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Example Questions
Example Question #81 : Identification By Structure
Identify the given nucleotide, nucleoside or nitrogenous base.
Uridine
Cytidine
Deoxycytidine
Cytosine
Adenosine
Cytidine
This nucleoside is cytidine. If the base were not bound to the sugar, this would be cytosine. If the 2' hydroxyl group were missing, this structure would be deoxycytidine. (The 2' hydroxyl is the closest to the glycosidic bond between the base and the sugar).
Example Question #13 : Identifying Specific Nucleic Acid Structures
Which of the following composes nucleotides?
Purines, pyrimidines, pentose, nucleotide base
Nitrogenous base, phosphate, glucose
Phosphate, nitrogenous base, fructose
Pentose, nitrogenous base, phosphate
Ribose, nitrogenous base, phosphate
Pentose, nitrogenous base, phosphate
Nucleotides are formed by a pentose sugar (either ribose or deoxyribose), a nitrogenous base (adenine, cytosine, guanine, thymine, or uracil), and one or more phosphate groups. Polymers of nucleotides are known as nucleic acids (DNA and RNA).
Example Question #11 : Identifying Specific Nucleic Acid Structures
Which of the following nucleic acid bases is not in the right category?
Guanine - purine
Cytosine - pyrimidine
Uracil - purine
Adenine - purine
Thymine - pyrimidine
Uracil - purine
The pyrimidines, which contain a single six-membered ring, are uracil, cytosine, and thymine. The purines, which contain a six-membered ring and a five-membered ring, are adenine and guanine. A mnemonic to help you remember these two groups is that pyrimidines, like pyramids are sharp - and sharp things CUT (cytosine, uracil, thymine).
Example Question #141 : Identifying Biochemical Molecules
Which of the following nucleotides are purines?
Cytosine and adenine
Thymine and guanine
Adenine and cytosine
Adenine and guanine
Cytosine and thymine
Adenine and guanine
Adenine and guanine are purines, while cytosine and thymine are pyrimidines. A helpful mnemonic for this is Pure (purine) As (adenine) Gold (guanine). Note that uracil is a pyrimidine, but is only seen in RNA.
Example Question #142 : Identifying Biochemical Molecules
In the eukaryotic ribosome, the sedimentation coefficient for the small subunit is __________ and large subunit is __________.
40S . . . 70S
35S . . . 70S
60S . . . 80S
20S . . . 60S
40S . . . 60S
40S . . . 60S
The 80S eukaryotic ribosome is made up of 40S and 60S subunits.
Example Question #91 : Identification By Structure
In the prokaryotic ribosome, the sedimentation coefficient for the small subunit is __________ and large subunit is __________.
30S . . . 40S
30S . . . 50S
20S . . . 40S
40S . . . 60S
20S . . . 60S
30S . . . 50S
The 70S prokaryotic ribosome is made up of 30S and 50S subunits.
Example Question #355 : Biochemistry
Which prokaryotic translation initiation factor (IF) forms a ternary complex with mRNA, fMet-tRNA, and GTP?
IF-4
IF-3
IF-2
IF-1
IF-5
IF-2
IF-3 binds to the 30S subunit first. Then IF-2 forms the ternary complex, and it binds with IF-1 to the 30S subunit. Upon release of IF-1 and IF-3, the 50S subunit will bind to prepare for translation.
Example Question #92 : Identification By Structure
Which of the following is not considered to be a pyrimidine derivative?
Thymine
Cytosine
Guanine and adenine
Uracil
Thymine and adenine
Guanine and adenine
The nitrogenous bases that are considered to be pyrimidine derivatives are thymine, cytosine, and uracil. Thus, the purines are adenine and guanine. The mnemonic Pure As Gold (Purines = Adenine and Guanine) can be used to remember which bases are purines.
Example Question #143 : Identifying Biochemical Molecules
Which of the following components might be found in a nucleoside molecule?
I. Phosphate group
II. Pentose
III. Uracil
II and III
I and II
I only
II only
II and III
Nucleotides are monomers of nucleic acids and are made up of three molecules: nitrogenous base (uracil, thymine, cytosine, adenine or guanine), pentose sugar (deoxyribose for DNA and ribose for RNA) and phosphate group. Nucleosides, on the other hand, are molecules that only contain nitrogenous base and pentose sugar; they do not contain phosphate groups.
Example Question #26 : Identifying Specific Nucleic Acid Structures
A researcher is analyzing two nucleic acids. He observes that the molecular weight of molecule A is three times as much as molecule B. Based on the given information, which of the following can you conclude?
Molecule A has more adenine and guanine
Cannot conclude any of these based on the given information
Molecule A has uracil while molecule B doesn’t
Molecule B has more adenine and guanine
Cannot conclude any of these based on the given information
The question states that molecule A is heavier than molecule B. This could result from several reasons. First, molecule A could be a double stranded DNA and molecule B could be a single stranded RNA. This will allow the DNA molecule to be a lot heavier than its RNA counterpart. Second, molecule A could contain more purines (adenine and guanine) than molecule B). Recall that purines are two membered rings whereas pyrimidines (uracil, cytosine and thymine) are one membered rings. This means purines have more atoms and, therefore, have a higher molecular weight.
We are not given enough information to determine the identity or the distribution of nitrogenous bases in molecule A and B; therefore, we cannot conclude any of the given statements.
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