UNE BIOCHEM UNIT 4 | MULTIPLE CHOICE QUESTIONS AND ANSWERS |
VERIFIED ANSWERS (100% CORRECT) | LATEST EXAM UPDATE
Guanine is a _________________ and forms ________ hydrogen bonds with cytosine.
a)pyrimidine;2
b)purine;3
c)purine;2
d)pyrimidine;3
See Figure 12.5. - CORRECT ANSWER -Purine;3
Guanine forms 3 hydrogen bonds with cytosine and is a purine base.
Describe the structure of nucleic acids (both DNA and RNA), explaining the difference between
the constituent bases, sugars, nucleosides and nucleotides and base pairing abilities.
A nucleoside contains a:
a)a sugar and a phosphate group
b)phosphate group only
c)a nucleobase and a sugar
d)a nucleobase and a phosphate group
(Figure 12.2) - CORRECT ANSWER -c) a nuclease and a sugar
A nucleoside contains a base and a sugar group. A nucleotide contains all three portions: a base,
sugar and phosphate group.
,Define the following terms: purine, pyrimidine, nucleoside, nucleotide, nucleobase, ribose and
deoxyribose
Purine - CORRECT ANSWER -made up of two rings one 5 membered and the other 6
membered; adenine and guanine
Pyrimidine - CORRECT ANSWER -made up of one 6 member nitrogen ring; thymine,
uracil and cytosine
nucleoside - CORRECT ANSWER -just a base and a sugar
nucleotide - CORRECT ANSWER -a base, sugar and phosphate
nucleobase - CORRECT ANSWER -one of the 5 bases that comprise DNA and RNA
ribose - CORRECT ANSWER -RNA sugar
deoxyribose - CORRECT ANSWER -DNA sugar
Histone acetylation has which of the following impacts on the super structure of DNA?
a)Histone acetylation increases the association of DNA and histones
b)Histone acetylation decreases the association of DNA and histones
c)Histone acetylation has no impact on the association of DNA and histones - CORRECT
ANSWER -b)Histone acetylation decreases the association of DNA and histones
,Acetylation of histones decreases the positive charge on lysine residues within the histones. This
decreases the affinity of DNA to the histone complex. (DNA is negatively charged.)
Relate levels of histone acetylation to DNA accessibility
In the salvage of purines, HGPRT, hypoxanthine-guanine phosphoribosyl transferase is
responsible for converting:
a)adenine to adenosine monophosphate (AMP)
b)guanine to guanosine monophosphate (GMP)
c)inosine monophosphate to inosine
d)hypoxanthine to xanthine - CORRECT ANSWER -b)guanine to guanosine
monophosphate (GMP)
HGPRT is an essential enzyme in the salvage of hypoxanthine and guanine. Defects in this
enzyme lead to Lesch-Nyhan syndrome. Adenine is salvaged by APRT (B) and the conversion of
hypoxanthine to xanthine is completed by xanthine oxidase.
DNA joining complexes utilize which class of histones?
a)H3
b)H2A
c)H1
d)H2B - CORRECT ANSWER -c)H1
Explanation: nucleosome cores use four core histones: H2A, H2B, H3 and H4 while DNA join
complexes use H1.
Describe DNA superstructure and how histones facilitate supercoiling (Figure 12.3)
, Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)?
a)Aspartate Transcarbamoylase
b)Dihydrooratase
c)Thymidylate synthase
d)Carbamoyl phosphate synthetase II
See figure 40.5 - CORRECT ANSWER -c)Thymidylate synthase
Describe the biosynthesis of the purine and pyrimidine nucleotides with emphasis on the key
regulated steps
In pyrimidine synthesis, uridine triphosphate (UTP) can feedback and inhibit which of the
following enzymes?
a)Dihydrooratase
b)Thymidylate synthase
c)Carbamoyl phosphate synthase II
d)Aspartate Transcarbamoylase
See figure 41.14 - CORRECT ANSWER -c)Carbamoyl phosphate synthase II
Describe the biosynthesis of the purine and pyrimidine nucleotides with emphasis on the key
regulated steps
Which of the following is a required as an initial substrate for purine biosynthesis?
VERIFIED ANSWERS (100% CORRECT) | LATEST EXAM UPDATE
Guanine is a _________________ and forms ________ hydrogen bonds with cytosine.
a)pyrimidine;2
b)purine;3
c)purine;2
d)pyrimidine;3
See Figure 12.5. - CORRECT ANSWER -Purine;3
Guanine forms 3 hydrogen bonds with cytosine and is a purine base.
Describe the structure of nucleic acids (both DNA and RNA), explaining the difference between
the constituent bases, sugars, nucleosides and nucleotides and base pairing abilities.
A nucleoside contains a:
a)a sugar and a phosphate group
b)phosphate group only
c)a nucleobase and a sugar
d)a nucleobase and a phosphate group
(Figure 12.2) - CORRECT ANSWER -c) a nuclease and a sugar
A nucleoside contains a base and a sugar group. A nucleotide contains all three portions: a base,
sugar and phosphate group.
,Define the following terms: purine, pyrimidine, nucleoside, nucleotide, nucleobase, ribose and
deoxyribose
Purine - CORRECT ANSWER -made up of two rings one 5 membered and the other 6
membered; adenine and guanine
Pyrimidine - CORRECT ANSWER -made up of one 6 member nitrogen ring; thymine,
uracil and cytosine
nucleoside - CORRECT ANSWER -just a base and a sugar
nucleotide - CORRECT ANSWER -a base, sugar and phosphate
nucleobase - CORRECT ANSWER -one of the 5 bases that comprise DNA and RNA
ribose - CORRECT ANSWER -RNA sugar
deoxyribose - CORRECT ANSWER -DNA sugar
Histone acetylation has which of the following impacts on the super structure of DNA?
a)Histone acetylation increases the association of DNA and histones
b)Histone acetylation decreases the association of DNA and histones
c)Histone acetylation has no impact on the association of DNA and histones - CORRECT
ANSWER -b)Histone acetylation decreases the association of DNA and histones
,Acetylation of histones decreases the positive charge on lysine residues within the histones. This
decreases the affinity of DNA to the histone complex. (DNA is negatively charged.)
Relate levels of histone acetylation to DNA accessibility
In the salvage of purines, HGPRT, hypoxanthine-guanine phosphoribosyl transferase is
responsible for converting:
a)adenine to adenosine monophosphate (AMP)
b)guanine to guanosine monophosphate (GMP)
c)inosine monophosphate to inosine
d)hypoxanthine to xanthine - CORRECT ANSWER -b)guanine to guanosine
monophosphate (GMP)
HGPRT is an essential enzyme in the salvage of hypoxanthine and guanine. Defects in this
enzyme lead to Lesch-Nyhan syndrome. Adenine is salvaged by APRT (B) and the conversion of
hypoxanthine to xanthine is completed by xanthine oxidase.
DNA joining complexes utilize which class of histones?
a)H3
b)H2A
c)H1
d)H2B - CORRECT ANSWER -c)H1
Explanation: nucleosome cores use four core histones: H2A, H2B, H3 and H4 while DNA join
complexes use H1.
Describe DNA superstructure and how histones facilitate supercoiling (Figure 12.3)
, Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)?
a)Aspartate Transcarbamoylase
b)Dihydrooratase
c)Thymidylate synthase
d)Carbamoyl phosphate synthetase II
See figure 40.5 - CORRECT ANSWER -c)Thymidylate synthase
Describe the biosynthesis of the purine and pyrimidine nucleotides with emphasis on the key
regulated steps
In pyrimidine synthesis, uridine triphosphate (UTP) can feedback and inhibit which of the
following enzymes?
a)Dihydrooratase
b)Thymidylate synthase
c)Carbamoyl phosphate synthase II
d)Aspartate Transcarbamoylase
See figure 41.14 - CORRECT ANSWER -c)Carbamoyl phosphate synthase II
Describe the biosynthesis of the purine and pyrimidine nucleotides with emphasis on the key
regulated steps
Which of the following is a required as an initial substrate for purine biosynthesis?
