoA
d. Leucine

Answer 22

a. Alanine

Question 23

Changing CCC to CGC creates a transversion mutation.

a. True
b. False

Answer 23

a. True

Question 24

Please select the true statement:

a. The mRNA template is read in the 3’ – 5’direction during translation.
b. In bacteria and eukaryotes, mRNA is synthesized in the 3’ – 5’direction.
c. The DNA template is read in the 3’ – 5’ direction during transcription.
d. There are no true answers here.
e. Both a and c are true

Answer 24

c. The DNA template is read in the 3’ – 5’ direction during transcription.

Question 25

Please select the true statement:

a. PCNA is a primase that functions to unwind the DNA helix during replication in E. coli.
b. The polymerases, alpha (α), and epsilon (ε), are the major eukaryotic RNA polymerases.
c. Ribonucleotide reductase is regulated by phosphorylation, which down-regulates the enzyme.
d. High concentrations of ATP upregulate the overall activity of ribonucleotide reductase

Answer 25

d. High concentrations of ATP upregulate the overall activity of ribonucleotide reductase

Question 26

Lesch-Nhyan syndrome is a fatal disease caused by an inability to break down branched chain amino acids.

a. True
b. False

Answer 26

b. False

Question 27

Please select the true statement:

a. In the purine salvage pathway, the enzyme HGPRT transfers hypoxanthine and glycine to PRPP.
b. Alcaptonuria is caused by overabundance of homogentisate, which is released in the urine.
c. Pyrimidine synthesis is up regulated by the allosteric effect of ATP and downregulated by the allosteric effect of CTP on the enzyme aspartate transcarbamoylase.
d. All the above are true.
e. Only b and c are true

Answer 27

e. Only b and c are true

Question 28

Which intermediate is formedfrom argininosuccinate in the urea cycle, and links the urea cycle with the TCA cycle?

a. Succinyl CoA
b. Malate
c. Fumarate
d. Succinate

Answer 28

c. Fumarate

Question 29

Trans factors bind to silencers to reduce transcription, or enhancers to increase transcription.

a. True
b. False

Answer 29

a. True

Question 30

Inosine monophosphate is an intermediate in the pyrimidine synthetic pathway.

a. True
b. False

Answer 30

b. False

Question 31

Here is a short segment of DNA. Please correctly translate this coding sequence: 5’GATGCCGAGCACA3’

Answer 31

Met Pro Ser Thr

Question 32

Please write the enzyme that catalyzes the first committed step in the following pathways (not the reaction):
Fatty acid synthesis:

Answer 32

Acetyl CoA carboxylase

Question 33

Please write the enzyme that catalyzes the first committed step in the following pathways (not the reaction):
Fatty acid degradation:

Answer 33

Carnitine Acyl-transferase

Question 34

If DNA representing one chromosome were extracted from E coli and also from a dog, please name one feature that you could identify to determine which was which. You have a huge group of grad students, access to any reagent possible, and plenty of lab equipment to help you

Answer 34

Dog: linear, many origins of replication, centromere, telomeres. Absence of lac operon (or something similar)

E. coli: circular, one origin of replication, no centromere or telomeres. Presence of lac operon (or something similar)

Question 35

Each bacterial genome has one chromosome and one origin of replication, while each eukaryotic genome has many chromosomes, each of which has more than one origin of replication per chromosome.

a. True
b. False

Answer 35

a. True

Question 36

Folate synthesis is a process that occurs in bacteria but not in humans, and is inhibited by sulfonamides, a class of antibiotic that resembles the intermediate PABA (para-aminobenzoic acid).

a. True
b. False

Answer 36

a. True

Question 37

Please choose the true statement:

a. During replication, the DNA template is read in the 3’ to 5’ direction.
b. During replication, both strands of DNA are polymerized in the 3’ to 5’ direction.
c. During replication, the DNA template is read in the 5’ to 3’ direction.
d. During replication, the DNA leading strand is polymerized in the 5’ to 3’ direction, but the lagging strand is polymerized in the 3’ to 5’ direction

Answer 37

a. During replication, the DNA template is read in the 3’ to 5’ direction.

Question 38

Please choose the correct pairing:

a. Lesch–Nyhan syndrome: Defect in purine catabolism.
b. Severe combined immunodeficiency: Defect in the salvage pathway of purines.
c. Gout: Defect in pyrimidine synthesis
d. Huntingdon’s disease: Expansion of Tri-deoxynucleotide CAG repeats.

Answer 38

d. Huntingdon’s disease: Expansion of Tri-deoxynucleotide CAG repeats.

Question 39

Please choose the true statement:

a. The pyrimidines found in nucleic acid are guanine, thymine and cytosine.
b. The pyrimidines found in nucleic acid are uracil, thymine and cytosine.
c. The purines found in nucleic acid are guanine and cytosine.
d. The purines found in nucleic acid are glycine and alanine.

Answer 39

b. The pyrimidines found in nucleic acid are uracil, thymine and cytosine.

Question 40

Please choose correct parings of enzyme and product:

a. RNA Pol I: mRNA, RNA Pol II: rRNA, RNA Pol III: tRNA and rRNA.
b. RNA Pol I: rRNA, RNA Pol II: tRNA, RNA Pol III: mRNA.
c. RNA Pol I: tRNA, RNA Pol II: rRNA, RNA Pol III: mRNA.
d. RNA Pol I: tRNA, RNA Pol II: mRNA, RNA Pol III: tRNA and rRNA.
e. There are no correct statements.

Answer 40

e. There are no correct statements.

Question 41

Please select the true statement regarding Pol δ, and Pol ε

a. These are RNA polymerases in prokaryotes such as bacteria.
b. These are DNA polymerases in prokaryotes such as bacteria.
c. These are RNA polymerases in eukaryotes such as yeast.
d. These are DNA polymerases in eukaryotes such as yeast.

Answer 41

d. These are DNA polymerases in eukaryotes such as yeast.

Question 42

Which enzyme polymerizes the primer during replication in eukaryotes?

a. Pol α
b. Pol δ
c. Pol ε
d. Pol I
e. Pol II
f. Pol III
g. Sigma factor

Answer 42

a. Pol α

Question 43

Please choose the true statement:

a. The conformation of Z-DNA is a right-handed helix and is generated largely by runs of alternating purines and pyrimidines.
b. The conformation of A-DNA is a left-handed helix and is the most common DNA conformation.
c. U1, U2, U4, U5 and U6 snRNPs are comprised of protein and RNA and are components of the splicing machinery.
d. tRNA is comprised exclusively of single-stranded RNA.
e. 5S RNA is a component of DNA polymerase alpha and is used for sequence recognition

Answer 43

c. U1, U2, U4, U5 and U6 snRNPs are comprised of protein and RNA and are components of the splicing machinery.

Question 44

Please choose the true statement: Please note that prior may not mean immediately prior

a. In the de novo synthesis of purines, the intermediate orotate is formed prior to the synthesis of inosine monophosphate.
b. In the de novo synthesis of pyrimidines, orotate is formed prior to the synthesis of inosine monophosphate.
c. In the de novo synthesis of pyrimidines, orotate is formed prior to the synthesis of uridylate (also called uridine monophosphate, UMP).
d. There are no true statements here.

Answer 44

c. In the de novo synthesis of pyrimidines, orotate is formed prior to the synthesis of uridylate (also called uridine monophosphate, UMP).

Question 45

Please choose the true statement regarding Phenylketonuria:

a. This condition is caused by an overabundance of active phenylalanine hydroxylase.
b. This condition may be caused by a deficiency in the cofactor tetrahydrofolate.
c. This condition can lead to severe neurological and cognitive deficits if untreated within the first year of life.
d. This condition is a result of a defect in the catabolism of tyrosine.
e. Only b and c are true.

Answer 45

c. This condition can lead to severe neurological and cognitive deficits if untreated within the first year of life.

Question 46

Please choose the false statement regarding inborn errors of amino acid metabolism:

a. Alkaptonuria results from a mutation in the gene for homogentisate oxygenase.
b. Alkaptonuria is a lethal condition that results from a defect in phenylalanine and tyrosine catabolism.
c. Maple-syrup urine disease is a defect or deficit in the enzyme branched-chain dehydrogenase, an enzyme that catalyzes the catabolism of branched chain amino acids.
d. In the condition, maple-syrup urine disease, oxidative decarboxylation of α-ketoacids from amino acids like isoleucine, valine and leucine does not occur, and so these ketoacids and branched chain amino acids build up, causing severe cognitive disability and overall failure to thrive.

Answer 46

b. Alkaptonuria is a lethal condition that results from a defect in phenylalanine and tyrosine catabolism.

Question 47

Please choose the true statement regarding pyridoxal phosphate:

a. This cofactor contains a reactive aldehyde connected to pyrimidine ring
b. This cofactor contains an aldehyde, which can make a protonated Shiff base with epsilon-amino groups from lysine or with alpha-amino groups from amino acids during transaminations.
c. This cofactor is present and necessary in all aminotransferases.
d. All the above are true
e. Only b and c are true.

Answer 47

d. All the above are true

Question 48

The release of CO2 from PRPP (5-phosphoribosyl 1-pyrophosphate) provides the driving force for the initial step of nucleotide synthesis

a. True
b. False

Answer 48

b. False

Question 49

Which intermediate is not one of the seven common metabolites of protein degradation?

a. Pyruvate
b. Succinyl CoA
c. Oxaloacetate
d. Fumarate
e. Citrate
f. Acetyl CoA

Answer 49

e. Citrate

Question 50

Which intermediate is a metabolite that is correctly paired with its possible fate.

a. Threonine: Both Glucose and Ketone bodies
b. Lysine: Glucose but NOT ketone bodies
c. Isoleucine: Ketone bodies but NOT glucose
d. Tryptophan: Both Glucose and Ketone bodies

Answer 50

d. Tryptophan: Both Glucose and Ketone bodies

Question 51

Histone deacetylases (HDACs) increase accessibility of the DNA to transcriptional machinery by removing acetyl groups from acetylated histones.

a. True
b. False

Answer 51

b. False

Question 52

What pathways are involved in the biosynthesis of fatty acids.

a. Phosphofructokinase 1
b. Pyruvate carboxykinase
c. Glucose 6-phosphate Dehydrogenase
d. Carnitine acyltransferase I
e. Acetyl CoA Carboxylase
f. Carbamate synthetase
g. Isocitrate dehydrogenase

Answer 52

e. Acetyl CoA Carboxylase

Question 53

What pathways are involved in the degradation of fatty acids:

a. Phosphofructokinase 1
b. Pyruvate carboxykinase
c. Glucose 6-phosphate Dehydrogenase
d. Carnitine acyltransferase I
e. Acetyl CoA Carboxylase
f. Carbamate synthetase
g. Isocitrate dehydrogenase

Answer 53

d. Carnitine acyltransferase I

Question 54

What pathways are involved in Glycolysis:

a. Phosphofructokinase 1
b. Pyruvate carboxykinase
c. Glucose 6-phosphate Dehydrogenase
d. Carnitine acyltransferase I
e. Acetyl CoA Carboxylase
f. Carbamate synthetase
g. Isocitrate dehydrogenase

Answer 54

a.Phosphofructokinase 1

Question 55

What pathways are involved in gluceoneogenesis.

a. Phosphofructokinase 1
b. Pyruvate carboxykinase
c. Glucose 6-phosphate Dehydrogenase
d. Carnitine acyltransferase I
e. Acetyl CoA Carboxylase
f. Carbamate synthetase
g. Isocitrate dehydrogenase

Answer 55

b. Pyruvate carboxykinase

Question 56

What pathways are involved in the oxidative pentose phosphate pathway.

a. Phosphofructokinase 1
b. Pyruvate carboxykinase
c. Glucose 6-phosphate Dehydrogenase
d. Carnitine acyltransferase I
e. Acetyl CoA Carboxylase
f. Carbamate synthetase
g. Isocitrate dehydrogenase

Answer 56

c. Glucose 6-phosphate Dehydrogenase

Question 57

Please select the false statement:

a. In the purine salvage pathway, HGPRT, and APRT transfer a salvaged purine base to a PRPP platform.
b. Pyrimidines are synthesized strictly de novo, as there is no pyrimidine salvage pathway.
c. Enteropeptidase is a protease that cleaves tripsinogen to form the active trypsin.
d. The enzyme photolyase is not found in humans

Answer 57

b. Pyrimidines are synthesized strictly de novo, as there is no pyrimidine salvage pathway.

Question 58

Please select the true statement:

a. In purine synthesis, dUMP s formed before UMP.
b. Tetrahydrofolate is a folate derivative that is necessary for thymidylate synthesis.
c. The suicide inhibitor, fluorouracil, inhibits thymidylate synthase.
d. All the above are true
e. Only b and c are true.

Answer 58

e. Only b and c are true.

Question 59

The transamination of alanine to alpha-ketoglutarate yields pyruvate and glutamate.

a. True
b. False

Answer 59

a. True

Question 60

Please choose the true statement:

a. The basal transcription factors present at the initiation site prior to the start of transcription of pol II transcripts in eukaryotes are: TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH.
b. TFIIH has the helicase and kinase activity necessary for promoter escape.
c. The UP sequence is found upstream of transcripts that are used frequently, such as tRNAs.
d. All the above are true.
e. Only b and c are true.

Answer 60

d. All the above are true.

Question 61

Please choose the true statement:

a. Deamination of the base, cytosine, yields uracil.
b. DNA is more resistant to hydrolytic damage than RNA because DNA is reduced at the 2’ position whereas RNA is not.
c. Cdc6 and Ctd1 and Mcm2-7, are eukaryotic licensing factors.
d. The binding domains of homoedomain proteins and the lac repressor are helix-turn-helix domains (also known as helix-loop-helix domains)
e. all the above are true.
f. only a and c are true.

Answer 61

e. all the above are true.

Question 62

Please select the true statement:

a. In eukaryotic replication, the main polymerase is DNA Pol Ι.
b. The severity of symptoms in patients with Huntington’s syndrome, and fragile X syndrome tends to be lessened from generation to generation, and the age of onset increases in a process called depreciation.
c. EF-Tu is an elongation factor that brings tRNA, charged with its amino acid, to the template in the ribosome.
d. If you change the amino acid that is loaded on a tRNA, the tRNA will recognize the new amino acid and bind to the codon that corresponds to that new amino acid

Answer 62

c. EF-Tu is an elongation factor that brings tRNA, charged with its amino acid, to the template in the ribosome

Question 63

Please select the false statement:

a. The polymerization of DNA requires a primer with a free 3’ hydroxyl.
b. E.coli can resolve thymine dimers directly through action of the enzyme, photolyase which uses light energy to break the thymine-thymine bond.
c. The telomerase enzyme carries an RNA template for the synthesis of telomeres.
d. Without telomerase activity, linear chromosomes would shorten with each round or replication.
e. There are no false answers here

Answer 63

e. There are no false answers here

Question 64

During replication, polymerization from the leading strand template is continuous, while polymerization from the lagging strand occurs in short 5’>3’ fragments called Okazaki fragments.

a. True
b. False

Answer 64

a. True

Question 65

What intermediate links the urea cycle & TCA cycle?

Answer 65

Fumarate

Question 66

Catabolite activated protein (CAP) is bound by what small molecule?

Answer 66

cAMP

Question 67

Please write the reaction for the addition of a ribonucleotide to an RNA chain as catalyzed by RNA polymerase, and remember to include all reactants and products.

Answer 67

NTP + RNA -> Polymerase enzyme yields RNA + one more NT PPi

This PPi is hydrolyzed immediately to 2 Pi and is the driving force for this reaction

Question 68

you have mutated the lac operon so that the Lac repressor will no longer bind. What would be the level of β-galactosidase production with high glucose levels. Please answer by using the following choices:

a. Expressed, but at basal levels
b. Activated above basal activity
c. Repressed

Answer 68

a. Expressed, but at basal levels

Question 69

you have mutated the lac operon so that the Lac repressor will no longer bind. What would be the level of β-galactosidase production with low glucose levels. Please answer by using the following choices:

a. Expressed, but at basal levels
b. Activated above basal activity
c. Repressed

Answer 69

b. Activated above basal activity