Effective practice materials for Metabolism class. All of them are hand made and chose specifically to strengthen understanding or to enforce passive memory of the content. These materials are good for cramming when short in time.
ic acid may be absorbed as intact nucleotides, the majority of it is absorbed as nucleosides.
1. What is the primary form in which dietary nucleic acids are absorbed?
a) Nucleotides
b) Nucleosides
c) Phosphodiester bonds
d) Purines and pyrimidines
e) Ribose and deoxyribose sugars
Answer: b) Nucleosides.
Explanation: The products of nucleic acid digestion are monophosphate nucleotides, which are then
acted on by phosphatases to produce nucleosides. The majority of dietary nucleic acids are absorbed
as nucleosides.
2. Why is there essentially no dietary requirement for nucleic acids?
a) We have the ability to make all of the purines and pyrimidines that we need.
b) Nucleic acids are too complex to be absorbed by the body.
c) We do not ingest enough nucleic acids to meet our daily requirements.
d) Nucleic acids are harmful to the body.
e) None of the above.
Answer: a) We have the ability to make all of the purines and pyrimidines that we need.
Explanation: We have the synthetic pathways to make as much of the building blocks for DNA and RNA
as we need, including all of the purines and pyrimidines.
3. What is the first step in nucleic acid digestion?
a) Removal of phosphate groups
b) Hydrolysis of phosphodiester bonds
c) Absorption as nucleosides
d) Production of monophosphate nucleotides
e) None of the above.
Answer: b) Hydrolysis of phosphodiester bonds.
Explanation: The first thing that happens in nucleic acid digestion is that the nucleases hydrolyze the
phosphodiester bonds that connect the individual nucleotides together.
,ase, a pentose sugar, and one or more phosphate groups. Nucleosides, on the other hand, lack the
phosphate group(s) and only have the nitrogenous base and sugar components.
1. What are nucleosides?
a) Molecules that have a purine or pyrimidine molecule linked to a ribose or deoxyribose sugar
b) Molecules that have a phosphate group, a nitrogenous base, and a pentose sugar
c) Molecules that have a nitrogenous base and a phosphate group
d) Molecules that have a nitrogenous base and a sugar component
e) Molecules that have a phosphate group and a sugar component
Answer: a) Molecules that have a purine or pyrimidine molecule linked to a ribose or deoxyribose sugar
Explanation: Nucleosides are molecules that have a purine or pyrimidine molecule linked to a ribose or
deoxyribose sugar.
2. What happens to most of the nucleosides that are absorbed into the enterocyte?
a) They are acted on by nucleosidases which hydrolyze the linkage between the sugar and nitrogenous
base
b) They are reutilized for nucleic acid synthesis
c) They are further degraded after being absorbed
d) They are used by the rapidly regenerating enterocytes
e) They are excreted from the body
Answer: c) They are further degraded after being absorbed
Explanation: Most of the nucleosides that are absorbed into the enterocyte are further degraded after
being absorbed.
3. What percentage of the nucleosides that are absorbed are reutilized for nucleic acid synthesis?
a) 5%
b) 10%
c) 25%
d) 50%
e) 75%
, Answer: a) 5%
Explanation: Only about 5% of the nucleosides that are absorbed are reutilized for nucleic acid
synthesis.
4. Where do almost all of the nucleotides that we need for nucleic acid synthesis come from?
a) Dietary sources
b) Biosynthetic pathways present in our cells
c) Both dietary sources and biosynthetic pathways present in our cells
d) The liver
e) The kidneys
Answer: b) Biosynthetic pathways present in our cells
Explanation: Almost all of the nucleotides that we need for nucleic acid synthesis come from
biosynthetic pathways present in our cells and not from dietary sources.
5. What is the difference between nucleotides and nucleosides?
a) Nucleotides lack the phosphate group(s) and only have the nitrogenous base and sugar
components, while nucleosides have a nitrogenous base, a pentose sugar, and one or more phosphate
groups.
b) Nucleotides have a purine or pyrimidine molecule linked to a ribose or deoxyribose sugar, while
nucleosides have a nitrogenous base and a sugar component.
c) Nucleotides have a nitrogenous base and a phosphate group, while nucleosides lack the phosphate
group(s) and only have the nitrogenous base and sugar components.
d) Nucleotides have a nitrogenous base and a sugar component, while nucleosides have a purine or
pyrimidine molecule linked to a ribose or deoxyribose sugar.
e) Nucleotides have a phosphate group and a sugar component, while nucleosides have a nitrogenous
base and a phosphate group.
Answer: c) Nucleotides have a nitrogenous base and a phosphate group, while nucleosides lack the
phosphate group(s) and only have the nitrogenous base and sugar components.
Explanation: Nucleotides have a nitrogenous base and a phosphate group, while nucleosides lack the
phosphate group(s) and only have the nitrogenous base and sugar components.
Question: Which of the following is NOT a nitrogenous base found in nucleotides?
A) Adenine
B) Guanine
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