Biochemistry : Biochemistry
Study concepts, example questions & explanations for Biochemistry
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Example Questions
Example Question #135 : Identifying Biochemical Molecules
Identify the given nucleotide, nucleoside or nitrogenous base.
Adenosine-5-triphosphate
Adenine triphosphate
Adenosine-5-phosphate
Adenine-5-triphosphate
Adenosine triphosphate
Adenosine-5-triphosphate
This nucleotide is adenosine-5-triphosphate, also known as ATP. When the nitrogenous base adenine is bound to a sugar, it becomes a nucleoside called adenosine. The carbon in the ribose at the site of the glycosidic bond is referred to as the 1' carbon. If we count clockwise, we will see that the phosphates are bound at the 5' carbon. Because there are three phosphate groups bound, the nomenclature must be 5-triphosphate.
Example Question #351 : Biochemistry
Identify the given nucleotide, nucleoside or nitrogenous base.
Deoxycytidine
Uridine
Adenosine
Cytidine
Cytosine
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 
Example Question #17 : Identifying Specific Nucleic Acid Structures
Which of the following composes nucleotides?
Pentose, nitrogenous base, phosphate
Phosphate, nitrogenous base, fructose
Nitrogenous base, phosphate, glucose
Ribose, nitrogenous base, phosphate
Purines, pyrimidines, pentose, nucleotide base
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 #18 : Identifying Specific Nucleic Acid Structures
Which of the following nucleic acid bases is not in the right category?
Thymine - pyrimidine
Adenine - purine
Cytosine - pyrimidine
Uracil - purine
Guanine - purine
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 #21 : Identifying Specific Nucleic Acid Structures
Which of the following nucleotides are purines?
Cytosine and thymine
Thymine and guanine
Adenine and guanine
Cytosine and adenine
Adenine and cytosine
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 #22 : Identifying Specific Nucleic Acid Structures
In the eukaryotic ribosome, the sedimentation coefficient for the small subunit is __________ and large subunit is __________.
60S . . . 80S
40S . . . 60S
35S . . . 70S
20S . . . 60S
40S . . . 70S
40S . . . 60S
The 80S eukaryotic ribosome is made up of 40S and 60S subunits.
Example Question #23 : Identifying Specific Nucleic Acid Structures
In the prokaryotic ribosome, the sedimentation coefficient for the small subunit is __________ and large subunit is __________.
40S . . . 60S
20S . . . 40S
20S . . . 60S
30S . . . 40S
30S . . . 50S
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 #24 : Identifying Specific Nucleic Acid Structures
Which of the following is not considered to be a pyrimidine derivative?
Guanine and adenine
Thymine and adenine
Uracil
Cytosine
Thymine
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 #25 : Identifying Specific Nucleic Acid Structures
Which of the following components might be found in a nucleoside molecule?
I. Phosphate group
II. Pentose
III. Uracil
II only
II and III
I and II
I 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.
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